JPH11258507A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which is miniaturized and whose cost is reduced. SOLUTION: A first group G1 which has positive refractive force and which is fixed at the time of power varying, a second group G2 which has negative refractive force and which moves from an object-side to an image surface-side from a wide angle end to a telephoto end at the time of power varying, a third group G3 which has positive refractive force and which moves from the image surface-side to the object-side from the wide angle end to the telephoto end at the time of power varying and a fourth group G4 which has positive refractive force and can be moved at the time of power varying are installed in order from the object-side. A condition expression 0.5<|F2 /F3 |<1.2 (F1 represents the focal distance of i-th group) on the power of the third group G3, a condition expression 0.49<|L3 /L2 |<1 (L1 represents the moving quantity of i-th group from wide angle end to telephoto end) on the moving quantity of the third group G3 at the time of power varying or a condition expression 2<(F3.4 )/IH<3.3 ((F3.4 ) represents synthesis focal distance of third group and fourth group at wide angle end and IH represents a image circle radius) on the synthesis power of the third group G3 and the fourth group G4 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to a small and low-cost zoom lens for a camera using electronic image pickup means such as a camcorder and a digital camera.

[0002]

2. Description of the Related Art Conventionally, zoom lenses in this field, which have been reduced in size and cost for consumer use, are disclosed in JP-A-4-43311 and JP-A-4-7.
As shown in No. 8806, it is composed of four groups of positive, negative, positive and positive in order from the object side, the first and third groups are fixed at the time of zooming, and the negative second group is on the optical axis. Move to zoom,
There has been proposed a lens arrangement in which the fourth unit moves on the optical axis so as to correct a change in the image plane position caused by zooming. On the contrary,
As shown in JP-A-6-99497 and JP-A-6-194572, the third lens unit moves from the image plane side to the object side from the wide-angle end to the telephoto end to assist the zooming operation, thereby further reducing the size. There is something that aimed at. These show zoom lenses having a relatively high zoom ratio of about 8 to 12 times. By the way, when a lens system having a small zoom ratio is considered with an emphasis on downsizing and cost reduction of the lens system, the examples shown therein have a large number of components, and the miniaturization is not yet sufficient.

Incidentally, the zoom lens disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 6-94997 and 6-194572 has a large part of the zooming function of the second lens group. In this case, in order to keep the image point substantially constant, the lateral magnification of the second lens unit must be in the range of about -1 from the wide-angle end to the telephoto end. However, in order to further reduce the zoom ratio by setting the variable power ratio smaller than this, the movement amount of the second lens group can be small.
It is efficient that the space between groups is tightly packed for miniaturization.

However, in order for the second lens unit to take a lateral magnification of about -1 in a state where the distance between the first lens unit and the second lens unit is reduced, the power of the first lens unit with respect to the second lens unit must be increased. Must. As a result, the entrance pupil becomes farther, the height of off-axis rays passing through the first group increases, and the lens system of the first group increases in size. Accordingly, the thickness of the lenses of the first group also increases. In addition, since the curvature of each lens of the first group must be increased, the thickness of the first group lens increases in order to secure the edge (edge) of the lens.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide a zoom lens suitable for further miniaturization and cost reduction with respect to the conventional example. To provide.

One of the specific objects of the present invention is to provide a zoom lens having a four-group configuration without increasing the power ratio of the first group to the second group, ensuring a variable power ratio, and reducing the size. It is to plan.

Another specific problem of the present invention is that a zoom lens suitable for a digital camera or the like realizes a light beam nearly telecentric in consideration of an image pickup device such as a CCD, and a low-pass filter and a light beam. It is an object of the present invention to secure a back focus so that a dividing element and the like can be arranged as necessary, secure an excellent imaging performance, and realize a small zoom lens with a small number of components.

[0008]

To achieve the above object, a zoom lens according to the present invention comprises, in order from the object side, a first group fixed at the time of zooming having a positive refractive power, and a zoom lens having a negative refractive power. When moving from the object side to the image plane side from the wide-angle end to the telephoto end,
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. Is satisfied. _{0.5 <| F 2 / F 3} | <1.2 ··· (1) where, F _i is the focal length of the i group.

Another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and fixed during zooming,
A second lens unit having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end when zooming, and an object having a positive refractive power and moving from the image plane side to the telephoto end when zooming A third lens unit that moves to the side, and a fourth lens unit that has a positive refractive power and is movable at the time of zooming, and satisfies the following conditional expression. 0.49 <| L ₃ / L ₂ | <1 (2) Here, _Li is the amount of movement of the i-th lens unit from the wide-angle end to the telephoto end.

Still another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power from the wide-angle end to the telephoto end at zooming. A second lens unit that moves from the object side to the image plane side, and a third lens unit that has positive refractive power and moves from the image plane side to the object side from the wide angle end to the telephoto end when zooming. It has a fourth group movable at the time, and satisfies the following conditional expression. 2 <(F _3,4W ) / IH <3.3 (3) where (F _3,4W ) is the combined focal length of the third and fourth _units at the wide-angle end, and IH is the radius of the image circle. It is.

Still another zoom lens system according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and a negative lens unit having a negative refractive power from the object side to the image plane side from the wide-angle end to the telephoto end during zooming. A third group having a positive refractive power, a fourth group having a positive refractive power and movable during zooming, and the third group has a convex surface on the object side in order from the object side. Positive lens,
The third lens unit comprises a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image surface side. The positive lens and the cemented lens on the object side in the third group are both around the convex surface facing the object side. The part is held in a state of being applied to the lens frame part on the periphery or at several places thereof.

Hereinafter, the reason why the above configuration is employed in the present invention and the operation thereof will be described. In recent years, in the field of cameras using electronic imaging means such as camcorders and digital cameras, there has been an increasing demand for small and low-cost zoom lenses for consumer use. Japanese Patent Application Laid-Open No. 6-194997 and JP-A-6-194 mentioned above can meet such a demand.
No. 572. As described above, these have a zoom ratio of about 8 to 12, and most of the zooming action is carried by the second lens unit. In this case, in order to keep the image point substantially constant, the lateral magnification of the second lens unit must be in the range of about -1 from the wide-angle end to the telephoto end.

However, in order to further reduce the zoom ratio by making the zoom ratio smaller than this, the amount of movement of the second lens group can be small. It is efficient that the space between groups is tightly packed for miniaturization.

However, in order for the second unit to change the magnification by taking a lateral magnification of about -1 in a state where the distance between the first unit and the second unit is reduced, the power of the first unit with respect to the second unit must be increased. Must. As a result, the entrance pupil becomes farther, the height of off-axis rays passing through the first group increases, and the lens system of the first group increases in size. Accordingly, the thickness of the lenses of the first group also increases. Further, since the curvature of each lens of the first group must be increased, the thickness of the first group lens also increases in order to secure the edge (edge) of the lens.

On the other hand, in the present invention, these problems are avoided by increasing the ratio of the load of the zooming action of the third lens unit, and the power ratio of the first lens unit and the second lens unit is not changed so much. The zoom ratio is secured and the size is reduced. At this time,
In order for the third lens unit to have a large zooming effect, the third lens unit must have relatively large power, and conditional expression (1) defines this. Here, if the power of the third lens group becomes weaker than the power of the second lens group by exceeding the lower limit of 0.5 of the expression (1), the moving distance of the third lens group during zooming becomes too large. Along with this, the amount of movement of the second lens unit for keeping the image plane position constant also increases, which hinders miniaturization. If the power of the third lens unit with respect to the second lens unit is increased beyond the upper limit of 1.2, the amount of astigmatism generated in the third lens unit becomes too large, and the object points of the third lens unit and the third lens unit are increased. Is too short, so that a sufficient distance cannot be obtained between the second group and the third group, which is not preferable. It is more desirable to satisfy the following conditional expression.

0.6 <| F ₂ / F ₃ | <1 (4) In the present invention, since the third lens unit has a relatively large zooming action as described above, the third lens unit It is necessary to increase the amount of movement during zooming. Conditional expression (2) relates to this, and defines the ratio of the amount of movement of the second and third units from the wide-angle end to the telephoto end. If the lower limit of conditional expression (2), 0.49, is exceeded and the amount of movement of the third lens unit with respect to the second lens unit is small, it is not preferable because the third lens unit cannot have a sufficient zooming effect. If the amount of movement of the third lens group with respect to the second lens group becomes larger than the upper limit of 1, the third lens group becomes larger.
Aberration fluctuations such as astigmatism and coma aberration during zooming of the group become too large, and the distance between the third group and the object point of the third group at the telephoto end becomes too short. The interval between the three groups cannot be sufficiently secured, which is not preferable.

In addition, the positive, negative, positive, positive
In the case of group zoom, the power of the third and fourth groups that relays the virtual image of the first and second groups to the imaging surface is increased, and the position of the virtual image of the first and second groups and the position of the imaging surface are compared. Since shortening the distance is effective for shortening the overall length of the lens system, the configuration is such that the combined power of the third and fourth units is increased. The conditional expression (3) relates to this, and the conditional expression (3)
When the combined focal length at the wide-angle end of the third lens unit and the fourth lens unit exceeds the upper limit of 3.3 and becomes larger (power becomes weaker) with respect to the image circle radius (image height) IH, The miniaturization is not sufficient. Also, the lower limit of conditional expression (3), 2
When the combined focal length at the wide-angle end of the third unit and the fourth unit is smaller than the radius of the image circle (power becomes stronger), the astigmatism generated in the third unit and the fourth unit increases. At the same time, the distance between the third lens unit and the object point of the third lens unit becomes too short, and the distance between the second lens unit and the third lens unit at the telephoto end cannot be sufficiently obtained.

In the case of a zoom lens according to the present invention, it is preferable that focusing is performed by the fourth lens unit having a relatively small incident angle of the axial light beam, because aberration variation during focusing is small. In addition, since the fourth lens group has a relatively small lens diameter and is lightweight, there is an advantage that the driving torque at the time of focusing may be small.

It is advantageous to make the third lens unit as much as possible out of the combined power of the third and fourth lens units in order to reduce the overall length of the lens. Therefore, in the present invention, the third lens unit has a relatively large power with respect to the fourth lens unit. The following conditional expression (5) relates to this, and defines the ratio of the focal length of the third lens unit to the focal length of the fourth lens unit.

0.3 <F ₃ / F ₄ <0.8 (5) where F _i is the focal length of the i-th lens unit. Conditional expression (5)
By making the ratio of the focal length of the third lens group to the focal length of the fourth lens group smaller than the upper limit of 0.8, it is possible to further reduce the size as compared with the related art. If the ratio of the focal length of the third lens unit to the focal length of the fourth lens unit is smaller than the lower limit of 0.3 of the conditional expression (5), the power of the fourth lens unit becomes too weak, and focusing is performed by the fourth lens unit. In this case, the amount of focusing movement becomes too large, and the fluctuation of aberration due to focusing becomes large, which is not preferable.

Further, in the present invention, as described above, since the fourth unit has a relatively smaller power than the third unit, the fourth unit is composed of one positive lens in order to reduce the size of the lens system. Is desirable. In order to suppress fluctuation of astigmatism due to zooming, it is desirable that at least one surface of the fourth unit is an aspheric surface.

In the present invention, it is desirable to satisfy the following conditional expression (6). 0.4 <| β _2T | <1 (6) Here, β _2T is the lateral magnification of the second unit at the telephoto end.

Equation (6) defines the absolute value of the lateral magnification at the telephoto end of the second lens unit.
If the absolute value of the lateral magnification at the telephoto end of the group is small, the zooming effect of the second group is not sufficient, and the power of the first group is too weak, so that the lens cannot be downsized. If the absolute value of the lateral magnification at the telephoto end of the second lens unit is increased beyond the upper limit of 1, the zooming action of the third lens unit will not be sufficient, and the power of the first lens unit will be too strong. The lens system of the group becomes large and hinders miniaturization.

It is preferable that the third lens unit should have a high power without changing the imaging magnification of the third lens unit, thereby contributing to downsizing of the entire lens system. At this time, in order to avoid interference between the second and third groups at the telephoto end due to the short distance between the third group and the object point of the third group, the principal point of the third group is set as close to the object side as possible. It is desirable to put. For this reason, it is desirable that the third unit is composed of three positive, positive and negative lenses in order from the object side, and at least one surface is made aspherical in order to correct spherical aberration.

Further, by making at least one surface in the second lens unit an aspherical surface, fluctuations in astigmatism and coma due to zooming can be corrected more favorably. In the present invention, since the third unit bears a relatively large zooming effect as described above, the burden of aberration correction on the first and second units can be reduced. It can be composed of one lens. At this time, in order to correct the chromatic aberration of magnification occurring in the first group, it is desirable that the most object side of the second group is constituted by a negative lens having a relatively large dispersion. (7) below
The equation relates to this and defines the Abbe number of the negative lens closest to the object side in the second group. ν ₂₁ <40 (7) Here, ν ₂₁ is the Abbe number of the negative lens closest to the object side in the second group.

As described above, in order to correct the chromatic aberration of magnification occurring in the positive lens of the first group, the Abbe number of the negative lens closest to the object in the second group is set to the upper limit of 40 in the equation (7). It is desirable not to exceed. Further, when the following conditional expression (8) is satisfied, lateral chromatic aberration can be corrected more favorably.

Ν ₂₁ <35 (8) Further, as in the present invention, the third lens unit is arranged in the order of positive, positive,
In the case of a configuration including three negative lenses, the principal point of the entire third unit is placed as close to the object side as possible for miniaturization, so that the two positive lenses both have a convex surface facing the object side and the negative lens faces the image side. It is desirable to have a shape that faces a concave surface which is strong to the surface. In such a configuration, the convex surface facing the object side of the two positive lenses having strong refractive power and the concave surface facing the image surface side of the negative lens have an eccentricity error with respect to the optical axis at the time of manufacture. The effect on performance degradation is likely to increase. For this reason, the positive lens and the negative lens on the image plane side are cemented lenses, and when held by the lens holding frame, both the positive lens and the cemented lens on the object side surround the periphery of the convex surface facing the object side or several places on the periphery. It is desirable that the sheet is held in a state where it is applied to the holding frame.

Further, another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and fixed during zooming,
A second lens unit having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end when zooming, and an object having a positive refractive power and moving from the image plane side to the telephoto end when zooming A third lens unit that always moves to the side, a fourth lens unit that has a positive refractive power and is movable at the time of zooming, and the third lens unit includes a cemented lens including a positive lens and a negative lens, and the fourth lens unit Can be configured to include one positive lens.

With this configuration, at the time of zooming, the second unit having negative refractive power is moved from the object side to the image plane side from the wide-angle end to the telephoto end, and the third unit having positive refractive power is moved. By moving from the image plane side to the object side, the burden of zooming, which was conventionally borne by the second group, can be divided into the second group and the third group. Accordingly, it is possible to secure a variable power ratio and reduce the size without increasing the ratio of the power of the first unit to the second unit. That is, with such a configuration, by increasing the ratio of the burden of the zooming action of the third group, the zooming ratio is secured without increasing the power ratio between the first and second groups, and the size is reduced. Can be achieved.

Next, the function and effect of the third group having a cemented lens composed of a positive lens and a negative lens will be described. Since the third group is a movable group during zooming, the burden of aberration correction of the third group with respect to aberration fluctuation during zooming is increased, and it is necessary to satisfactorily correct chromatic aberration. For this reason, the third unit requires at least a positive lens component and a negative lens component. At this time, if relative eccentricity occurs between the positive lens and the negative lens, the imaging performance is greatly deteriorated. In the above configuration,
By employing a cemented lens composed of a positive lens and a negative lens in the third group, the eccentricity between the positive lens and the negative lens can be easily reduced. That is, it was possible to increase the ratio of the burden of the zooming action of the third lens unit, satisfactorily correct the chromatic aberration, and make it difficult for the image quality to deteriorate due to eccentricity. Further, in the above configuration, the burden of zooming, which was conventionally borne by the second lens group, is divided into the second lens group and the third lens group. This also succeeds in reducing the aberration correction burden on the fourth lens group. By forming the fourth group with one positive lens, it is possible to achieve imaging performance and downsizing.

In the above configuration, it is desirable that at least one surface of the fourth group positive lens is an aspheric surface.

When the fourth unit is composed of one positive lens, since the fourth unit has one aspherical surface, the burden of zooming is divided into the second and third units, and the load is reduced. It is possible to perform aberration correction borne by the fourth lens group more favorably, and achieve low cost and downsizing. The aspherical surface may be formed by a so-called glass press, a method of arranging a thin resin layer on a base material such as glass (a so-called hybrid type), or a method of molding a plastic.

Further, another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and a negative lens having a negative refractive power and a wide-angle end to a telephoto end at zooming. A second lens unit that moves from the object side to the image surface side during the zooming, a third lens unit that has a positive refractive power and always moves from the image surface side to the object side from the wide angle end to the telephoto end during zooming, and has a positive refractive power The zoom lens may further include a fourth lens unit that is movable at the time of zooming, and the second and third units may each include a cemented lens including a positive lens and a negative lens.

With this configuration, the second lens unit having a negative refractive power is moved from the object side to the image surface side from the wide-angle end to the telephoto end during zooming, and the third lens unit having a positive refractive power is moved to the image side. By moving from the surface side to the object side, the burden of zooming, which was conventionally borne by the second group, can be divided into the second group and the third group. Accordingly, it is possible to secure a variable power ratio and reduce the size without increasing the ratio of the power of the first unit to the second unit. That is, in this configuration, by increasing the ratio of the burden of the zooming action of the third lens unit, the zooming ratio is secured without increasing the power ratio between the first lens unit and the second lens unit, and miniaturization is achieved. be able to.

Next, the function and effect of the third group having a cemented lens composed of a positive lens and a negative lens will be described. Since the third group is a movable group during zooming, the burden of aberration correction of the third group with respect to aberration fluctuation during zooming is increased, and it is necessary to satisfactorily correct chromatic aberration. For this reason, the third unit requires at least a positive lens component and a negative lens component. At this time, if relative eccentricity occurs between the positive lens and the negative lens, the imaging performance is greatly deteriorated. In the above configuration,
By employing a cemented lens composed of a positive lens and a negative lens in the third group, the eccentricity between the positive lens and the negative lens can be easily reduced. That is, it was possible to increase the ratio of the burden of the zooming action of the third lens unit, satisfactorily correct the chromatic aberration, and make it difficult for the image quality to deteriorate due to eccentricity. Although the second group also has a lighter load, it is also a movable group at the time of zooming, and the second group has a large burden of aberration correction for aberration fluctuations during zooming, and it is necessary to satisfactorily correct chromatic aberration. Therefore, the second group requires at least a positive lens component and a negative lens component. At this time, if relative eccentricity occurs between the positive lens and the negative lens, the imaging performance is greatly deteriorated. In the above configuration, the eccentricity between the positive lens and the negative lens can be easily reduced by employing the cemented lens including the positive lens and the negative lens in the second group. In other words, it was possible to achieve a reduction in image quality deterioration due to eccentricity.

Another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and a negative lens having a negative refractive power and a wide-angle end to a telephoto end at zooming. A second lens unit that moves from the object side to the image surface side during the zooming, a third lens unit that has a positive refractive power and always moves from the image surface side to the object side from the wide angle end to the telephoto end during zooming, and has a positive refractive power The zoom lens further includes a fourth unit movable at the time of zooming, wherein the third unit includes a positive lens from the object side and a cemented lens including a positive lens and a negative lens. it can.

With this arrangement, the second unit having negative refractive power is moved from the object side to the image plane side from the wide-angle end to the telephoto end during zooming, and the third unit having positive refractive power is moved to the image side. By moving from the surface side to the object side, the burden of zooming, which was conventionally borne by the second group, can be divided into the second group and the third group. Accordingly, it is possible to secure a variable power ratio and reduce the size without increasing the ratio of the power of the first unit to the second unit. That is, in this configuration, by increasing the ratio of the burden of the zooming action of the third lens unit, the zooming ratio is secured without increasing the power ratio between the first lens unit and the second lens unit, and miniaturization is achieved. be able to. In addition, since the third lens unit is composed of three positive, positive, and negative lenses in order from the object side, the principal points of the entire third lens unit can be arranged on the object side, thereby achieving further miniaturization. In other words, the negative lens is necessary for chromatic aberration correction, and achieves stronger positive power than the arrangement of two positive lenses and downsizing of the third unit itself (simple configuration). Further, the third lens group is arranged in order from the object side,
By arranging positive and negative positions, various aberrations are satisfactorily corrected with a small number of lenses, and the principal points of the entire third group are arranged on the object side, and the principal points of the second and third groups at the telephoto end. The position can be approached efficiently, and further miniaturization of the whole system has been achieved.

Further, another zoom lens according to the present invention comprises, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, The zoom lens has a fourth lens unit having a positive refractive power.
The distance between the groups, the distance between the second and third groups, and the distance between the third and fourth groups change respectively, and the third group is, in order from the object side,
The fourth group includes a biconvex positive lens, a cemented lens of a positive meniscus lens having a convex surface facing the object side, and a cemented lens of a negative meniscus lens, and the fourth group includes a biconvex lens having a large curvature on the object side surface. be able to.

In this configuration, the third lens unit includes, in order from the object side, a positive lens having a convex surface facing the object side, and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens. The main point of the entire third lens unit can be placed closer to the object side, and the size of the lens system can be reduced. Further, by using a positive meniscus lens and a negative meniscus lens as cemented lenses, performance deterioration due to eccentricity is suppressed. With the third group having such a configuration, the fourth group can be configured with one single lens,
Further, by making the single lens a biconvex lens having a large curvature on the object side, light rays incident on the image plane can be made close to telecentric while minimizing the number of lenses in the third and fourth groups, and the back focus can be improved. And the above-mentioned another problem is solved.

Further, another zoom lens according to the present invention comprises, in order from the object side, a first group having a positive refractive power, a second group having a negative refractive power, a third group having a positive refractive power, The zoom lens has a fourth lens unit having a positive refractive power.
The distance between the groups, the distance between the second and third groups, and the distance between the third and fourth groups change respectively, the first group is composed of one positive lens, and the second group is located on the object side. And three lenses, a single lens and a cemented lens of a negative lens and a positive lens, are arranged in this order. The third group includes, in order from the object side, a single lens and a cemented lens of a positive lens and a negative lens. Three lenses may be arranged, and the fourth group may include one positive lens.

With this configuration, it is possible to achieve a positive / negative / positive / positive zoom lens suitable for a digital camera capable of obtaining good imaging performance with a small number of components. In other words, a configuration in which the burden of aberration correction is concentrated on the second group and the third group is adopted, and the first group and the fourth group with small burden of aberration correction can each be configured with one positive lens. The configuration of the second group, which has a large burden of aberration correction, is changed to a single lens, and a cemented lens of a negative lens and a positive lens in order from the object side. Various aberrations can be reduced, which can contribute to further miniaturization. Further, the negative lens and the positive lens of the second group are cemented lenses to suppress performance deterioration due to eccentricity. The configuration of the third group, which has a large burden of aberration correction, is made up of a single lens and a cemented lens of a positive lens and a negative lens in order from the object side. Aberrations can be reduced, which can contribute to further miniaturization. Further, the third lens unit has a positive lens and a negative lens as cemented lenses to suppress performance deterioration due to eccentricity.

By reducing the power of the first lens unit, the amount of aberration generated in the first lens unit can be reduced.
It is desirable that the load of aberration correction generated in the first group in the second group and the third group is reduced. It is desirable that the following conditional expression is satisfied.

8 <F ₁ / IH <20 (9) where F ₁ is the focal length of the first lens unit, and IH is the image height (the length from the center of the image to the outermost periphery of the image. Image circle radius Same as.) When the lower limit of 8 to condition (9) is exceeded,
The amount of occurrence of aberration in the first group increases, which is not preferable.
If the upper limit of 20 is exceeded, the power of the first lens unit becomes weak, and a sufficient zoom ratio cannot be secured, or downsizing cannot be achieved.

Further, another zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, The zoom lens has a fourth lens unit having a positive refractive power.
The distance between the groups, the distance between the second and third groups, and the distance between the third and fourth groups change respectively, and the first group is composed of two lenses, a positive lens and a negative lens. The third group may be configured to include at least one cemented lens of a positive lens and a negative lens.

In this configuration, the first group is composed of two lenses, a positive lens and a negative lens, so that the chromatic aberration generated in the first group can be reduced regardless of the power of the first group. Can be reduced, and as a result, the entire optical system can be downsized. On this occasion,
By having a cemented lens of a positive lens and a negative lens in the second or third group, it is possible to reduce chromatic aberration that occurs in other than the first group, and to prevent deterioration of imaging performance due to eccentricity or the like. As a result, an optical system that is advantageous in terms of the number of components, manufacturing cost, and size reduction can be achieved.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 10 of the zoom lens according to the present invention will be described below. 1 to 10 are sectional views showing the lens arrangement at the wide-angle end of the zoom lenses of Examples 1 to 10, respectively. Numerical data of each embodiment will be described later.

In the first embodiment, the focal length is between 5.50 and 15.7.
5. A zoom lens with an angle of view of 66.42 ° to 24 °,
As shown in FIG. 1, the first group G1 includes a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens,
The second group G2 includes a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave lens and a biconvex lens,
Thereafter, the stop S is located, and the third unit G3 is a biconvex lens 2
The fourth group G4 includes one positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. An aspherical surface is used for the most object side surface of the third lens unit G3. At the time of zooming from the wide-angle end to the telephoto end, the first unit G1 and the stop S are fixed, the second unit G2 moves from the object side to the image plane side, and the third unit G
The third and fourth units G4 move from the image plane side to the object side while widening the mutual distance.

The second embodiment has a focal length of 5.52 to 15.9.
1. A zoom lens having an angle of view of 67.04 ° to 23.72 °. As shown in FIG. 2, the first group G1 is a cemented lens of a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens. The second group G2 is composed of a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. Consists of two biconvex lenses and a negative meniscus lens having a convex surface facing the object side.
Reference numeral 4 includes one biconvex lens. An aspherical surface is used for the most object side surface of the third lens unit G3. At the time of zooming from the wide-angle end to the telephoto end, as shown by the arrow in the figure, the first unit G1 and the stop S are fixed, and the second unit G2 moves from the object side to the image plane side.
The third lens unit G3 and the fourth lens unit G4 move from the image plane side to the object side while increasing the mutual distance.

The third embodiment has a focal length of 5.50 to 15.8.
1. A zoom lens having an angle of view of 66.82 ° to 23.88 °. As shown in FIG. 3, the first group G1 includes a cemented lens of a negative meniscus lens having a convex surface facing the object side and a biconvex lens. The second group G2 is composed of a biconcave lens and a positive lens, and thereafter the stop S is located. The third group G3 is a biconvex lens, a positive meniscus lens having a convex surface facing the object side, and a The fourth group G4 includes one positive meniscus lens having a convex surface facing the object side. The most image-side surface of the second group G2;
Aspheric surfaces are used for the most object side surface of the third group G3 and the most object side surface of the fourth group G4. At the time of zooming from the wide-angle end to the telephoto end, as shown by the arrow in the figure, the first unit G1 and the stop S are fixed, and the second unit G2 moves from the object side to the image plane side.
The third lens unit G3 and the fourth lens unit G4 move from the image plane side to the object side while increasing the mutual distance.

The fourth embodiment has a focal length of 5.50 to 15.8.
7, a zoom lens having an angle of view of 64.93 ° to 24.87 °. As shown in FIG. 4, the first group G1 includes one positive meniscus lens having a convex surface facing the object side, and the second group. G2
Is composed of a negative meniscus lens having a convex surface facing the object side, a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side, and then the stop S is located. The third group G3 is a biconvex lens. And a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens, and the fourth group G4 comprises one biconvex lens. Third group G
Aspherical surfaces are used for the most object-side surface of No. 3 and the most object-side surface of the fourth lens unit G4. At the time of zooming from the wide-angle end to the telephoto end, the first unit G1 and the stop S are fixed, the second unit G2 moves from the object side to the image plane side, and the third unit G
The third and fourth units G4 move from the image plane side to the object side while widening the mutual distance.

The fifth embodiment has a focal length of 5.50 to 15.8.
6. A zoom lens having an angle of view of 68.30 ° to 24.54 °. As shown in FIG. 5, the first group G1 includes a negative meniscus lens having a convex surface facing the object side, and a convex surface having a convex surface facing the object side. The second group G2 is composed of a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side. The third group G3 includes a biconvex lens, and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The fourth group G4 has a biconvex lens 1 Consists of sheets.
Aspheric surfaces are used for the surface closest to the image plane in the second group G2, the surface closest to the object in the third group G3, and the surface closest to the object in the fourth group G4. At the time of zooming from the wide-angle end to the telephoto end, the first group G1 and the stop S are fixed and the second group G
2 moves from the object side to the image plane side, and the third group G3 and the fourth group G
4 moves from the image plane side to the object side while widening the mutual distance.

[0052] In the fifth embodiment, as shown in FIG. 11, on the periphery of the convex cemented lens L ₃₂ and the positive lens L ₃₁ on the object side of the third group G3 that both toward the object side peripheral or It is held in a state where it is applied to the holding frame 1 at several places, so that an eccentric error which easily affects performance is reduced.

In the sixth embodiment, the focal length is 6.608 to 19.
098, an angle of view of 67.32 ° to 25.95 °. As shown in FIG. 6, the first group G1 includes one convex and plano lens, and the second group G2 has a convex surface on the object side. , A cemented lens of a bi-concave lens and a positive meniscus lens having a convex surface facing the object side, followed by a stop S. The third group G3 includes a bi-convex lens and a convex surface facing the object side. The fourth group G4 includes one biconvex lens. The positive lens has a cemented positive meniscus lens and the negative meniscus lens has a convex surface facing the object side. Aspheric surfaces are used for the most object side surface of the third group G3 and the most object side surface of the fourth group G4. At the time of zooming from the wide-angle end to the telephoto end, the first group G1 and the aperture S are fixed, the second group G2 moves from the object side to the image plane side, and the third group G3 And the fourth unit G4 move from the image plane side to the object side while widening the mutual distance.

In the seventh embodiment, the focal lengths are 6.613 to 18.13.
999, an angle of view of 67.68 ° to 26.08 °. As shown in FIG. 7, the first group G1 includes one convex and plano lens, and the second group G2 has a convex surface on the object side. , A cemented lens of a bi-concave lens and a positive meniscus lens having a convex surface facing the object side, followed by a stop S. The third group G3 includes a bi-convex lens and a convex surface facing the object side. The fourth group G4 includes a bi-convex lens and a negative meniscus lens having a convex surface facing the image surface side. The fourth lens unit G4 includes a cemented lens of a positive meniscus lens having a positive surface and a negative meniscus lens having a convex surface facing the object side. An aspherical surface is used for the most object side surface of the third lens unit G3. At the time of zooming from the wide-angle end to the telephoto end, the first group G1 and the aperture S are fixed, the second group G2 moves from the object side to the image plane side, and the third group G3 And the fourth unit G4 move from the image plane side to the object side while widening the mutual distance.

In the eighth embodiment, the focal length is 6.548-19,
A zoom lens having an angle of view of 67.80 ° to 26.08 °. As shown in FIG. 8, the first group G1 has a negative meniscus lens having a convex surface facing the object side and a convex surface having a convex surface facing the object side. The second group G2 is composed of a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side. The third group G3 includes a biconvex lens and a cemented lens of a biconvex lens and a biconcave lens, and the fourth group G4 includes a single biconvex lens. Third group G
Aspherical surfaces are used for the most object-side surface of No. 3 and the most object-side surface of the fourth lens unit G4. At the time of zooming from the wide-angle end to the telephoto end, the first unit G1 and the stop S are fixed, the second unit G2 moves from the object side to the image plane side, and the third unit G
The third and fourth units G4 move from the image plane side to the object side while widening the mutual distance.

The ninth embodiment has a focal length of 6.562-19,
A zoom lens having an angle of view of 67.69 ° to 26.08 °. As shown in FIG. 9, the first group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second group G2 is composed of a cemented lens of a meniscus lens.
Is composed of a negative meniscus lens having a convex surface facing the object side, a cemented lens of a biconcave lens and a positive meniscus lens having a convex surface facing the object side, and then the stop S is located. The third group G3 is a biconvex lens. And the fourth lens unit G4 includes a single biconvex lens. Aspheric surfaces are used for the most object side surface of the third group G3 and the most object side surface of the fourth group G4. At the time of zooming from the wide-angle end to the telephoto end, the first group G1 and the aperture S are fixed, the second group G2 moves from the object side to the image plane side, and the third group G3 And the fourth unit G4 move from the image plane side to the object side while widening the mutual distance.

The tenth embodiment has a focal length of 6.46 to 19,
A zoom lens having an angle of view of 68.52 ° to 26.08 °. As shown in FIG. 10, the first group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus having a convex surface facing the object side. The second group G2 includes a cemented lens of lenses and a positive meniscus lens having a convex surface facing the object side. The second group G2 includes a negative meniscus lens having a convex surface facing the object side, and a biconcave lens and a positive meniscus lens having a convex surface facing the object side. The third group G3 is composed of a biconvex lens and a cemented lens of a biconvex lens and a biconcave lens, and the fourth group G4 is composed of one biconvex lens. Aspheric surfaces are used for the most object side surface of the third group G3 and the most object side surface of the fourth group G4. At the time of zooming from the wide-angle end to the telephoto end, the first group G1 and the aperture S are fixed, the second group G2 moves from the object side to the image plane side, and the third group G3 And the fourth unit G4 move from the image plane side to the object side while widening the mutual distance.

In the following, numerical data of the above embodiments are shown. Symbols other than those described above, f is the focal length of the entire system, F _NO is the F number, r ₁ , r ₂ ... Are the radii of curvature of the lens surfaces, d ₁ , d
₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, ν _d1, ν _d2 ... is the Abbe number of d line of each lens. The aspherical shape is represented by the following equation, where x is an optical axis where the traveling direction of light is positive, and y is a direction perpendicular to the optical axis. ^{x = (y 2 / r)} / [1+ {1- (K + 1) (y / r)
_{^{2} 1/2] + A 4 y}} 4 + A 6 y 6 + A 8 y 8 + A 10 y 10 + A 12
y ¹² where r is the paraxial radius of curvature, K is the conic coefficient, A ₄ , A ₆ ,
A ₈ , A ₁₀ , and A ₁₂ are the fourth, sixth, eighth, tenth,
It is a twelfth order aspheric coefficient.

[0059] Example 1 f = 5.505 ~ 9.536 ~ 15.745 F NO = 2.792 ~ 3.216 ~ 4.113 r 1 = 186.5411 d 1 = 1.2000 n d1 = 1.84666 ν d1 = 23.78 r 2 = 39.3312 d 2 = 3.9807 n d2 = 1.48749 ν _{d2 = 70.23 r 3 = -56.8902 d} 3 = 0.1800 r 4 = 14.7260 d 4 = 3.2694 n d3 = 1.69680 ν d3 = 55.53 r 5 = 62.1210 d 5 = ( _{variable) r 6 = 74.5065 d 6 =} 0.8400 n d4 = 1.77250 _{ν d4 = 49.60 r 7 = 5.5423} d 7 = 2.9761 r 8 = -9.7293 d 8 = 0.8400 n d5 = 1.48749 ν d5 = 70.21 r 9 = 11.8229 d 9 = 1.8000 n d6 = 1.84666 ν d6 = 23.78 r 10 = -139.7255 d ₁₀ = (variable) r ₁₁ = ∞ (aperture) d ₁₁ = (variable) r ₁₂ = 11.6742 (aspherical surface) d ₁₂ = 1.9422 n _d7 = 1.58913 ν _d7 = 61.18 r ₁₃ = -23.0900 d ₁₃ = 0.1500 r _{14 = 8.6783 d 14 = 2.6167 n d8} = 1.72916 ν d8 = 54.68 r 15 = -12.4135 d 15 = 0.3000 r 16 = 26.9742 d 16 = 0.7000 n d9 = 1.84666 ν d9 = 23.78 r 17 = 4.2272 d 17 = ( variable) r _{18 = 9.6808 d 18 = 1.6130 n} d10 = 1 .72916 ν _d10 = 54.68 r ₁₉ = 32.9326 Aspherical coefficients twelfth surface _{K = -0.2184 A 4 = -9.0556 ×} 10 -4 A 6 = -2.5457 × 10 -5 A 8 = 1.4387 × 10 -6 A 10 = -9.7103 × 10 -8 | F 2 / F ₃ | = 0.714 F ₃ / F ₄ = 0.539 | β _2T | = 0.797 | L ₃ / L ₂ | = 0.73 (F _3,4W ) _/IH=2.44 F _{1 /IH=6.97}
.

[0060] Example 2 f = 5.524 ~ 9.537 ~ 15.914 F NO = 2.784 ~ 3.389 ~ 4.215 r 1 = 18.1384 d 1 = 1.2000 n d1 = 1.84666 ν d1 = 23.78 r 2 = 12.8515 d 2 = 5.1730 n d2 = 1.60311 ν _{d2 = 60.64 r 3 = 229.0224 d} 3 = ( _{variable) r 4 = 41.3044 d 4 =} 0.7827 n d3 = 1.65160 ν d3 = 58.55 r 5 = 5.1749 d 5 = 3.5350 r 6 = -33.2963 d 6 = 0.7000 n d4 = 1.56384 _{ν d4 = 60.67 r 7 = 20.7633} d 7 = -0.0132 r 8 = 8.2198 d 8 = 1.7596 n d5 = 1.80518 ν d5 = 25.42 r 9 = 13.1948 d 9 = ( variable) r ₁₀ = ∞ (stop) d ₁₀ = ( Variable) r ₁₁ = 12.3402 (aspherical surface) d ₁₁ = 3.6983 n _d6 = 1.67790 v _d6 = 55.34 r ₁₂ = -11.8524 d ₁₂ = 0.8580 r ₁₃ = 11.4834 d ₁₃ = 2.3550 n _d7 = 1.60311 v _d7 = 60.64 r ₁₄ = _{-18.6404 d 14 = 0.1297 r 15 =} 48.4996 d 15 = 0.7000 n d8 = 1.84666 ν d8 = 23.78 r 16 = 5.5496 d 16 = ( _{variable) r 17 = 14.2502 d 17 =} 1.7219 n d9 = 1.58913 ν d9 = 61.14 r 18 = -86.9086 Aspheric surface eleventh surface K = -0.2184 A ₄ = -7.1086 × 10 ^-4 A ₆ = 2.9893 × 10 ^-5 A ₈ = -3.3152 × 10 ^-6 A ₁₀ = 1.3762 × 10 ^-7 | F ₂ / F ₃ | = 0.737 F ₃ / F ₄ = 0.475 | β _2T | = 0.501 | L ₃ / L ₂ | = 0.62 (F _3,4W ) _/IH=2.58 F _{1 /IH=10.99}
.

[0061] Example 3 f = 5.505 ~ 9.528 ~ 15.810 F NO = 2.786 ~ 3.348 ~ 4.330 r 1 = 19.0896 d 1 = 1.2000 n d1 = 1.84666 ν d1 = 23.78 r 2 = 14.7521 d 2 = 3.0968 n d2 = 1.60311 ν _{d2 = 60.64 r 3 = -7692.3867 d} 3 = ( _{variable) r 4 = -76.4386 d 4 =} 0.8400 n d3 = 1.77250 ν d3 = 49.60 r 5 = 4.8598 d 5 = 1.8112 r 6 = 18.2814 d 6 = 1.7596 n d4 = 1.80518 ν _d4 = 25.42 r ₇ = ∞ (aspherical surface) d ₇ = (variable) r ₈ = ∞ (aperture) d ₈ = (variable) r ₉ = 7.3400 (aspherical surface) d ₉ = 2.6421 n _d5 = 1.58913 ν _{d5 = 61.18 r 10 = -22.1205 d 10} = 0.1500 r 11 = 8.0241 d 11 = 1.9734 n d6 = 1.72916 ν d6 = 54.68 r 12 = 52.4926 d 12 = 0.1500 r 13 = 14.0423 d 13 = 0.7000 n d7 = 1.84666 ν d7 = 23.78 r ₁₄ = 4.0797 d ₁₄ = (variable) r ₁₅ = 10.1820 (aspherical surface) d ₁₅ = 1.7446 n _d8 = 1.58913 ν _d8 = 61.14 r ₁₆ = 1133.0330 Aspheric surface 7th surface K = 0 A ₄ = -5.8146 × 10 ^-4 A ₆ = -3.5256 × 10 ^-7 A ₈ = -1.1100 × 10 ^-6 A ₁₀ = 9.7216 × 10 ^-9 9th surface K =- ^{_{0.2184 A 4 = -5.1506 × 10 -4}} A 6 = -2.2707 × 10 -6 A 8 = 2.5686 × 10 -7 A 10 = -1.0482 × 10 -8 15th surface _{K = 0 A 4 = -2.2630 ×} 10 - ⁴ A ₆ = 1.7763 × 10 ^-5 A ₈ = -1.5096 × 10 ^-6 A ₁₀ = 9.3766 × 10 ^-8 | F ₂ / F ₃ | = 0.866F ₃ / F ₄ = 0.591 | β _2T | = 0.575 | L _{3 / L 2 | = 0.68 (} F 3,4W) / IH = 2.52 F 1 / IH = 10.06
.

[0062] Example 4 f = 5.502 ~ 9.509 ~ 15.873 F NO = 2.777 ~ 3.341 ~ 4.352 r 1 = 16.5657 d 1 = 3.6105 n d1 = 1.48749 ν d1 = 70.23 r 2 = 570.4842 d 2 = ( Variable) r ₃ = _{33.8910 d 3 = 0.8356 n d2 =} 1.84666 ν d2 = 23.78 r 4 = 5.4863 d 4 = 2.6452 r 5 = -13.8594 d 5 = 0.8000 n d3 = 1.48749 ν d3 = 70.23 r 6 = 7.7346 d 6 = 2.6020 n d4 = 1.84666 _{ν d4 = 23.78 r 7 = 423.2622} d 7 = ( variable) r ₈ = ∞ (stop) d ₈ = (variable) r ₉ = 8.6181 _{(aspherical) d 9 = 3.3470 n d5 =} 1.56384 ν d5 = 60.67 r 10 = _{-16.8991 d 10 = 0.1208 r 11 =} 7.7569 d 11 = 2.8653 n d6 = 1.77250 ν d6 = 49.60 r 12 = 258.5476 d 12 = 0.7000 n d7 = 1.84666 ν d7 = 23.78 r 13 = 4.5291 d 13 = ( variable) r ₁₄ = 9.7155 _{(aspherical) d 14 = 2.4486 n d8 =} 1.56384 ν d8 = 60.67 r 15 = -47.1886 Aspheric surface ninth surface K = -0.2184 A ₄ = -3.1865 × 10 ^-4 A ₆ = 2.3167 × 10 ^-7 A ₈ = 1.3223 × 10 ^-8 A ₁₀ = -1.9200 × 10 ^-10 14th surface K = 0 A ₄ = -1.1041 × 10 ^-4 A ₆ = -2.7188 × 10 ^-6 A ₈ = 3.7776 × 10 ^-7 A ₁₀ = 0 | F ₂ / F ₃ | = 0.779 F ₃ / F ₄ = 0.794 | β _2T | _{= 0.586 | L 3 / L 2} | = 0.792 (F 3,4W) / IH = 2.71 F 1 / IH = 9.98
.

[0063] Example 5 f = 5.504 ~ 9.432 ~ 15.856 F NO = 1.990 ~ 2.270 ~ 2.711 r 1 = 18.2001 d 1 = 1.1730 n d1 = 1.80518 ν d1 = 25.42 r 2 = 13.0296 d 2 = 0.3357 r 3 = 13.9728 d _{3 = 4.8470 n d2 = 1.69680 ν} d2 = 55.53 r 4 = 3102.7527 d 4 = ( _{variable) r 5 = 424.6070 d 5 =} 0.8000 n d3 = 1.77250 ν d3 = 49.60 r 6 = 5.6105 d 6 = 2.9586 r 7 = -105.0017 _{d 7 = 0.8000 n d4 = 1.48749} ν d4 = 70.23 r 8 = 10.6618 d 8 = 2.3225 n d5 = 1.72250 ν d5 = 29.20 r 9 = 74.1193 ( aspherical) d ₉ = (variable) r ₁₀ = ∞ (stop) d ₁₀ = (variable) r ₁₁ = 9.2181 _{(aspherical) d 11 = 2.9948 n d6 =} 1.66910 ν d6 = 55.40 r 12 = -30.4447 d 12 = 0.1424 r 13 = 7.5345 d 13 = 2.5546 n d7 = 1.67790 ν d7 = 55.34 _{r 14 = 80.3022 d 14 = 0.7000} n d8 = 1.84666 ν d8 = 23.78 r 15 = 4.9693 d 15 = ( variable) r ₁₆ = 9.4973 _{(aspherical) d 16 = 2.8365 n d9 =} 1.66910 ν d9 = 55.40 r 17 = - 38.4689 Aspheric surface ninth surface K = 0 A ₄ = -2.6558 × 10 ^-4 A ₆ = 4.2392 × 10 ^-6 A ₈ = -5.44464 × 10 ^-7 A ₁₀ = 1.2756 × 10 ^-8 Eleventh surface K = -0.2184 A ₄ = -1.8121 × 10 ^-4 A ₆ = -1.3295 × 10 ^-6 A ₈ = 1.4549 × 10 ^-7 A ₁₀ = -4.6461 × 10 ^-9 Surface 16 K = 0 A ₄ = -2.5114 × 10 ^-4 A ₆ = 3.1103 × 10 ^-6 A ₈ = -1.1345 × 10 ^-8 A ₁₀ = 0 | F ₂ / F ₃ | = 0.628 F ₃ / F ₄ = 1.088 | β _2T | = 0.760 | L ₃ / L ₂ | _{= 0.54 (F 3,4W) / IH} = 2.67 F 1 / IH = 8.73
.

[0064] Example 6 f = 6.608 ~ 11.270 ~ 19.098 F NO = 2.03 ~ 2.36 ~ 2.91 r 1 = 36.688 d 1 = 4.14 n d1 = 1.48749 ν d1 = 70.23 r 2 = ∞ d 2 = ( Variable) r ₃ = _{21.750 d 3 = 1.25 n d2 =} 1.84666 ν d2 = 23.78 r 4 = 8.054 d 4 = 5.45 r 5 = -27.511 d 5 = 1.00 n d3 = 1.48749 ν d3 = 70.23 r 6 = 10.412 d 6 = 4.50 n d4 = 1.84666 _{ν d4 = 23.78 r 7 = 40.550} d 7 = ( variable) r ₈ = ∞ (stop) d ₈ = (variable) r ₉ = 17.583 _{(aspherical) d 9 = 3.42 n d5 =} 1.58913 ν d5 = 61.30 r 10 = _{-35.670 d 10 = 0.20 r 11 =} 9.390 d 11 = 4.35 n d6 = 1.77250 ν d6 = 49.60 r 12 = 87.943 d 12 = 0.90 n d7 = 1.84666 ν d7 = 23.78 r 13 = 6.609 d 13 = ( variable) r ₁₄ = 13.553 (aspherical surface) d ₁₄ = 3.28 n _d8 = 1.58913 ν _d8 = 61.30 r ₁₅ = -30.808 Aspheric surface ninth surface K = 0.000 A ₄ = -4.66054 × 10 ^-5 A ₆ = -1.33346 × 10 ^-6 A ₈ = 6.88261 × 10 ^-8 A ₁₀ = -1.18171 × 10 ^-9 A ₁₂ = 1.21868 × 10 ^-12 14th surface _{K = 0.000 A 4 = -9.93375 ×} 10 -5 A 6 = -9.76311 × 10 -7 A 8 = 3.21037 × 10 -7 A 10 = -1.95172 × 10 -8 A 12 = 3.74139 × 10 - ^{_{10 | F 2 / F 3 |}} = 0.77 F 3 / F 4 = 1.12 | β 2T | = 0.35 | L 3 / L 2 | = 0.48 (F 3,4W) / IH = 3.06 F 1 / IH = 17.10
.

[0065] Example 7 f = 6.613 ~ 11.256 ~ 18.999 F NO = 2.64 ~ 3.01 ~ 3.85 r 1 = 27.567 d 1 = 4.40 n d1 = 1.48749 ν d1 = 70.23 r 2 = ∞ d 2 = ( Variable) r ₃ = _{34.610 d 3 = 1.00 n d2 =} 1.84666 ν d2 = 23.78 r 4 = 7.611 d 4 = 4.17 r 5 = -26.015 d 5 = 0.95 n d3 = 1.48749 ν d3 = 70.23 r 6 = 9.781 d 6 = 3.36 n d4 = 1.84666 _{ν d4 = 23.78 r 7 = 77.491} d 7 = ( variable) r ₈ = ∞ (stop) d ₈ = (variable) r ₉ = 9.059 _{(aspherical) d 9 = 3.46 n d5 =} 1.58913 ν d5 = 61.28 r 10 = _{-28.867 d 10 = 0.20 r 11 =} 13.765 d 11 = 3.12 n d6 = 1.77250 ν d6 = 49.60 r 12 = 81.243 d 12 = 0.90 n d7 = 1.84666 ν d7 = 23.78 r 13 = 6.376 d 13 = ( variable) r _{14 = 16.883 d 14 = 2.54 n d8} = 1.80400 ν d8 = 46.57 r 15 = -22.639 d 15 = 0.90 r 16 = -13.830 d 16 = 1.00 n d9 = 1.84666 ν d9 = 23.78 r 17 = -20.854 Aspheric surface ninth surface K = 0.000 A ₄ = -2.444569 × 10 ^-4 A ₆ = 1.63587 × 10 ^-6 A ₈ = -2.54 100 × 10 ^-7 A ₁₀ = 1.25155 × 10 ^-8 A ₁₂ = -2.30862 _{^{× 10 -10 | F 2 / F}} 3 | = 0.76 F 3 / F 4 = 1.09 | β 2T | = 0.50 | L 3 / L 2 | = 0.55 (F 3,4W) / IH = 2.79 F 1 / IH = 12.85
.

[0066] Example 8 f = 6.548 ~ 11.266 ~ 19.000 F NO = 2.02 ~ 2.33 ~ 2.80 r 1 = 28.972 d 1 = 1.50 n d1 = 1.84666 ν d1 = 23.78 r 2 = 19.691 d 2 = 0.22 r 3 = 20.405 d _{3 = 4.96 n d2 = 1.77250 ν} d2 = 49.60 r 4 = 196.549 d 4 = ( _{variable) r 5 = 42.098 d 5 =} 1.00 n d3 = 1.77250 ν d3 = 49.60 r 6 = 7.090 d 6 = 4.71 r 7 = -42.112 _{d 7 = 0.95 n d4 = 1.57250} ν d4 = 57.74 r 8 = 7.798 d 8 = 3.63 n d5 = 1.80100 ν d5 = 34.97 r 9 = 51.433 d 9 = ( variable) r ₁₀ = ∞ (stop) d ₁₀ = (variable ) r ₁₁ = 13.438 _{(aspherical) d 11 = 2.85 n d6 =} 1.58913 ν d6 = 61.30 r 12 = -33.468 d 12 = 0.20 r 13 = 16.565 d 13 = 5.00 n d7 = 1.77250 ν d7 = 49.60 r 14 = - 9.106 d ₁₄ = 0.90 n _d8 = 1.68893 ν _d8 = 31.07 r ₁₅ = 7.645 d ₁₅ = (variable) r ₁₆ = 13.914 (aspherical surface) d ₁₆ = 5.00 _{nd 9} = 1.58913 ν _d9 = 61.30 r ₁₇ = -26.414 Aspheric coefficient 11th surface K = 0.000 A ₄ = -1.15802 × 10 ^-4 A ₆ = -2.30929 × 10 ^-6 A ₈ = 9.29778 × 10 ^-8 A ₁₀ = -1.70572 × 10 ^-9 16th surface K = 0.000 ^{_{A 4 = -1.50902 × 10 -4 A}} 6 = 7.59738 × 10 -6 A 8 = -4.34345 × 10 -7 A 10 = 9.20410 × 10 -9 | F 2 / F 3 | = 0.64 F 3 / F 4 = 1.07 | Β _2T | = 0.56 | L ₃ / L ₂ | = 0.52 (F _3,4W ) _/IH=2.81 F _{1 /IH=10.96}
.

[0067] Example 9 f = 6.562 ~ 11.266 ~ 19.000 F NO = 2.03 ~ 2.41 ~ 2.98 r 1 = 27.565 d 1 = 1.80 n d1 = 1.84666 ν d1 = 23.78 r 2 = 22.250 d 2 = 5.28 n d2 = 1.69680 ν _{d2 = 55.53 r 3 = 146.290 d} 3 = ( _{variable) r 4 = 33.155 d 4 =} 1.20 n d3 = 1.84666 ν d3 = 23.78 r 5 = 7.643 d 5 = 5.94 r 6 = -32.864 d 6 = 0.95 n d4 = 1.58913 _{ν d4 = 61.14 r 7 = 9.442} d 7 = 5.00 n d5 = 1.84666 ν d5 = 23.78 r 8 = 72.713 d 8 = ( variable) r ₉ = ∞ (stop) d ₉ = (variable) r ₁₀ = 13.995 (aspherical _{) d 10 = 4.65 n d6 =} 1.58913 ν d6 = 61.30 r 11 = -26.315 d 11 = 0.20 r 12 = 11.896 d 12 = 5.00 n d7 = 1.77250 ν d7 = 49.60 r 13 = -19.763 d 13 = 0.90 n d8 = 1.80518 ν _d8 = 25.42 r ₁₄ = 7.049 d ₁₄ = (variable) r ₁₅ = 12.657 (aspherical surface) d ₁₅ = 5.00 _{nd 9} = 1.58913 ν _d9 = 61.30 r ₁₆ = -36.523 Aspheric coefficient 10th surface K = 0.000 A ₄ = -8.42531 × 10 ^-5 A ₆ = -1.06102 × 10 ^-6 A ₈ = 4.82414 × 10 ^-8 A ₁₀ = -7.21004 × 10 ^-10 15th surface K = 0.000 ^{_{A 4 = -1.53723 × 10 -4 A}} 6 = 8.03934 × 10 -6 A 8 = -4.64104 × 10 -7 A 10 = 9.96594 × 10 -9 | F 2 / F 3 | = 0.72 F 3 / F 4 = 0.96 | Β _2T | = 0.55 | L ₃ / L ₂ | = 0.61 (F _3,4W ) _/IH=2.73 F _{1 /IH=11.41}
.

[0068] Example 10 f = 6.460 ~ 11.267 ~ 19.000 F NO = 2.03 ~ 2.36 ~ 2.86 r 1 = 45.399 d 1 = 1.50 n d1 = 1.84666 ν d1 = 23.78 r 2 = 30.450 d 2 = 3.42 n d2 = 1.77250 ν _{d2 = 49.60 r 3 = 73.068 d} 3 = 0.20 r 4 = 30.537 d 4 = 4.00 n d3 = 1.60311 ν d3 = 60.64 r 5 = 114.998 d 5 = ( _{variable) r 6 = 37.983 d 6 =} 1.00 n d4 = 1.80610 ν _{d4 = 40.92 r 7 = 7.134 d} 7 = 4.94 r 8 = -34.697 d 8 = 0.95 n d5 = 1.59551 ν d5 = 39.24 r 9 = 7.910 d 9 = 3.74 n d6 = 1.80518 ν d6 = 25.42 r 10 = 61.919 d 10 = (variable) r ₁₁ = ∞ (stop) d ₁₁ = (variable) r ₁₂ = 20.148 _{(aspherical) d 12 = 3.82 n d7 =} 1.58913 ν d7 = 61.30 r 13 = -27.415 d 13 = 0.20 r 14 = 11.775 _{d 14 = 5.00 n d8 = 1.77250} ν d8 = 49.60 r 15 = -16.598 d 15 = 0.90 n d9 = 1.74077 ν d9 = 27.79 r 16 = 7.678 d 16 = ( variable) r ₁₇ = 14.447 (aspherical) d ₁₇ = 5.00 n _d10 = 1.58913 ν _d10 = 61.30 r ₁₈ = -24.089 Aspheric surface twelfth surface K = 0.000 A ₄ = -4.884618 × 10 ^-5 A ₆ = -1.550477 × 10 ^-6 A ₈ = 6.27337 × 10 ^-8 A ₁₀ = -9.773311 × 10 ^-10 Seventeenth surface K = 0.000 ^{_{A 4 = -1.24232 × 10 -4 A}} 6 = 4.55032 × 10 -6 A 8 = -2.09257 × 10 -7 A 10 = 3.76691 × 10 -9 | F 2 / F 3 | = 0.59 F 3 / F 4 = 1.08 | Β _2T | = 0.55 | L ₃ / L ₂ | = 0.61 (F _3,4W ) _/IH=2.96 F _{1 /IH=11.19}
.

FIGS. 12 and 13 show aberration diagrams at the wide-angle end and the telephoto end when the zoom lens of the first embodiment is focused on an object point at infinity. In these figures, (a) shows spherical aberration, (b) shows astigmatism, (c) shows distortion, (d) shows chromatic aberration of magnification, and (e) shows coma.

The above-described zoom lens of the present invention can be constituted, for example, as follows. [1] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and a second lens unit having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end during zooming. A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

0.5 <| F ₂ / F ₃ | <1.2 (1) where F _i is the focal length of the i-th lens unit.

[2] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end at zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

0.49 <| L ₃ / L ₂ | <1 (2) Here, _Li is the amount of movement of the i-th lens unit from the wide-angle end to the telephoto end.

[3] A first lens unit having a positive refractive power and fixed at the time of zooming in order from the object side, and having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end at zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

2 <(F _3,4W ) / IH <3.3 (3) where (F _3,4W ) is the combined focal length of the third and fourth _units at the wide-angle end, and IH is Image circle radius.

[4] A first lens unit having a positive refractive power in order from the object side, and a second lens unit having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end during zooming, A third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power and movable during zooming, wherein the third lens unit includes a positive lens having a convex surface facing the object side in order from the object side, A positive lens having a convex surface facing the lens side and a cemented lens of a negative lens having a concave surface facing the image surface side, wherein both the positive lens and the cemented lens on the object side of the third group are peripheral portions of the convex surface facing the object side Characterized in that the zoom lens is held in a state where it is applied to the lens frame on the circumference or at several places on the circumference.

[5] A first lens unit having a positive refractive power and fixed at the time of zooming in order from the object side, and having a negative refractive power and moving from the object side to the image surface side from the wide-angle end to the telephoto end at zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

0.5 <| F ₂ / F ₃ | <1.2 (1) 0.49 <| L ₃ / L ₂ | <1 (2) where _Fi is the first The focal length L _i of the i-th lens unit is the amount of movement of the i-th lens unit from the wide-angle end to the telephoto end.

[6] A first lens unit having a positive refractive power and fixed at the time of zooming in order from the object side, and having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end during zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

[0080] _{0.5 <| F 2 / F 3} | <1.2 ··· (1) 2 <(F 3,4W) / IH <3.3 ··· (3) where, F _i is The focal length of the i-th lens unit, (F _3,4W ) is the combined focal length of the third and fourth lens _units at the wide-angle end, and IH is the radius of the image circle.

[7] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end at zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

[0082] _{0.49 <| L 3 / L 2} | <1 ··· (2) 2 <(F 3,4W) / IH <3.3 ··· (3) where, L _i is the i-th The amount of movement of the group from the wide-angle end to the telephoto end, (F _3,4W ) is the combined focal length of the third and fourth groups at the wide-angle end, and IH is the image circle radius.

[8] In order from the object side, a first lens unit having a positive refractive power and fixed during zooming, and having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end during zooming. Second
A third lens unit having a positive refractive power and moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens group having a positive refractive power and movable during zooming. A zoom lens characterized by satisfying the following conditional expression.

0.5 <| F ₂ / F ₃ | <1.2 (1) 0.49 <| L ₃ / L ₂ | <1 (2) 2 <(F _3,4W ) / IH <3.3 (3) where F _i is the focal length of the i-th lens unit, L _i is the amount of movement of the i-th lens unit from the wide-angle end to the telephoto end, and (F _3,4W ) is The composite focal length of the third and fourth units at the wide-angle end, IH, is the image circle radius.

[0085]

[9] The zoom lens according to any one of [1], [2], [3], and [5] to [8], wherein the following conditional expression is satisfied.

0.6 <| F ₂ / F ₃ | <1 (4) where F _i is the focal length of the i-th lens unit.

[10] Focusing is performed by moving the fourth lens unit in the direction of the optical axis.
[2], [3], [5] ~

The zoom lens according to any one of [9].

[11] The above conditions [1], [2], [3], [5] to [10] characterized by satisfying the following conditional expressions:
The zoom lens according to any one of the preceding claims.

0.3 <F ₃ / F ₄ <0.8 (5) where _Fi is the focal length of the i-th lens unit.

[12] The following [1], [2], [3], [5] to [11] characterized by satisfying the following conditional expressions:
The zoom lens according to any one of the preceding claims.

0.4 <| β _2T | <1 (6) Here, β _2T is a lateral magnification of the second lens unit at the telephoto end.

[13] The above-mentioned [1], [2], [3], and [5], wherein the fourth group comprises one positive lens.
-The zoom lens according to any one of [12].

[14] The above-mentioned [1], [2], [3], [5] to [3], wherein the third unit is composed of three positive, positive and negative lenses in order from the object side. Any one of [13]
The zoom lens described in the item.

[15] At least one surface of the third group is aspherical, [1], [2],
[3] The zoom lens according to any one of [5] to [14].

[16] At least one surface of the fourth group is aspherical, [1], [2],
[3] The zoom lens according to any one of [5] to [15].

[17] At least one surface of the second group is aspherical, [1], [2],
[3] The zoom lens according to any one of [5] to [16].

[18] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end at zooming. A second lens unit having a positive refractive power, a third lens unit moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. The first group is composed of one positive lens, and the most object side of the second group is a negative lens;
A zoom lens characterized by satisfying the following conditional expression.

Ν ₂₁ <40 (7) Here, ν ₂₁ is the Abbe number of the negative lens closest to the object side in the second group.

[19] The zoom lens according to the above [18], wherein the following conditional expression is satisfied.

Ν ₂₁ <35 (8) [20] Any one of the above [1], [2], [3], [5] to [17], characterized by satisfying the following conditional expression: 1
The zoom lens described in the item.

Ν ₂₁ <40 (7) Here, ν ₂₁ is the Abbe number of the negative lens closest to the object side in the second group.

[21] The above-mentioned [1], [2], [3], [5] to [17] characterized by satisfying the following conditional expressions:
The zoom lens according to any one of the preceding claims.

Ν ₂₁ <35 (8) Here, ν ₂₁ is the Abbe number of the negative lens closest to the object side in the second group.

[22] The third unit is composed of, in order from the object side, a positive lens having a convex surface facing the object side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image surface side. The third lens unit, wherein the positive lens on the object side and the cemented lens of the third group are both held in a state in which the peripheral portion of the convex surface facing the object side is applied to the lens frame at or around the periphery thereof. Features [1], [2], [3], [5]-
The zoom lens according to any one of [20].

[23] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image surface side from the wide angle end to the telephoto end at zooming. A second lens unit having a positive refractive power, a third lens unit constantly moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. Wherein the third group includes a cemented lens including a positive lens and a negative lens, and the fourth group includes one positive lens.

[24] The above-mentioned [23], wherein at least one surface of the fourth group of positive lenses is aspheric.
The zoom lens described.

[25] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image surface side from the wide angle end to the telephoto end at zooming. A second lens unit having a positive refractive power, a third lens unit constantly moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. Wherein the second group and the third group each have a cemented lens composed of a positive lens and a negative lens.

[26] In order from the object side, a first lens unit having a positive refractive power and fixed at the time of zooming, and having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end at zooming. A second lens unit having a positive refractive power, a third lens unit constantly moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. Wherein the third unit is composed of a positive lens from the object side, and a cemented lens including a positive lens and a negative lens.

[27] In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power At the time of zooming, the distance between the first group and the second group, the distance between the second group and the third group,
The distance between the third lens unit and the fourth lens unit changes, and the third lens unit includes, in order from the object side, a biconvex positive lens and a cemented lens of a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens. Wherein the fourth group is composed of a biconvex lens having a large curvature on the object side surface.

[28] In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power At the time of zooming, the distance between the first group and the second group, the distance between the second group and the third group,
The distance between the third group and the fourth group changes, and the first group includes one positive lens. The second group includes, in order from the object side, a single lens and a cemented negative lens and positive lens. The third group includes, in order from the object side, a single lens and a cemented lens of a positive lens and a negative lens, and the third group includes one lens. A zoom lens comprising a number of positive lenses.

[29] In order from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power At the time of zooming, the distance between the first group and the second group, the distance between the second group and the third group,
The distance between the third group and the fourth group changes, and the first group includes two lenses, a positive lens and a negative lens, and at least one set of a positive lens and a negative lens in the second group or the third group. A zoom lens comprising a cemented lens of claim 1.

[0112]

As is apparent from the above description, according to the present invention, it is possible to provide a small and low-cost zoom lens.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a first embodiment of the present invention at a wide-angle end.

FIG. 2 is a cross-sectional view at a wide-angle end of a zoom lens according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view at a wide-angle end of a zoom lens according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view at a wide-angle end of a zoom lens according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view at a wide-angle end of a zoom lens according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a zoom lens according to a sixth embodiment of the present invention at the wide-angle end.

FIG. 7 is a sectional view of a zoom lens according to a seventh embodiment of the present invention at the wide-angle end.

FIG. 8 is a sectional view of a zoom lens according to a eighth embodiment of the present invention at the wide-angle end.

FIG. 9 is a sectional view of a zoom lens according to a ninth embodiment of the present invention at the wide-angle end.

FIG. 10 is a sectional view of a zoom lens according to a tenth embodiment of the present invention at the wide-angle end.

FIG. 11 is a diagram illustrating a third group holding structure according to a fifth embodiment.

FIG. 12 is an aberration diagram at a wide-angle end in Example 1.

13 is an aberration diagram at a telephoto end in Example 1. FIG.

[Explanation of symbols]

G1 ... cemented lens 1 ... holding frame of the first group G2 ... positive lens L ₃₂ ... third group in the second group G3 ... third group G4 ... fourth group S ... aperture L ₃₁ ... third group

Claims (3)

[Claims] 1. A first group fixed at the time of zooming having a positive refractive power and having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end at zooming in order from the object side. A second lens unit having a positive refractive power, a third lens unit moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. And a zoom lens satisfying the following conditional expression. _{0.5 <| F 2 / F 3} | <1.2 ··· (1) where, F _i is the focal length of the i group. 2. A first group fixed at the time of zooming having a positive refractive power and having a negative refractive power and moving from the object side to the image plane side from the wide angle end to the telephoto end at zooming in order from the object side. A second lens unit having a positive refractive power, a third lens unit moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming. And a zoom lens satisfying the following conditional expression. 0.49 <| L ₃ / L ₂ | <1 (2) where _Li is the movement amount of the i-th lens unit from the wide-angle end to the telephoto end. 3. A first unit fixed at the time of zooming having a positive refractive power and having a negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end at zooming, in order from the object side. A second lens unit having a positive refractive power, a third lens unit moving from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit having a positive refractive power and movable during zooming And a zoom lens satisfying the following conditional expression. 2 <(F _3,4W ) / IH <3.3 (3) where (F _3,4W ) is the combined focal length of the third and fourth _units at the wide-angle end, and IH is the radius of the image circle. It is.