JP2009150970A - Zoom lens and imaging device provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact zoom lens having a simple configuration while securing a high zoom ratio. <P>SOLUTION: This zoom lens has a group of first lenses having positive refractive power, a group of second lenses having negative refractive power, a group of third lenses having positive refractive power, and a group of fourth lenses having positive refractive power arranged sequentially in this order from an object side to an image side. All of the groups of the first to fourth lenses can move for zooming. When zooming, the group of the first lenses move to be positioned on the object side at a telescopic end more farther compared with a wide angle end. The group of the first lenses is composed of one lens. Each of a focal distance fw of the whole system at a wide angle end, a focal distance f2 of the group of the second lenses, and an Abbe number νd4 of a material of at least one positive lens included in the group of the fourth lenses is properly set. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a zoom lens and an imaging apparatus having the same, and is suitable for, for example, a silver salt photography camera, a video camera, a digital still camera, and the like.

  In recent years, imaging devices such as a video camera using a solid-state imaging device, a digital still camera, a broadcasting camera, and a still camera using a silver salt film have been improved in function, and the entire device has been downsized.

  As a photographic lens used therefor, it is required that the zoom lens has a short overall lens length, a compact overall system, and high optical performance.

  In addition, the imaging device is required to have a relatively long back focus (distance from the final surface of the imaging lens to the imaging surface) in order to arrange an optical filter, a quick return mirror, etc. on the light incident side of the imaging means. ing.

  As an example of a zoom lens that meets these requirements, a four-unit zoom that includes four lens groups of positive, negative, positive, and positive refractive power in order from the object side to the image side, and performs zooming by moving each lens group. The lens is known.

  Among the four-group zoom lenses, there is known a zoom lens having a high zoom ratio of about 3.5 times the zoom ratio while the entire system is compact (for example, Patent Document 1).

  Further, in order from the object side to the image side, the lens unit includes four lens units having positive, negative, positive, and positive refractive powers. The first lens unit includes one lens, and mainly the second and third lenses. A small four-group zoom lens that performs zooming by moving a lens group is known (for example, Patent Document 2).

On the other hand, there is known a zoom lens in which a part of a lens group is displaced in a direction perpendicular to the optical axis to correct image blur when the zoom lens vibrates. For example, in a zoom lens having a four-group configuration including first, second, third, and fourth lens groups having positive, negative, positive, and positive refractive powers in order from the object side to the image side, a part of the third lens group is A zoom lens that obtains a still image by vibrating in a direction perpendicular to the optical axis is known (Patent Document 3).
JP 2004-333770 A JP 2002-72087 A Japanese Patent Laid-Open No. 07-128619

  In general, in order to reduce the size of the entire zoom lens system and obtain a high zoom ratio, the refractive power of each lens constituting the zoom lens may be increased. However, simply increasing the refractive power of the lens group degrades the optical performance. Further, in order to maintain good optical performance, each lens group requires a large number of lenses. As a result, it is difficult to reduce the size of the entire zoom lens system.

  In particular, in the above-described four-group zoom lens, in order to obtain high optical performance over the entire zoom range while ensuring a high zoom ratio while reducing the size of the entire system, the refractive power of the second lens group and the fourth lens group It is important to set the lens configuration and the like appropriately.

  Furthermore, it is important to appropriately set the refractive power of the first lens group and the amount of movement of the first and fourth lens groups during zooming.

  If these elements are set inappropriately, aberration fluctuations associated with zooming will increase, especially chromatic aberration fluctuations, and it will be difficult to achieve high optical performance over the entire zoom range while miniaturizing the entire system. It becomes.

  As described above, in a zoom lens, it is a contradictory condition to reduce the size of the entire optical system and to obtain high optical performance, and it is an important issue for the zoom lens to achieve both of them.

  An object of the present invention is to provide a zoom lens with a simple lens configuration and a small overall size while ensuring a high zoom ratio by appropriately setting the refractive power and lens configuration of each lens group.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens having a positive refractive power. Having a fourth lens group;
A zoom lens that performs zooming by moving all of the first lens group to the fourth lens group,
During zooming, the first lens unit moves to be positioned closer to the object side at the telephoto end than at the wide-angle end,
The first lens group consists of one lens,
When the focal length of the entire system at the wide angle end is fw, the focal length of the second lens group is f2, and the Abbe number of the material of at least one positive lens included in the fourth lens group is νd4,
30.0 <νd4 <60.0
−1.20 <f2 / fw <−0.80
It is characterized by satisfying the following conditions.

  According to the present invention, it is possible to realize a small zoom lens with a simple configuration while ensuring a high zoom ratio.

  Embodiments of a zoom lens and an image pickup apparatus having the same according to the present invention will be described below in detail with reference to the accompanying drawings.

  The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens having a positive refractive power. A fourth lens group is included. All of the first lens group to the fourth lens group move to perform zooming. The first lens group is composed of a single lens, and moves during zooming so that it is positioned closer to the object side at the telephoto end than at the wide-angle end.

  FIG. 1 is a lens cross-sectional view at the wide-angle end (short focal length end) of the zoom lens according to Embodiment 1 of the present invention. FIGS. 2A to 2C are aberration diagrams when the zoom lens of Example 1 is in focus at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end (long focal length end), respectively. .

  FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 2 of the present invention. FIGS. 4A to 4C are aberration diagrams when the zoom lens of Example 2 is in an infinite object focusing state at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. FIGS. 6A to 6C are aberration diagrams when the zoom lens of Example 3 is in the infinite object focusing state at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens according to a fourth exemplary embodiment of the present invention. 8A to 8C are aberration diagrams when the zoom lens of Example 4 is in an infinite object focusing state at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIG. 9 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 5 of the present invention. FIGS. 10A to 10C are aberration diagrams when the zoom lens of Example 5 is in focus at infinity at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively.

  FIG. 11 is a schematic diagram of a main part of a camera (image pickup apparatus) including the zoom lens according to the present invention.

  The zoom lens of each embodiment is a photographing lens system used in an imaging apparatus such as a digital still camera or a silver salt film camera. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear).

  When used in a projector, the left side is the screen (projected surface) and the right side is the projected image side. In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group.

  The arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end.

  SP is an aperture stop that moves integrally with the third lens unit L3 during zooming. FS is a flare-cut stop. In each embodiment, it is fixed during zooming, but it may be moved independently during zooming or integrally with an adjacent lens group.

  IP is an image plane. When used as a photographing optical system for a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, or a camera for a silver salt film It corresponds to a photosensitive surface such as a film surface.

  In the aberration diagrams, d and g are d-line and g-line, respectively, and S.C. is a sine condition. ΔM and ΔS are the d-line meridional image surface and sagittal image surface. Lateral chromatic aberration is represented by the g-line. fno is an F number. ω is a half angle of view (degree).

  In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the zoom lens unit is positioned at both ends of a range in which the mechanism can move on the optical axis.

  Next, features of the lens configuration of the zoom lenses of Embodiments 1 to 5 will be described.

  First, Examples 1, 2, and 3 in FIGS. 1, 3, and 5 will be described.

  In Examples 1, 2, and 3 of FIGS. 1, 3, and 5, L1 is a first lens unit having a positive refractive power (optical power = reciprocal of focal length), and L2 is a second lens having a negative refractive power. A lens group, L3 is a third lens group having a positive refractive power, and L4 is a fourth lens group having a positive refractive power.

  The third lens unit L3 includes a third-a lens component L3a having a positive refractive power and a third-b lens component L3b having a negative refractive power.

  In Examples 1, 2, and 3, the lens groups L1 to L4 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.

  Specifically, the first, third, and fourth lens groups L1, L3, and L4 are moved to the object side.

  The 3a lens component L3a and the 3b lens component L3b are moved together.

  The second lens unit L2 moves so as to draw a convex locus toward the image side.

  At this time, the distance between the first lens unit L1 and the second lens unit L2 is larger at the telephoto end than at the wide angle end, the interval between the second lens unit L2 and the third lens unit L3 is small, and the third lens unit L3 and the third lens unit L3. Each lens group is moved so that the interval between the four lens groups L4 is reduced.

  During zooming, the first lens unit L1 and the third lens unit L3 are moved so as to be positioned closer to the object side at the telephoto end than at the wide-angle end, so that the entire lens length at the wide-angle end is kept small and large. A zoom ratio (high zoom ratio) is obtained.

  In particular, when the first lens unit L1 is positioned on the image side at the wide-angle end where the angle of view is large, an increase in the front lens diameter is prevented, and the first lens unit L1 having a large lens diameter is configured by a single lens. Miniaturization has been achieved.

  In Examples 1, 2, and 3, the third lens unit L3 is provided with a zooming effect by moving the third lens unit L3 to the object side during zooming from the wide-angle end to the telephoto end. Further, the first lens unit L1 having a positive refractive power is moved so as to be positioned closer to the object side at the telephoto end than at the wide angle end. As a result, the second lens unit L2 has a large zooming effect, and a high zoom ratio of about 4 times is obtained without increasing the refractive power of the first lens unit L1 and the second lens unit L2.

  Further, an inner focus type in which focusing is performed by moving the second lens unit L2 on the optical axis is adopted.

  When focusing from an infinitely distant object to a close object at the telephoto end, the second lens unit L2 is moved forward as indicated by an arrow 2c. A solid curve 2a and a dotted curve 2b relating to the second lens unit L2 are for correcting image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and an object at close distance, respectively. The movement trajectory is shown.

  In Examples 1, 2, and 3, the image is displaced in the direction perpendicular to the optical axis by moving the 3b lens component L3b so as to have a component perpendicular to the optical axis. As a result, image blur when the entire optical system vibrates is corrected.

  That is, vibration isolation is performed.

  As a result, image stabilization is performed without newly adding an optical member such as a variable apex angle prism or a lens group for image stabilization, and the entire optical system is prevented from being enlarged.

  The aperture stop SP moves together with the third lens unit L3 during zooming. As a result, the number of groups divided by movement / movability is reduced, and the mechanical structure is simplified.

  Next, Example 4 in FIG. 7 will be described.

  In the fourth embodiment, compared to the first, second, and third embodiments, the 3a lens component L3a and the 3b lens component (lenses positioned closest to the image side of the third lens unit L3) L3b during zooming from the wide-angle end to the telephoto end Is different in that it moves independently to the object side.

  Other configurations are the same as those of the first, second, and third embodiments.

  The fourth exemplary embodiment can also be handled as a five-unit zoom lens including a lens unit having positive, negative, positive, negative, and positive refractive powers in order from the object side to the image side.

  In Example 4, zooming is performed by moving all the lens groups independently. However, the mechanical configuration may be simplified by making the movement locus of the third lens component L3a and the fourth lens group L4 the same. .

  Next, Example 5 of FIG. 9 will be described. The fifth embodiment is different from the first, second, and third embodiments in that a fifth lens unit L5 having a negative refractive power is provided on the image side of the fourth lens unit L4.

  That is, in Example 5 of FIG. 9, L1 is a first lens unit having a positive refractive power, L2 is a second lens unit having a negative refractive power, L3 is a third lens unit having a positive refractive power, and L4 is a positive lens unit. A fourth lens unit having a refractive power, and L5 is a fifth lens unit having a negative refractive power.

  The movement form of the first lens unit L1 to the fourth lens unit L4 during zooming is the same as in the first, second, and third embodiments. The fifth lens unit L5 does not move during zooming. The focus is the same as in the first, second, and third embodiments.

  Next, the characteristics of the lens configuration common to the embodiments will be described.

  In each embodiment, the entire refractive power arrangement at the wide-angle end is a substantially retrofocus type refractive power arrangement.

  Further, the entire refractive power arrangement at the telephoto end is made to be a substantially telephoto type refractive power arrangement. As a result, a zoom lens realizing a high zoom ratio is obtained.

  Also, efficient distribution of refractive power is facilitated by moving at least the first to fourth lens units L1 to L4 to correct image plane variation accompanying zooming and zooming.

  Furthermore, the overall optical length can be shortened while ensuring a relatively long back focus at the wide-angle end. Thus, for example, a compact zoom lens is configured with a high zoom ratio that is optimal as an interchangeable lens for a single lens reflex camera.

  In each embodiment, focusing is performed by moving the second lens unit L2 along the optical axis, but may be performed by another lens unit (for example, the first lens unit L1 or the fourth lens unit L4). good.

  In each embodiment, the first lens unit L1 having a positive refractive power is a lens unit having the largest effective diameter. The first lens unit L1 has a single lens configuration (excluding a cemented lens), thereby realizing a compact zoom lens.

  The second lens unit L2 having a negative refractive power is composed of two negative lenses and one positive lens. Since the second lens unit L2 has a large variable magnification share and is a focus lens unit, the second lens unit L2 alone corrects aberrations to some extent.

  Since the second lens unit L2 has a strong negative refractive power, it is difficult to correct aberrations with one negative lens and one positive lens. Therefore, one negative lens is divided into two negative lenses. ing.

  The third lens unit L3 having a positive refractive power is a lens unit in which an axial ray passes through a relatively high position in the entire zoom region. For this reason, the positive lens and the negative lens are provided so that the axial aberration generated in the positive lens is corrected by the negative lens.

  The fourth lens unit L4 having a positive refractive power uses an aspherical lens, and corrects on-axis and off-axis aberrations that could not be corrected by the third lens unit L3.

  As described above, by appropriately setting the moving condition of each lens group in zooming, the refractive power of each lens group, and the like, it is possible to easily reduce the overall length of the lens despite the high zoom ratio.

  In each embodiment, the following conditional expressions (1) and (2) are satisfied simultaneously in order to reduce the size of the entire system while correcting chromatic aberration.

Let fw be the focal length of the entire system at the wide-angle end. Let the focal length of the second lens unit L2 be f2. The Abbe number of the material of at least one positive lens included in the fourth lens unit L4 is νd4. At this time,
30.0 <νd4 <60.0 (1)
−1.20 <f2 / fw <−0.80 (2)
Is satisfied.

  Conditional expression (1) relates to the Abbe number of the material of the positive lens included in the fourth lens unit L4. The chromatic aberration caused by configuring the first lens unit L1 with one lens is expressed by the wide-angle end and the telephoto end. This is a condition for correcting with good balance at the zoom position.

  When the lower limit value of conditional expression (1) is exceeded, the correction of axial chromatic aberration and lateral chromatic aberration becomes excessive at the wide angle end.

  If the upper limit is exceeded, it becomes difficult to satisfactorily correct lateral chromatic aberration at the telephoto end.

  In order to correct chromatic aberration, it is more preferable to set the numerical range of conditional expression (1) as follows.

35.0 <νd4 <53.2 (1a)
Conditional expression (2) relates to the ratio between the focal length of the second lens unit L2 and the focal length of the entire system at the wide angle end. By appropriately setting the focal length of the second lens unit L2, the entire lens system can be reduced in size and optical performance can be maintained in a well-balanced manner.

  If the lower limit of the conditional expression (2) is exceeded, the negative refractive power of the second lens unit L2 becomes weak, so that a desired zoom ratio is ensured between the first lens unit L1 and the third lens unit L3. It is necessary to increase the amount of change in the air spacing. If it does so, since the whole optical system will enlarge, it is not preferable.

  If the upper limit is exceeded, the negative refractive power of the second lens unit L2 becomes too strong, and it becomes difficult to correct various aberrations occurring in the second lens unit L2 with a small number of lenses.

  More preferably, it is desirable to set the numerical range of conditional expression (2) as follows.

−1.20 <f2 / fw <−1.00 (2a)
In each embodiment, the above-described configuration makes it easy to correct various aberrations, has high optical performance, and achieves a zoom lens with a simple configuration while having a high zoom ratio.

  In each embodiment, it is more preferable to satisfy one or more of the following conditions.

  Let the focal length of the first lens unit L1 be f1.

  The movement amounts in the optical axis direction during zooming from the wide-angle end to the telephoto end of the first lens unit L1 and the fourth lens unit L4 are m1 and m4, respectively.

  The lens located closest to the image side of the third lens unit L3 moves in the optical axis direction during zooming from the wide-angle end to the telephoto end, and the amount of movement at this time is mr3.

At this time, 5.0 <f1 / fw <10.0 (3)
−9.5 <f1 / f2 <−5.0 (4)
−3.0 <m1 / fw <−0.5 (5)
−3.00 <m4 / fw <−1.00 (6)
−1.0 <(m4-mr3) / fw <−0.1 (7)
It is preferable to satisfy one or more of the following conditions.

  The amount of movement here refers to a change in the position of the target lens group at a specified zoom position (for example, the wide-angle end and the telephoto end) with respect to a stationary reference (for example, the imaging plane) during zooming. It does not include movements other than the specified zoom position.

  The sign of the amount of movement is positive when the change in position moves to the image side, and negative when it is opposite. The amount of movement during the reciprocating movement refers to the amount of change before and after movement.

  Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (3) relates to the ratio between the focal length of the first lens unit L1 and the focal length of the entire system at the wide-angle end, so that the entire optical system can be downsized by appropriately setting the refractive power of the first lens unit L1. The optical performance is well balanced.

  If the lower limit of conditional expression (3) is exceeded, the refractive power of the first lens unit L1 becomes too strong, so the amount of aberration generated in the first lens unit L1 increases, and the first lens unit L1 becomes one positive lens. With only the configuration, it is difficult to obtain good imaging performance.

  In addition, at the wide-angle end, the tendency of the retrofocus type refractive power arrangement, which has a negative refractive power due to the combination of the first and second lens units L1 and L2, is weakened. As a result, it becomes difficult to ensure a sufficiently long back focus.

  If the upper limit of conditional expression (3) is exceeded, the refractive power of the first lens unit L1 becomes too weak, which is advantageous for aberration correction. However, the first lens unit L1 for securing a desired zoom ratio is advantageous. This is not good because the amount of movement increases, the total lens length increases, and the front lens diameter increases.

  More preferably, it is desirable to set the numerical range of conditional expression (3) as follows.

5.4 <f1 / fw <9.8 (3a)
Conditional expression (4) relates to the ratio between the focal length of the first lens unit L1 and the focal length of the second lens unit L2, and by appropriately setting the refractive power of the first lens unit L1, the entire optical system can be reduced in size. The optical performance is well balanced.

  If the lower limit of conditional expression (4) is exceeded, the focal position on the image side of the first lens group L1 and the focal position on the object side of the second lens group L2 are too far apart, so the imaging magnification of the second lens group L2 is low. Scaling in the area.

  Therefore, the zooming efficiency at the time of zooming decreases, the amount of movement due to zooming of the first lens unit L1 increases, and the optical total length increases at the telephoto end. Alternatively, the refractive power of the second lens unit L2 becomes too strong, and various aberrations generated in the second lens unit L2 increase.

  If the upper limit is exceeded, the power (refractive power) of the first lens unit L1 becomes strong, and it is difficult to configure the first lens unit L1 with a single lens. Further, since the power of the second lens unit L2 is weakened and the zooming action is weakened, the amount of movement of the second lens unit L2 is increased and the optical system is enlarged.

  More preferably, it is desirable to set the numerical range of conditional expression (4) as follows.

−8.4 <f1 / f2 <−5.2 (4a)
Conditional expression (5) is for appropriately setting the amount of movement of the first lens unit L1 when zooming from the wide-angle end to the telephoto end.

  If the lower limit of conditional expression (5) is exceeded, the movement amount of the first lens unit L1 becomes too large, so that the total optical length increases. Further, since the variation of the chromatic aberration of magnification generated in the first lens unit L1 during zooming becomes large, correction becomes difficult.

  If the upper limit of conditional expression (5) is exceeded, the amount of movement of the first lens unit L1 becomes too small, so that the refractive power of the first lens unit must be increased in order to ensure a desired zoom ratio. As a result, the correction of various aberrations deteriorates.

  More preferably, conditional expression (5) desirably sets the numerical range of conditional expression (5) as follows.

−2.0 <m1 / fw <−1.4 (5a)
Conditional expression (6) is for appropriately setting the amount of movement of the fourth lens unit L4 when zooming from the wide-angle end to the telephoto end, and mainly reducing aberration fluctuations during zooming.

  If the lower limit of conditional expression (6) is exceeded, the amount of movement of the fourth lens unit L4 increases, and the total optical length at the telephoto end increases.

  If the upper limit is exceeded, the amount of movement of the fourth lens unit L4 becomes small, so that the refractive power of the first lens unit L1 must be increased in order to secure a desired zoom ratio. As a result, various aberrations are caused. The correction becomes worse.

  More preferably, it is desirable to set the numerical range of conditional expression (6) as follows.

-2.50 <m4 / fw <-1. 80 (6a)

Conditional expression (7) is a condition corresponding to the 3b lens component L3b of Example 4 in FIG. 7, and defines the relative movement amount of the third lens unit L3b of the third lens unit L3 and the fourth lens unit L4. is there.

  When the lower limit of conditional expression (7) is exceeded, the amount of movement of the fourth lens unit L4 becomes relatively large with respect to the third b lens component L3b, so the third b lens component L3b and the fourth lens unit L4 at the wide angle end. This is not preferable because the distance between the two becomes longer and the total length becomes too long.

  If the upper limit is exceeded, the change in the distance between the third b lens component L3b and the fourth lens unit L4 becomes small, so the sharing effect on aberration correction is weakened, and aberration fluctuations that occur during zooming are sufficiently corrected. It becomes difficult.

  In particular, the distance from the optical axis of the off-axis light beam passing through the fourth lens unit L4 is small at the wide-angle end and the telephoto end, which is disadvantageous for off-axis aberration correction in zooming.

  More preferably, it is desirable to set the numerical range of conditional expression (7) as follows.

−0.25 <(m4-mr3) / fw <−0.13 (7a)
In each embodiment, the fourth lens unit L4 may include an aspherical lens having a negative refractive power that increases from the optical axis to the periphery of the lens.

  The fourth lens unit L4 greatly moves toward the object side during zooming from the wide-angle end to the telephoto end, and the passing position of the off-axis light beam through the fourth lens unit L4 is greatly different between the wide-angle end and the telephoto end. For this reason, in the fourth lens unit L4, high optical performance is realized over the entire zoom range by disposing an aspheric surface at a position closer to the image plane side (image side surface of the negative lens).

  In addition, since the fourth lens unit L4 has a positive refractive power as a whole, it is desirable that the negative refractive power be strong from the optical axis to the periphery of the lens in order to correct various aberrations satisfactorily.

  For example, it is preferable to have a shape in which the negative refractive power of the concave surface becomes strong when it is concave, and a shape where the positive refractive power becomes weak when it is convex.

  The material of the aspherical lens is not particularly limited, but it is desirable to adopt a resin-molded one because it can be manufactured relatively easily.

  Of course, the material may be glass, or a so-called compound aspherical lens in which an aspherical resin layer is disposed on a glass substrate.

  In addition, when the zoom lens of each embodiment is applied to an interchangeable lens of a single-lens reflex camera, when using an aspherical lens made of a relatively weak resin material so as not to be damaged when handled by the user, it is most image side. It is desirable not to place it on the surface. In each embodiment, in consideration of this point, a resin aspherical lens is the second lens from the image side.

  In each embodiment, focusing is performed by moving the second lens unit L2.

  Focusing from an infinite object to a close object is performed by moving the second lens unit L2 having the strongest refractive power toward the object side in the optical axis direction. In this way, by using the so-called inner focus method, the effective lens diameter of the first lens unit L1 is reduced compared to the case where focusing is performed by the first lens unit L1.

  In each embodiment, the distance between the first lens unit L1 and the second lens unit L2 is larger at the telephoto end than the wide angle end, and the interval between the third lens unit L3 and the fourth lens unit L4 is decreased. Zooming is performed by moving the lens group.

  Therefore, if focusing is performed with the fourth lens unit L4, a space for feeding necessary for focusing must be secured in advance, and as a result, the optical total length increases.

  On the other hand, when focusing is performed with the second lens unit L2, the lens unit interval is increased as described above during zooming, so that it is easy to secure a space for feeding necessary for focusing, particularly on the telephoto side.

  In Example 4, the third lens unit L3 has a 3a lens component and a 3b lens component in order from the object side to the image side, and each lens component independently moves in the optical axis direction during zooming.

  In this way, the third-a lens component L3a and the third-b lens component L3b are independently moved in the optical axis direction during zooming, thereby facilitating correction of aberration fluctuations that occur during zooming.

  As described above, according to each embodiment, as described above, a plurality of lens groups having a predetermined refractive power are provided, and the refractive power of each lens group, a moving condition for zooming, and the like are appropriately set. As a result, the lens system is reduced in size, and a zoom lens with a zoom ratio of about 4 having good optical performance over the entire zoom range is obtained.

  In each embodiment, a converter lens system, an optical element having a small refractive power, or the like may be added to the object side of the first lens unit L1 and / or the image side of the final lens unit.

  The lens configuration of each lens group and lens component in each embodiment will be described. In the following description, it is assumed that the lens configurations are arranged in order from the object side to the image side.

  In Example 1, the first lens unit L1 includes one positive lens having a convex object-side surface. The second lens unit L2 includes a negative meniscus lens having a concave image side surface, a negative lens having both concave lens surfaces, and a positive meniscus lens having a convex object side surface.

  The third-a lens component L3a is composed of a positive lens whose both lens surfaces are convex. The third-b lens component L3b is a negative lens having a concave object-side surface. The fourth lens unit L4 includes a negative lens having a concave surface on the object side and a positive lens having convex surfaces on both lens surfaces.

  The first and second lens units L1 and L2 are the same as those in the first embodiment. The third-a lens component L3a is composed of a positive lens having convex surfaces on both lens surfaces and a negative lens having a concave surface on the object side. The third b lens component L3b and the fourth lens unit L4 are the same as those in the first embodiment.

  The first and second lens units L1 and L2 are the same as those in the first embodiment. The third-a lens component L3a is composed of a positive lens having convex surfaces on both lens surfaces and a negative lens having a concave surface on the object side. The third-b lens component L3b is a negative lens having a concave surface on the image side. The fourth lens unit L4 is the same as that in the first embodiment.

  The first and second lens units L1 and L2 are the same as those in the first embodiment. The third-a lens component L3a is composed of a positive lens having convex surfaces on both lens surfaces and a negative lens having a concave surface on the object side. The third-b lens component L3b is a negative lens having a concave surface on the image side. The fourth lens unit L4 is the same as that in the first embodiment.

  The lens configurations of the first lens unit L1 to the fourth lens unit L4 are the same as those in the first embodiment. The fifth lens unit L5 is composed of a negative lens having a concave surface on the object side.

  Next, an embodiment in which the zoom lens shown in Embodiments 1 to 5 is applied to an imaging apparatus (single-lens reflex camera) using a solid-state imaging device will be described with reference to FIG.

  FIG. 11 is a schematic diagram of a main part of a single-lens reflex camera. In FIG. 11, reference numeral 10 denotes a photographing lens having the zoom lens 1 according to the first to fifth embodiments. The zoom lens 1 is held by a lens barrel 2 that is a holding member. Reference numeral 20 denotes a camera body, which includes a quick return mirror 3 that reflects the light beam from the photographic lens 10 upward, a focusing screen 4 that is disposed in the image forming apparatus of the photographic lens 10, and an inverted image formed on the focusing screen 4. It has a penta roof prism 5 for converting to.

  Furthermore, it is composed of an eyepiece 6 for observing the erect image. Reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) for receiving an image such as a CCD sensor or a CMOS sensor or a silver salt film is disposed. At the time of photographing, the quick return mirror 3 is retracted from the optical path, and an image is formed on the photosensitive surface 7 by the photographing lens 10.

  In the following, numerical examples 1 to 5 corresponding to the first to fifth examples will be described. In each numerical example, i indicates the order from the object side, ri is the radius of curvature of each surface, di is the member thickness or air spacing between the i-th surface and the (i + 1) -th surface, and ni and νi are d Indicates the refractive index and Abbe number for the line.

When the aspherical shape is x with the displacement in the optical axis direction at the position of the height h from the optical axis as x based on the surface vertex,
X = (h ² / R) / [1+ {1- (1 + k) (h / R) ² }] ^(1/2)
+ A2h ² + A4h ⁴ + A6h ⁶ + A8h ⁸ + A10h ¹⁰ + A12h ¹²
It is represented by

  Where k is a conic constant, A2, A4, A6, A8, A10, and A12 are secondary, fourth, sixth, eighth, tenth, and twelfth aspheric coefficients, and R is a paraxial radius of curvature.

“E-0X” means “× 10 ^−x ”.

[Numerical Example 1]
Unit mm

Surface data
Surface number rd Nd νd Effective diameter

Object ∞

1 56.57689 6.9434 1.51633 64.14 52.233
2 389.6367 Variable 1 0 50.131

3 74.23163 1.4 1.712995 53.87 37.563
4 14.34295 8.52105 1 0 25.645
5 −228.44 1 1.622992 58.16 25.44
6 27.21654 0.0286 1 0 23.686
7 18.81481 2.86531 1.84666 23.93 23.518
8 28.2944 Variable 1 0 22.691

9 (Aperture) 1 1 0 11.297
10 15.49359 3.51086 1.548141 45.79 12.076
11 −38.5313 2.51184 1 0 11.922
12 −24.7552 1.2 1.84666 23.93 11.201
13 2170.501 Variable 1 0 11.294

14 −16.3192 1.5 1.58306 30.23 13.232
15 * −35.8075 0.12696 1 0 14.961
16 174.1156 5.14474 1.517417 52.43 15.846
17 −13.5748 Variable 1 0 17.142

18 Flare cut aperture 37.7227 1 0 18.08

img 0



Aspheric data
15th page
K A2 A4 A6 A8 A10 A12
0.00E + 00 0.00E + 00 9.87E−05 4.86E−07 −8.27E−09 1.25E−10 −8.78E−13


Various data
Zoom ratio 4.039467

Wide angle Medium telephoto
Focal length 15.57897 40.44766 62.93073
F number 3.58722 4.841511 5.850716
Angle of View 41.24503 18.66087 12.24687
Image height 13.66 13.66 13.66
Total lens length 116.3644 127.2444 143.5644
BF 37.7227 37.7227 37.7227


d2 2.472844 18.52879 25.82062
d8 33.21494 8.951334 3.040424
d13 5.551154 2.991125 1.880629
d17 0 21.64769 37.69727


Zoom lens group data
Group Start surface Focal length
1 1 127.285
2 3 −18.3379
3 9 47.93118
4 14 38.87


[Numerical Example 2]

Unit mm

Surface data
Surface number rd nd νd Effective diameter

Object ∞

1 56.66194 6.83785 1.51633 64.14 51.203
2 524.806 Variable 1 0 49.221

3 81.15395 1.4 1.712995 53.87 36.587
4 13.98781 8.20991 1 0 24.911
5 -155.214 1 1.622992 58.16 24.84
6 27.85823 -0.00465 1 0 23.268
7 18.93918 2.97323 1.84666 23.93 23.165
8 31.09275 Variable 1 0 22.39

9 (Aperture) 1 1 0 10.869
10 15.30927 3.52108 1.571351 52.95 11.579
11 -29.959 1.28151 1 0 11.405
12 -23.3111 1.2 1.84666 23.93 10.953
13 -123.475 0.99691 1 0 10.992

14 -155.035 1.2 1.51633 64.14 10.957
15 103.2152 Variable 1 0 10.959

16 -18.9024 1.5 1.58306 30.23 13.044
17 * -75.928 0.01641 1 0 14.704
18 61.55119 4.85924 1.531717 48.84 15.402
19 -15.2027 Variable 1 0 16.571

20 Flare cut aperture 36.12156 1 0 18.063

img 0



Aspheric data
17th page
K A2 A4 A6 A8 A10 A12
0.00E + 00 0.00E + 00 9.04E-05 3.47E-07 -8.19E-09 1.32E-10 -8.78E-13


Various data
Zoom ratio 4.009475

Wide angle Medium telephoto
Focal length 15.68876 40.49214 62.90371
F number 3.705702 4.948521 5.845604
Angle of View 41.04566 18.64179 12.25197
Image height 13.66 13.66 13.66
Total lens length 114.2333 125.1133 141.4333
BF 36.12156 36.12156 36.12156


d2 2.398707 18.77278 27.74703
d8 32.23216 8.453119 2.676942
d15 5.839385 3.238717 2.298128
d19 0 20.88564 34.94816


Zoom lens group data
Group Start surface Focal length
1 1 122.4134
2 3 -18.3161
3 9 43.1159
4 16 42.51451


[Numerical Example 3]

Unit mm

Surface data
Surface number rd nd νd Effective diameter

Object ∞

1 51.70586 5.74609 1.51633 64.14 42.439
2 1005.253 Variable 1 0 40.616

3 104.1874 1.4 1.712995 53.87 30.636
4 13.1652 6.89501 1 0 22.088
5 -76.2388 1 1.622992 58.16 22.035
6 29.15912 0.07223 1 0 21.217
7 20.24819 3.7343 1.688931 31.07 21.368
8 93.43555 Variable 1 0 20.845

9 (Aperture) 1 1 0 12.649
10 17.41558 3.87885 1.603112 60.64 13.448
11 -31.0181 3.20919 1 0 13.245
12 -17.6229 1.2 1.84666 23.93 11.901
13 -70.329 0.99759 1 0 12.084

14 170.6525 1.2 1.51633 64.14 12.119
15 83.0166 Variable 1 0 12.11

16 -28.5453 1.5 1.58306 30.23 12.174
17 * 118.6599 0.02243 1 0 13.459
18 76.42512 3.85732 1.612929 37 13.47
19 -16.7966 Variable 1 0 14.531

20 Flare cut aperture 37.76285 1 0 18.058

img 0



Aspheric data
17th page
K A2 A4 A6 A8 A10 A12
0.00E + 00 0.00E + 00 5.83E-05 9.24E-08 -5.51E-09 1.12E-10 -8.78E-13


Various data
Zoom ratio 3.924021

Wide angle Medium telephoto
Focal length 18.66231 43.79929 73.23128
F number 3.601421 4.657673 5.832695
Angle of view 36.20251 17.32151 10.56609
Image height 13.66 13.66 13.66
Total lens length 114.1577 125.0377 141.3577
BF 37.76285 37.76285 37.76285


d2 2.970986 19.00873 24.93078
d8 31.38995 10.1108 1.908764
d15 4.670867 2.640742 1.880708
d19 0 18.15153 37.51154


Zoom lens group data
Group Start surface Focal length
1 1 105.3551
2 3 -19.5617
3 9 43.01053
4 16 46.57803


[Numerical Example 4]
Unit mm

Surface data
Surface number rd nd νd Effective diameter

Object ∞

1 56.11842 7.17083 1.51633 64.14 52.619
2 466.8957 Variable 1 0 50.606

3 73.26809 1.4 1.712995 53.87 37.547
4 14.02956 8.62898 1 0 25.339
5 −148.179 1 1.622992 58.16 25.271
6 29.79651 0.00908 1 0 23.685
7 18.67054 2.83874 1.84666 23.93 23.483
8 28.15404 Variable 1 0 22.679

9 (Aperture) 1 1 0 10.966
10 14.91698 4.42485 1.595509 39.24 11.693
11 −19.8835 0.1327 1 0 11.409
12 −20.3104 1.2 1.84666 23.93 11.31
13 7216.752 Variable 1 0 11.251

14 −354.81 1.2 1.51633 64.14 11.201
15 77.11359 Variable 1 0 11.373

16 −19.2855 1.5 1.58306 30.23 13.385
17 * −108.604 0.03879 1 0 15.068
18 47.91892 5.17421 1.517417 52.43 15.852
19 −15.4213 Variable 1 0 17.02

20 Flare cut aperture 36.91461 1 0 17.928

img −65.3562



Aspheric data
17th page
K A2 A4 A6 A8 A10 A12
0.00E + 00 0.00E + 00 9.78E-05 3.70E-07 -8.54E-09 1.36E-10 -8.78E-13


Various data
Zoom ratio 4.009191

Wide angle Medium telephoto
Focal length 15.68997 40.81842 62.9041
F number 3.689203 4.964948 5.845264
Angle of View 41.04348 18.50296 12.2519
Image height 13.66 13.66 13.66
Total lens length 116.0729 126.9529 143.2729
BF 36.91461 36.91461 36.91461


d2 2.443803 18.40836 27.31302
d8 32.85312 8.713282 2.960526
d13 1.279552 1.431398 0.997136
d15 5.213661 2.800987 2.332973
d19 0 21.3161 35.38647


Zoom lens group data
Group Start surface Focal length
1 1 122.8055
2 3 −18.3018
3a 9 33.61131
3b 14 −122.569
4 16 44.42968


[Numerical Example 5]

Unit mm

Surface data
Surface number rd nd νd Effective diameter

Object ∞

1 64.25759 6.11472 1.51633 64.14 52.293
2 367.9103 Variable 1 0 50.213

3 47.97743 1.4 1.712995 53.87 36.147
4 13.39503 9.14498 1 0 24.716
5 -113.316 1 1.622992 58.16 24.503
6 28.46797 0.03789 1 0 22.892
7 18.53698 2.74794 1.84666 23.93 22.725
8 27.75913 Variable 1 0 21.921

9 (Aperture) 1 1 0 11.277
10 14.81575 3.48412 1.548141 45.79 12.114
11 -31.5232 1.80728 1 0 11.962
12 -26.8273 1.2 1.84666 23.93 11.306
13 197.6077 Variable 1 0 11.316

14 -13.7749 1.5 1.58306 30.23 12.434
15 * -28.4949 0.41069 1 0 14.143
16 344.508 5.08315 1.517417 52.43 15.305
17 -12.6001 Variable 1 0 16.572

18 -142.173 1.16304 1.603112 60.64 17.115
19 -1515.54 0 1 0 17.345
20 Flare cut aperture 38.5756 1 0 17.351

img -67.1112



Aspheric data
17th page
K A2 A4 A6 A8 A10 A12
0.00E + 00 0.00E + 00 1.25E-04 6.26E-07 -6.14E-09 8.91E-11 -8.78E-13


Various data
Zoom ratio 4.033701

Wide angle Medium telephoto
Focal length 15.60249 43.13923 62.93577
F number 3.748345 5.062077 5.662332
Angle of View 41.20219 17.57035 12.24592
Image height 13.66 13.66 13.66
Total lens length 117.2799 129.3599 147.4799
BF 38.5756 38.5756 38.5756


d2 2.371455 22.35941 36.46704
d8 33.3563 7.180538 2.911529
d13 5.232709 2.699049 2.038559
d17 0 20.80147 29.74334



Zoom lens group data
Group Start surface Focal length
1 1 149.7594
2 3 -18.2801
3 9 42.40383
4 14 38.05955
5 18 -260.219

Sectional view of the lens at the wide-angle end of Embodiment 1 of the present invention Aberration diagram of Numerical Example 1 corresponding to Example 1 of the present invention Sectional view of the lens at the wide-angle end of Embodiment 2 of the present invention Aberration diagram of Numerical Example 2 corresponding to Example 2 of the present invention Sectional view of the lens at the wide-angle end of Embodiment 3 of the present invention Aberration diagram of Numerical Example 3 corresponding to Example 3 of the present invention Cross-sectional view of a lens at a wide angle end according to Embodiment 4 of the present invention Aberration diagram of Numerical Example 4 corresponding to Example 4 of the present invention Lens cross-sectional view at the wide angle end according to Embodiment 5 of the present invention Aberration diagram of Numerical Example 5 corresponding to Example 5 of the present invention Schematic diagram of imaging device of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 L1 1st lens group 2 L2 2nd lens group 3 L3 3rd lens group 4 L3a 3a lens component 5 L3b 3b lens component 6 L4 4th lens group 7 L5 5th lens group 8 SP Aperture 9 FS Flare cut aperture 10 IP image plane 11 d d line 12 g g line 13 C. Sine condition 14 M d line meridional image plane 15 S d line sagittal image plane

Claims (12)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power are provided. ,
A zoom lens that performs zooming by moving all of the first lens group to the fourth lens group,
During zooming, the first lens unit moves to be positioned closer to the object side at the telephoto end than at the wide-angle end,
The first lens group consists of one lens,
When the focal length of the entire system at the wide angle end is fw, the focal length of the second lens group is f2, and the Abbe number of the material of at least one positive lens included in the fourth lens group is νd4,
30.0 <νd4 <60.0
−1.20 <f2 / fw <−0.80
A zoom lens characterized by satisfying the following conditions: When the focal length of the first lens group is f1,
5.0 <f1 / fw <10.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2,
−9.5 <f1 / f2 <−5.0
The zoom lens according to claim 1, wherein the following condition is satisfied. When the amount of movement in the optical axis direction during zooming from the wide-angle end to the telephoto end of the first lens group is m1, and the focal length of the entire system at the wide-angle end is fw,
−3.0 <m1 / fw <−0.5
The zoom lens according to claim 1, wherein the following condition is satisfied. When the amount of movement in the optical axis direction in zooming from the wide-angle end to the telephoto end of the fourth lens group is m4,
−3.00 <m4 / fw <−1.00
The zoom lens according to claim 1, wherein the following condition is satisfied. The lens located closest to the image side of the third lens group moves in the optical axis direction independently of the other lens groups during zooming from the wide-angle end to the telephoto end. When the amount of movement in the optical axis direction in zooming from the wide-angle end to the telephoto end of the fourth lens group is m4,
−1.0 <(m4-mr3) / fw <−0.1
The zoom lens according to claim 1, wherein the following condition is satisfied.   The zoom lens according to claim 1, wherein the fourth lens group includes an aspherical lens having a negative refractive power that increases from the optical axis to the lens periphery.   The zoom lens according to claim 1, wherein focusing is performed by moving the second lens group.   2. The third lens group has a 3a lens component and a 3b lens component in order from the object side to the image side, and each lens component independently moves in the optical axis direction during zooming. The zoom lens according to any one of 1 to 8.   In order from the object side to the image side, the third lens group includes a 3a lens component and a 3b lens component. The zoom lens according to claim 1, wherein the image is displaced in a direction perpendicular to the axis.   The zoom lens according to claim 1, wherein an image is formed on a solid-state imaging device.   An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.