JP5057898B2 - Image pickup apparatus having a zoom lens - Google Patents

Description

  The present invention relates to an image pickup apparatus including a zoom lens, and more particularly to an image pickup apparatus including a zoom lens such as a video camera or a digital camera, which is downsized.

  In recent years, digital cameras have attracted attention as next-generation cameras that replace film cameras. Furthermore, it has come to have a number of categories in a wide range from a high-function type for business use to a portable popular type.

  Portable digital cameras and video cameras of the popular type are required to reduce the depth while ensuring high image quality. The depth direction of the camera is greatly influenced by the thickness from the most object side surface of the lens system to the imaging surface. In particular, in the case of a zoom lens, the thickness tends to increase during shooting. For this reason, a so-called collapsible lens barrel that projects the zoom lens from the camera body during photographing and accommodates the zoom lens in the camera body when carried is mainly used.

As a conventional compact zoom lens, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power are so-called negative leading lenses. A type of zoom lens is known. The following documents are known as conventional examples of this type.
JP 2002-14284 A JP 2003-177315 A JP 2007-65590 A

  However, in the zoom lens of Prior Art Document 1, since the number of lenses of the first lens group having negative refractive power is two with an air interval, the thickness of the first lens group on the optical axis is large. Even if the lens barrel is retracted, the dimension of the lens barrel in the thickness direction is not sufficiently thin, which is disadvantageous for downsizing the camera.

  The zoom lens of Prior Art Document 2 is advantageous for miniaturization because the first lens group having negative refracting power is composed of one negative lens, but it is composed of only one negative lens. Astigmatism and chromatic aberration at the wide-angle end, or astigmatism and chromatic aberration at the time of zooming tend to increase, and it is difficult to increase the zoom ratio.

  The zoom lens according to Prior Art 3 has a first lens unit having negative refractive power as one lens component having a negative lens and a positive lens (the lens component has an entrance surface and an exit surface on the optical axis that are in contact with air) This is advantageous for miniaturization and reduction of the chromatic aberration of the first lens group, but it is difficult to suppress fluctuations such as astigmatism, and the angle of view and brightness. It will be disadvantageous to secure.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image pickup apparatus having a zoom lens that is advantageous for downsizing at the time of retracting and easily secures optical performance even when a zoom ratio, brightness, and angle of view are secured. It is intended.

An imaging apparatus according to an embodiment of the present invention includes:
A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an image formed by the zoom lens into an electrical signal;
The zoom lens
From the object side,
A first lens group having negative refractive power;
A second lens group having positive refractive power;
A third lens group having negative refractive power;
It consists of a fourth lens group with positive refractive power ,
When a lens block having only two surfaces on the optical axis that are in contact with air, the entrance surface and the exit surface, is defined as a lens component,
The first lens group is composed of one negative lens component in which one negative lens and one positive lens are cemented,
When zooming from the wide-angle end to the telephoto end,
An interval between the first lens group and the second lens group is narrowed,
The interval between the second lens group and the third lens group changes,
The distance between the third lens group and the fourth lens group changes,
The following conditions are satisfied.
-1.2 <Hf2 / Y <-0.7 (1)
30 <(νdL1n−νdL1p) <50 (3)
However,
Hf2 is the distance from the object-side lens surface of the second lens group on the optical axis to the front principal point of the second lens group,
The sign is a negative sign when the front principal point is closer to the object side than the second lens group,
Y is the maximum image height within the possible effective imaging area
νdL1n is the Abbe number of the negative lens in the first lens group,
νdL1p is the Abbe number of the positive lens in the first lens group,
It is.
Furthermore, an imaging apparatus according to another embodiment of the present invention includes:
A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an image formed by the zoom lens into an electrical signal;
The zoom lens
From the object side,
A first lens group having negative refractive power;
A second lens group having positive refractive power;
A third lens group having negative refractive power;
It consists of a fourth lens group with positive refractive power,
When a lens block having only two surfaces on the optical axis that are in contact with air, the entrance surface and the exit surface, is defined as a lens component,
The first lens group is composed of one negative lens component in which one negative lens and one positive lens are cemented,
The second lens group includes one positive lens and one negative lens in order from the object side.
When zooming from the wide-angle end to the telephoto end,
An interval between the first lens group and the second lens group is narrowed,
The interval between the second lens group and the third lens group changes,
The distance between the third lens group and the fourth lens group changes,
The second lens group satisfies the following conditions:
It is characterized by that.
-1.2 <Hf2 / Y <-0.7 (1)
However,
Hf2 is the distance from the object-side lens surface of the second lens group on the optical axis to the front principal point of the second lens group,
The sign is a negative sign when the front principal point is closer to the object side than the second lens group,
Y is the maximum image height within the possible effective imaging area
It is.

  In this manner, disposing the lens unit having a negative refractive power on the object side is advantageous in reducing the size of the zoom lens in the radial direction and downsizing. The second lens group has a zooming function by narrowing the distance between the first lens group and the second lens group.

  In the case of such a zoom lens, the thickness of the first lens group on the optical axis is configured by configuring the first lens group with one negative lens component obtained by cementing one negative lens and one positive lens. And the occurrence of chromatic aberration in the first lens group can be easily suppressed. On the other hand, since the negative lens and the positive lens are in contact with each other, it is difficult to correct astigmatism.

  For this reason, the third lens group having negative refractive power is arranged on the image side of the second lens group having positive refractive power, and the distance between the front and rear of the third lens group is moved to change the astigmatism variation by adjusting the Petzval sum. It becomes easy to correct and correct various aberrations such as chromatic aberration.

  The fourth lens group having positive refracting power is disposed on the image side of the third lens group having negative refracting power, thereby providing a function of separating the exit pupil from the image plane.

  Thus, by devising the configuration of the first lens group, the arrangement of the refractive power of the lens group, and the movement method, the imaging apparatus is equipped with a zoom lens that is small but easily suppresses aberration fluctuations.

  On the other hand, if the first lens group is composed of one negative lens component, the rear principal point position of the first lens group is located almost in the middle of the first lens group, so that the zoom ratio is ensured and the size is reduced. In order to achieve both compatibility, it is preferable that the front principal point of the second lens group is put forward to satisfy the following conditional expression (1).

-1.2 <Hf2 / Y <-0.7 (1)
However, Hf2 is the distance from the object side lens surface of the second lens group on the optical axis to the front principal point of the second lens group,
The sign is a negative sign when the front principal point is closer to the object side than the second lens group,
Y is the maximum image height within a possible effective imaging region.

  Conditional expression (1) specifies a preferred principal point position of the second lens group, and is intended to make it easy to suppress the amount of movement while ensuring the zooming function of the second lens group.

  By appropriately projecting the front principal point position of the second lens group responsible for the zooming function toward the object side (front side), the magnification sharing by the second lens group without increasing the distance between the first and second lens groups at the wide angle end Is easy to secure, which is advantageous for shortening the overall length of the zoom lens.

  By making sure that the upper limit of conditional expression (1) is not exceeded, the principal point position is made closer to the object side, which is advantageous in reducing the size and thickness of the zoom lens. Further, by making sure that the lower limit of conditional expression (1) is not exceeded, it is possible to prevent the principal point from going too far toward the object side, and to easily suppress performance deterioration due to eccentricity.

  Moreover, it is more preferable that the lower limit value of the conditional expression (1) is −1.0. Furthermore, it is more preferable that the upper limit value of conditional expression (1) is −0.75.

  Furthermore, it is more preferable to satisfy any one or more of the following configurations in terms of size reduction, high performance, and cost reduction.

  It is preferable that the following conditional expression (2) is satisfied.

0.1 <ΣG1d / fw <0.25 (2)
Where ΣG1d is the thickness of the first lens group on the optical axis,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is.

  Conditional expression (2) specifies the preferred thickness of the first lens group. By making sure that the lower limit of conditional expression (2) is not exceeded, it is advantageous for securing the axial thickness of the positive lens in the first lens group and the edge thickness of the negative lens, and ensuring the refractive power of each lens. It becomes easy and it becomes advantageous for aberration reduction. By making sure that the upper limit of conditional expression (2) is not exceeded, it is advantageous for downsizing the zoom lens when the first lens unit is retracted.

  Moreover, it is more preferable that the lower limit value of conditional expression (2) is 0.12. Furthermore, it is more preferable that the upper limit value of conditional expression (2) is 0.22.

  Furthermore, it is preferable that the most image side lens surface of the first lens unit is a concave surface, and the lens surface is an aspherical surface. Such a configuration is effective for correcting astigmatism and coma in the first lens group.

  In addition, it is preferable that the lens surface closest to the object side of the first lens group is a concave surface, and that the negative refracting power decreases as the lens surface moves away from the optical axis. With this configuration, it is easy to secure the negative refractive power of the first lens unit, which is advantageous for correcting the axial aberration on the telephoto side. Further, the aspherical surface can reduce the amount of peripheral protrusion on the concave surface on the object side, which is advantageous for downsizing and thinning, and also for reducing distortion on the wide angle side.

  The material of the positive lens of the first lens group is preferably resin. Further, the positive lens material of the first lens group is preferably an energy curable resin, and the negative lens component of the first lens group is preferably a positive lens molded directly on the lens surface of the negative lens. .

  If the optical material of the positive lens of the first lens group is an organic material such as a resin, or an optical material whose optical characteristics are changed by diffusing inorganic fine particles in the organic material, thin lens processing becomes easy. And in order to process as thin as possible, the method of forming a cemented lens by a method of directly molding into a negative lens using an energy curable resin such as an ultraviolet curable resin, when the cemented surface is aspherical, Manufacturing is easier.

  Moreover, it is preferable that the cemented surface of the positive lens and the negative lens in the first lens group is an aspherical surface. In addition, by making the cemented surface of the positive lens and the negative lens aspherical, it is possible to satisfactorily correct the amount of astigmatism and chromatic aberration that occur in the first lens group during zooming. If the positive lens is molded from resin, such an aspherical joining surface can be easily manufactured.

  Moreover, it is preferable that the following conditional expression (3) is satisfied.

30 <(νdL1n−νdL1p) <50 (3)
Where νdL1n is the Abbe number of the negative lens in the first lens group,
νdL1p is the Abbe number of the positive lens in the first lens group,
It is.

  Conditional expression (3) specifies a preferable material of the first lens group. By making sure that the lower limit of conditional expression (3) is not exceeded, it becomes easier to correct the chromatic aberration of the first lens group. By making sure that the upper limit of conditional expression (3) is not exceeded, it is advantageous in terms of the availability and productivity of a combination of positive and negative lens materials.

  Further, it is more preferable that the lower limit value of conditional expression (3) is 33. Furthermore, it is more preferable that the upper limit of conditional expression (3) is 40.

  In addition, the second lens group preferably includes, in order from the object side, a positive lens component having a positive refractive power and a negative lens component having a negative refractive power. The minimum number of lens components that can suppress various aberrations such as spherical aberration, chromatic aberration, astigmatism, and coma generated in the second lens group is advantageous for downsizing and thinning.

  Furthermore, the front principal point position can be made to be the object of the second lens group by making the configuration of the second lens group a lens unit having a positive refractive power and a lens unit having a negative refractive power in order from the object side, By bringing the principal point close to the first lens group at the telephoto end, it is advantageous for securing a zooming load with respect to the movement amount of the second lens group.

  The second lens group preferably includes a first positive lens, a cemented lens of a second positive lens, and a negative lens in order from the object side. Since the second lens group is a lens group mainly responsible for zooming, it is better to correct aberrations in the second lens group well in order to ensure higher optical performance. Therefore, the configuration of the second lens group may include two positive lenses and one negative lens, and sufficiently correct various aberrations such as spherical aberration, astigmatism, and coma. preferable. In addition, the configuration having a cemented lens is effective in correcting axial chromatic aberration and lateral chromatic aberration.

  Furthermore, the configuration of the second lens group is a first positive lens and a cemented lens of a second positive lens and a negative lens in order from the object side, which is advantageous for bringing the front principal point position ahead of the second lens group. is there.

  In addition, the second lens group may be configured by one positive lens and one negative lens in order from the object side. With this configuration, it is easy to correct spherical aberration, astigmatism, chromatic aberration, coma, etc. while suppressing the thickness of the second lens group on the optical axis, and the principal point is located closer to the object side. It is easy to secure the zoom ratio.

  Furthermore, in this case, if the second lens group is a biconvex positive lens and a negative meniscus lens having a convex surface facing the object side, it is more advantageous for reducing aberration and securing a zoom ratio while ensuring positive refractive power. It becomes.

  Furthermore, it is preferable that the following conditional expression is satisfied.

ndL2p> 1.65 (4A)
νdL2p> 40.0 (4B)
νdL2n <30.0 (4C)
Where ndL2p is the refractive index of the d-line of the positive lens in the second lens group νdL2p is the Abbe number of the positive lens in the second lens group,
νdL2n is the Abbe number of the negative lens in the second lens group,
It is.

  By preventing the positive lens of the second lens group from falling below the lower limit of conditional expression (4A), it becomes easy to suppress the occurrence of astigmatism in the third lens group. Further, the positive lens of the second lens group does not fall below the lower limit of the conditional expression (4B), and the negative lens does not exceed the upper limit of the conditional expression (4C). This is advantageous for correcting chromatic aberration and lateral chromatic aberration.

  Further, it is more preferable that the lower limit value of conditional expression (4A) is 1.68. Furthermore, the upper limit value of conditional expression (4A) is a manufacturable lens material. However, if the upper limit value is set to 2.2 or less, the manufacturing error of the surface shape is easily reduced.

  Further, it is more preferable that the lower limit value of the conditional expression (4B) is 45. Further, the upper limit value of conditional expression (4B) is a manufacturable lens material. However, if the upper limit value is set to 75 or less, the influence of the anomalous dispersion of the material can be easily suppressed.

  Further, it is more preferable that the upper limit value of conditional expression (4C) is 25. Further, the lower limit value of the conditional expression (4C) is a manufacturable lens material. However, if the lower limit value is set to 17 or more, the material can be easily obtained.

  In addition, it is preferable that the most object side lens surface of the second lens group is an aspherical surface. Since the axial light beam diverges and enters on the most object side surface of the second lens group, the aspherical surface is effective in correcting spherical aberration.

  If the aspherical surface has a shape in which the positive refractive power decreases as it moves away from the optical axis, it is effective to easily reduce the size of the second lens group while suppressing the occurrence of spherical aberration.

  The third lens group is preferably composed of one negative lens. It is possible to correct a practical aberration level with a minimum configuration, which is advantageous for downsizing and thinning.

  Furthermore, it is preferable that the negative lens in the third lens group has at least one aspheric surface. The aspheric surface is preferably a lens surface on the image plane side of the negative lens. The negative lens of the third lens group is provided with an aspherical surface because the difference in the height of the off-axis chief ray that passes through the outermost side at the wide-angle end and the off-axis chief ray that passes through the outermost side at the telephoto end tends to increase. This is advantageous in adjusting the amount of astigmatism and distortion variation during zooming. Furthermore, since the height from the optical axis on which the off-axis chief ray is incident is higher on the image side surface than on the object side surface of the negative lens, aberration variation can be adjusted more effectively.

  Further, the negative lens in the third lens group is preferably made of resin. A practical aberration level can be corrected even with a resin material, which contributes to a reduction in the cost of the zoom lens. Further, it is preferable to process aspherical surfaces.

  Moreover, it is preferable that the following conditional expression (5) is satisfied.

2.2 <{β2 (t) / β2 (w)} / {β3 (t) / β3 (w)} <3.0
... (5)
Where β2 (t) is the lateral magnification at the telephoto end of the second lens group,
β2 (w) is the lateral magnification at the wide-angle end of the second lens group,
β3 (t) is the lateral magnification at the telephoto end of the third lens group,
β3 (w) is the lateral magnification at the wide-angle end of the third lens group,
It is.

  Conditional expression (5) specifies a preferable zooming contribution ratio of the second lens group and the third lens group. By making sure that the lower limit of conditional expression (5) is not exceeded, the variable power contribution of the third lens group is moderately suppressed, and it becomes easier to obtain the field curvature correction effect. Further, by making sure that the upper limit of conditional expression (5) is not exceeded, the zooming contribution of the second lens group is moderately suppressed, and the effect of performance degradation due to assembly errors of the second lens group can be easily reduced. Alternatively, the contribution of zooming of the third lens group is secured, which is advantageous for securing the zooming ratio.

  Further, it is more preferable that the lower limit value of conditional expression (5) is 2.4. Furthermore, it is more preferable that the upper limit value of conditional expression (5) is 2.8.

  The fourth lens group is preferably composed of one positive lens. A practical aberration level can be corrected with the minimum number of constituent lenses, which is advantageous for downsizing and thinning.

  Furthermore, it is preferable that the positive lens in the fourth lens group has at least one aspheric surface. In that case, the aspherical surface is preferably a lens surface on the image plane side of the positive lens. The positive lens in the fourth lens group has an aspherical surface because there is a large difference in height between the off-axis chief ray that passes through the outermost side at the wide-angle end and the off-axis chief ray that passes through the outermost side at the telephoto end. It is effective in suppressing the amount of astigmatism and distortion variation during zooming. Furthermore, since the height of the off-axis principal ray is higher on the image side surface than on the object side, it is more effective.

  In addition, the positive lens in the fourth lens group is preferably made of resin. A practical aberration level can be corrected even with a resin material, which contributes to a reduction in the cost of the zoom lens. It is also easy to form an aspherical surface.

  The fourth lens group is preferably positioned on the image side at the telephoto end rather than at the wide angle end. The fourth lens group can also have a multiplying action, which is more advantageous for securing a zoom ratio.

  Further, it is preferable that an aperture stop is disposed between the object side space and the image side space of the second lens group, and the brightness stop moves together with the second lens group. This makes it easy to reduce the size of the second lens group even if the second lens group has a main zooming function, which is advantageous for downsizing when retracted and for reducing aberrations in the second lens group.

  Furthermore, it is preferable to move the first, second, third, and fourth lens groups as follows. Upon zooming from the wide-angle end to the telephoto end, the first lens unit moves to the image plane side and then moves to the object side with the moving direction reversed, the second lens unit moves to the object side, and the third lens unit It is preferable that the distance from the second lens group is wider at the telephoto end than at the wide-angle end, and the fourth lens group is moved toward the image plane at the telephoto end than at the wide-angle end.

  By moving the first lens group to the image plane side first on the wide angle side, the second lens group can have a zooming function even if the amount of movement of the second lens group to the object side is reduced. At this time, the fluctuation of the exit pupil on the wide angle side can be reduced, the fluctuation of the incident height of the light beam to the third lens group can be easily suppressed, and the correction of the off-axis aberration can be facilitated. On the telephoto side, the first lens group moves to the object side, so that a space for moving the second lens group is secured, which is more advantageous for securing a zoom ratio.

  Further, the movement of the fourth lens group places a burden on the fourth lens group on the magnification, which is advantageous for achieving a high zoom ratio while suppressing fluctuations in aberrations. In addition, by moving the third lens group at the time of zooming, the position of the off-axis light beam incident on the third lens group is adjusted, which is advantageous for reducing the variation in field curvature.

  Furthermore, it is more preferable to move the first, second, third, and fourth lens groups so as to satisfy the following conditions. When any zoom state in which the focal length of the entire zoom lens system is 0.9 × √ (fw · ft) to 1.05 × √ (fw · ft) is set to the middle zoom state, any intermediate In the near zoom state, it is preferable that the first lens group, the second lens group, the third lens group, and the fourth lens group satisfy the following conditional expressions.

−0.6 <Δ1GWS / fw <−0.1 (6)
-4.0 <Δ1GWS / Δ1GST <−0.25 (7)
0.3 <Δ2GWS / Δ2GST <0.95 (8)
-20.0 <Δ3GWS / Δ3GST <0.5 (9)
-0.5 <Δ4GST / Δ4GWS <1.5 (10)
However, Δ1GWS is the difference in position in the middle zoom state with respect to the position of the first lens group at the wide-angle end,
Δ2GWS is the difference between the position of the second lens group in the middle zoom state with respect to the position at the wide-angle end,
Δ3GWS is the difference in position in the middle zoom state with respect to the position of the third lens group at the wide-angle end,
Δ4GWS is the difference in position in the middle zoom state with respect to the position of the fourth lens group at the wide-angle end,
Δ1GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the first lens group,
Δ2GST is the difference in the position at the telephoto end with respect to the position in the middle zoom state of the second lens group,
Δ3GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the third lens group,
Δ4GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the fourth lens group,
The sign is a positive sign for the direction to the object side, a negative sign for the direction to the image side,
Δ3GST is a positive value,
Δ4GWS is a negative value,
fw is the focal length of the zoom lens at the wide angle end.

  Conditional expression (6) specifies a preferable movement of the first lens group. The amount of movement of the first lens unit toward the image side is not excessively increased so as not to fall below the lower limit of conditional expression (6), and the overall length at the wide angle end is reduced in the radial direction of the first lens unit. This is advantageous for downsizing. Ensuring that the amount of movement of the first lens unit toward the image side is ensured so as not to exceed the upper limit of conditional expression (6), and that the magnification burden for the amount of movement of the second lens unit on the wide-angle side is ensured. It is preferable in terms of securing the ratio and reducing aberration fluctuations.

  Further, it is more preferable that the lower limit value of the conditional expression (6) is −0.5, and further −0.4. Furthermore, it is more preferable that the upper limit value of the conditional expression (6) is −0.15, more preferably −0.2.

  Conditional expression (7) specifies a preferable movement of the first lens group. From the viewpoint of miniaturization, it is preferable to suppress the total length at the wide-angle end so as not to fall below the lower limit of the conditional expression (7). In view of miniaturization, it is preferable to suppress the total length at the telephoto end so as not to exceed the upper limit of the conditional expression (7).

  Further, it is more preferable that the lower limit value of the conditional expression (7) is −3.0, more preferably −2.5. Furthermore, it is more preferable that the upper limit value of the conditional expression (7) is −0.33, more preferably −0.4.

  Conditional expression (8) specifies a preferable movement of the second lens group. The amount of movement of the second lens unit on the wide angle side is appropriately secured so as not to fall below the lower limit of conditional expression (8), and the function of securing the zoom ratio and correcting the field curvature of the third lens unit is ensured. It is preferable to make it easy. The amount of movement of the second lens unit on the wide-angle side is prevented from becoming too large so as not to exceed the upper limit of conditional expression (8), and fluctuations in the position where off-axis rays enter the third lens unit are suppressed. Is preferable for aberration correction.

  Further, it is more preferable that the lower limit value of the conditional expression (8) is 0.4, further 0.5. Furthermore, it is more preferable that the upper limit value of conditional expression (8) is 0.90, further 0.80.

  Conditional expression (9) specifies a preferable movement of the third lens group. In order to correct curvature of field, it is preferable that conditional expression (9) does not fall below the lower limit so that the third lens unit does not move too far to the image side on the wide angle side. Further, when the fourth lens group is extended during focusing, it is easy to secure the moving space, which is preferable. Alternatively, it is easy to reduce the effective diameter of the fourth lens group on the telephoto side, which is preferable in terms of miniaturization. It is preferable that the function of correcting the curvature of field of the third lens group is secured by making sure that the upper limit of conditional expression (9) is not exceeded.

  Further, it is more preferable that the lower limit value of the conditional expression (9) is −10.0, further −5.0, and further −3.0. Furthermore, it is more preferable that the upper limit value of conditional expression (9) is 0.2, further 0, and further −0.03.

Conditional expression (10) specifies a preferable movement of the fourth lens group. By setting the conditional expression (10) within the lower and upper limits, it is advantageous for securing a zoom ratio while suppressing aberration fluctuations by moving the fourth lens group on the wide angle side. In addition, by making sure that the lower limit of conditional expression (10) is not exceeded, it becomes easier to secure the variable magnification burden of the fourth lens group, which is advantageous for increasing the variable magnification ratio. Avoiding exceeding the upper limit of conditional expression (10) is advantageous for shortening the overall length at the wide-angle end. Further, the lower limit value of conditional expression (10) is −0.3, further −0.2, Furthermore, it is more preferable to set it to -0.15. Furthermore, it is more preferable that the upper limit value of conditional expression (10) is 1.0, further 0.85, and further 0.7.

  Further, the imaging apparatus may include an image processing unit that performs signal processing for correcting aberration included in the electrical signal. Allowing the aberration of the zoom lens is advantageous for further miniaturization and the like.

  When the zoom lens has a focusing function, each conditional expression described above is configured in a state in which it is focused at the farthest distance.

  Focusing from a long distance object to a short distance object may be performed by extending the first lens group, extending the entire zoom lens, moving the second lens group, the third lens group, and the fourth lens group. In order to easily reduce the driving load, it is preferable to perform focusing with a third lens group with negative refractive power or a fourth lens group with positive refractive power.

  A compact image pickup apparatus having a zoom lens that is advantageous for downsizing at the time of collapse and that can easily ensure optical performance even when the zoom ratio, brightness, and angle of view are secured can be provided.

  In each of the embodiments described below, the first lens group having a negative refracting power is a zoom lens having a large zoom ratio of about 3 times and an angle of view of about 60 ° at the wide-angle end and a high wide-angle imaging performance. A compact zoom lens that realizes a compact size when the lens barrel is retracted. In addition, the zoom lens is an inexpensive zoom lens suitable for an electronic image sensor such as a CCD or CMOS.

  In Examples 1 to 6, the second lens group has a configuration of a positive lens and a cemented lens of a positive lens and a negative lens in order from the object side. In Examples 7 to 11, the second lens group is in order from the object side. The configuration is a positive lens and a negative lens.

  In Examples 1 to 11, the third lens group is made of a resin material.

  Further, in Examples 1, 4, 6, 10, and 11, the fourth lens group is made of a glass material, and in Examples 2, 3, 5, 7, and 9, the fourth lens group is made of a resin material. Yes.

  In Examples 1, 2, 3, 10, and 11, the cemented surface of the negative lens and the positive lens in the first lens group is aspheric.

  Regarding the movement of the first lens group, in each embodiment, the zoom lens moves to the object side after moving to the image side at the time of zooming from the wide angle end to the telephoto end. Examples 1 to 9 are located closer to the image side at the telephoto end than at the wide-angle end. Examples 10 and 11 are located closer to the object side at the telephoto end than at the wide-angle end.

  Regarding the movement of the second lens group, in each embodiment, it moves only to the object side at the time of zooming from the wide-angle end to the telephoto end.

  Regarding the movement of the third lens group, it moves to the object side after moving to the image side in each embodiment. The state in which the third lens group is located closest to the image side is different in each example, and Examples in which the second figure from the top is located closest to the image side are Examples 1, 8, 9, 10, Examples in which the third figure from the top is located closest to the image side are Embodiments 2, 3, 4, 5, 7, and 11, and the fourth figure from the top is the condition located closest to the image side. An example is Example 6. Examples 2, 3, and 6 are located closer to the image side at the telephoto end than at the wide-angle end. Examples 1, 4, 5, 7, 8, 9, 10, and 11 are located closer to the object side at the telephoto end than at the wide-angle end.

  Regarding the movement of the fourth lens group, it is positioned closer to the image side at the telephoto end than at the wide-angle end in each embodiment. Examples 1, 4, 6, 10, and 11 move only to the image side. Examples 2, 3, 5, 7, 8, and 9 move to the image side and then move to the object side.

  In the first to eleventh embodiments, the effective imaging area is rectangular and constant in the full zoom state. The value corresponding to the conditional expression in each embodiment is a value in a state where an object point at infinity is in focus. The total length is the back focus added to the distance on the optical axis from the entrance surface to the exit surface of the zoom lens. The back focus is indicated by the air equivalent length.

  Examples 1 to 11 of the zoom lens according to the present invention will be described below. The wide-angle end (a), the wide-angle side changing point (b), the intermediate state (the state in which the first lens unit is located closest to the image side) (c), and the telephoto side Lens cross-sectional views at the changing point (d) and the telephoto end (e) are shown in FIGS. In each figure, the first lens group is G1, the second lens group is G2, the aperture stop is S, the third lens group is G3, the fourth lens group is G4, the optical low-pass filter is F, and the CCD is an electronic image sensor. The cover glass is indicated by C, and the image plane of the CCD is indicated by I. As for the near-infrared sharp cut coat, for example, the optical low-pass filter F may be directly coated, or an infrared cut absorption filter may be separately arranged.

  As shown in FIG. 1, the zoom lens according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below. Here, the point at which the movement direction of the second lens group G2 or the fourth lens group G4 changes between the wide-angle end and the intermediate state is taken as the wide-angle side change point, and the second lens group between the intermediate state and the telephoto end. The point at which the moving direction of G2 or the fourth lens group G4 changes was taken as the telephoto side change point. same as below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the wide-angle side changing point, moves to the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the wide-angle side changing point. It moves to the object side while widening the distance between the second lens group G2 and the fourth lens group G4 to the telephoto end, and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located slightly closer to the object side than the wide-angle end.

  The fourth lens group G4 narrows the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and widens the distance from the third lens group G3 from the wide-angle side changing point to the telephoto end. Move to. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a biconvex positive lens, and the second lens group G2 includes a biconvex positive lens and a positive meniscus lens having a convex surface facing the object side. And a cemented lens of a negative meniscus lens having a convex surface facing the object side, the third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is a biconvex positive lens. Consists of a single lens.

  The aspherical surfaces are the entire surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the negative meniscus lens of the third lens group G3, and both of the fourth lens group G4. It is used for 7 surfaces on the image side of the convex positive lens.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves to the image side from the wide-angle end to the wide-angle side changing point while increasing the distance between the second lens group G2 and the fourth lens group G4, and from the wide-angle side changing point to the intermediate state. The distance between the second lens group G2 and the fourth lens group G4 is increased, and the distance between the second lens group G2 and the fourth lens group G4 is decreased. Move to the object side while widening the distance, widen the distance from the second lens group G2 from the telephoto side change point to the telephoto end, move to the object side while narrowing the distance from the fourth lens group G4, and from the wide angle end Move to the telephoto end with a concave locus on the object side. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The fourth lens group G4 widens the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and narrows the distance from the third lens group G3 from the wide-angle side changing point to the intermediate state. Moves to the image side while widening the distance from the third lens group G3 to the telephoto side change point, and moves to the object side from the telephoto side change point to the telephoto end while narrowing the distance to the third lens group G3. Move from the end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and a fourth lens group. G4 includes one biconvex positive lens.

  The aspherical surfaces are the entire surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the negative meniscus lens of the third lens group G3, and both of the fourth lens group G4. It is used for 7 surfaces on the image side of the convex positive lens.

  As shown in FIG. 3, the zoom lens of Example 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves to the image side from the wide-angle end to the wide-angle side changing point while increasing the distance between the second lens group G2 and the fourth lens group G4, and from the wide-angle side changing point to the intermediate state. The distance between the second lens group G2 and the fourth lens group G4 is increased from the intermediate state to the telephoto end while increasing the distance between the second lens group G2 and the distance between the second lens group G4 and the fourth lens group G4. It moves to the object side while spreading and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The fourth lens group G4 widens the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and narrows the distance from the third lens group G3 from the wide-angle side changing point to the intermediate state. Moves to the image side while increasing the distance from the third lens group G3 to the telephoto side change point, and moves to the object side while increasing the distance from the third lens group G3 from the telephoto side change point to the telephoto end. Move from the end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and a fourth lens group. G4 includes one biconvex positive lens.

  The aspherical surfaces are the entire surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the negative meniscus lens of the third lens group G3, and both of the fourth lens group G4. It is used for 7 surfaces on the image side of the convex positive lens.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves to the image side from the wide-angle end to the wide-angle side changing point while increasing the distance between the second lens group G2 and the fourth lens group G4, and from the wide-angle side changing point to the intermediate state. The distance between the second lens group G2 and the fourth lens group G4 is increased from the intermediate state to the telephoto end while increasing the distance between the second lens group G2 and the distance between the second lens group G4 and the fourth lens group G4. It moves to the object side while spreading and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 widens the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and narrows the distance from the third lens group G3 from the wide-angle side changing point to the intermediate state. Moves to the image side while increasing the distance from the third lens group G3 to the telephoto end. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and a fourth lens group. G4 includes one biconvex positive lens.

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 6 surfaces of the image side surface of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is located closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves to the image side from the wide-angle end to the wide-angle side changing point while increasing the distance between the second lens group G2 and the fourth lens group G4, and from the wide-angle side changing point to the intermediate state. The distance between the second lens group G2 and the fourth lens group G4 is increased from the intermediate state to the telephoto end while increasing the distance between the second lens group G2 and the distance between the second lens group G4 and the fourth lens group G4. It moves to the object side while spreading and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The fourth lens group G4 widens the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and narrows the distance from the third lens group G3 from the wide-angle side changing point to the intermediate state. Moves to the image side while increasing the distance from the third lens group G3 to the telephoto side change point, and moves to the object side while increasing the distance from the third lens group G3 from the telephoto side change point to the telephoto end. Move from the end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and a fourth lens group. G4 includes one biconvex positive lens.

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 6 surfaces of the image side surface of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 6, the zoom lens of Embodiment 6 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the wide-angle side changing point, moves to the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the wide-angle side changing point The second lens group G2 and the fourth lens group G4 move to the image side while increasing the distance between the second lens group G2 and the fourth lens group G4 up to the telephoto side change point, and move from the telephoto side change point to the telephoto end. It moves to the object side while widening the distance from the object, and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the image side than the wide-angle end.

  The fourth lens group G4 narrows the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and widens the distance from the third lens group G3 from the wide-angle side changing point to the telephoto end. Moving. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a biconvex positive lens. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is composed of one biconvex positive lens.

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 6 surfaces of the image side surface of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 7, the zoom lens according to the seventh embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves to the image side from the wide-angle end to the wide-angle side changing point while increasing the distance between the second lens group G2 and the fourth lens group G4, and from the wide-angle side changing point to the intermediate state. The distance between the second lens group G2 and the fourth lens group G4 is increased from the intermediate state to the telephoto end while increasing the distance between the second lens group G2 and the distance between the second lens group G4 and the fourth lens group G4. It moves to the object side while spreading and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 widens the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and narrows the distance from the third lens group G3 from the wide-angle side changing point to the intermediate state. Moves to the image side while increasing the distance from the third lens group G3 to the telephoto side change point, and moves to the object side while increasing the distance from the third lens group G3 from the telephoto side change point to the telephoto end. Move from the end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is composed of one biconvex positive lens.

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 6 surfaces of the image side surface of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 8, the zoom lens according to the eighth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the wide-angle side changing point, moves to the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the wide-angle side changing point. It moves to the object side while widening the distance between the second lens group G2 and the fourth lens group G4 to the telephoto end, and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 narrows the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and widens the distance from the third lens group G3 from the wide-angle side changing point to the telephoto side changing point. Moving from the telephoto side changing point to the telephoto end, moving toward the object side while increasing the distance from the third lens group G3, and moving from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is a positive meniscus lens 1 having a convex surface facing the image side. It consists of sheets.

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 6 surfaces of the image side surface of the positive meniscus lens of the fourth lens group G4.

  As shown in FIG. 9, the zoom lens according to the ninth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the wide-angle side changing point, moves to the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the wide-angle side changing point. It moves to the object side while widening the distance between the second lens group G2 and the fourth lens group G4 to the telephoto end, and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 narrows the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and widens the distance from the third lens group G3 from the wide-angle side changing point to the telephoto side changing point. Moving from the telephoto side changing point to the telephoto end, moving toward the object side while increasing the distance from the third lens group G3, and moving from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is composed of one biconvex positive lens on the image side. .

  The aspherical surfaces are the most object side surface and the most image side surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the negative meniscus lens of the third lens group G3. And 7 surfaces on both sides of the biconvex positive lens of the fourth lens group G4.

  As shown in FIG. 10, the zoom lens of Example 10 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is slightly closer to the image side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the wide-angle side changing point, moves to the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the wide-angle side changing point. It moves to the object side while widening the distance between the second lens group G2 and the fourth lens group G4 to the telephoto end, and moves from the wide-angle end to the telephoto end with a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 narrows the distance from the third lens group G3 from the wide-angle end to the wide-angle side changing point, and widens the distance from the third lens group G3 from the wide-angle side changing point to the telephoto end. Moving. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is composed of one biconvex positive lens.

  The aspherical surfaces are the entire surface of the cemented lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the negative meniscus lens of the third lens group G3, and both of the fourth lens group G4. It is used for 7 surfaces on the image side of the convex positive lens.

  As shown in FIG. 11, the zoom lens of Example 11 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power. The lens unit G3 includes a fourth lens unit G4 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the image side from the wide-angle end to the intermediate state, moves toward the object side from the intermediate state to the telephoto end, and moves along a concave locus on the object side from the wide-angle end to the telephoto end. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The aperture stop S and the second lens group G2 move integrally from the wide-angle end to the telephoto end while narrowing the distance from the first lens group G1 and widening the distance from the third lens group G3. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 moves from the wide-angle end to the intermediate state, moves toward the image side while increasing the distance from the second lens group G2 and narrows the distance from the fourth lens group G4, and from the intermediate state to the telephoto end. It moves toward the object side while increasing the distance between the second lens group G2 and the fourth lens group G4, and moves from the wide-angle end to the telephoto end while drawing a concave locus on the object side. At the telephoto end, it is located closer to the object side than the wide-angle end.

  The fourth lens group G4 moves toward the image side while narrowing the distance from the third lens group G3 from the wide-angle end to the intermediate state and widening the distance from the third lens group G3 from the intermediate state to the telephoto end. At the telephoto end, it is positioned closer to the image side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of a biconcave negative lens and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one negative meniscus lens having a convex surface facing the object side, and the fourth lens group G4 is a positive meniscus lens 1 having a convex surface facing the image side. It consists of sheets.

  The aspheric surfaces are the entire surface of the cemented lens of the first lens group G1, the both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the negative meniscus lens of the third lens group G3, and the positive surface of the fourth lens group G4. It is used for seven surfaces on the image side of the meniscus lens.

  The numerical data of the lens in each example is shown below.

In the numerical data of the lens in each embodiment, R is the radius of curvature of each lens surface, D is the thickness or spacing of each lens, Nd is the refractive index at the d-line of each lens, and νd is the Abbe at the d-line of each lens. Number, K is a conical coefficient, A4, A6, A8, and A10 are aspheric coefficients, and E ± n is × 10 ± ⁿ .

  Each aspheric shape is expressed by the following expression using each aspheric coefficient in each embodiment.

Z = (Y ² / r) / [1+ {1− (1 + K) · (Y / r) ² } ^1/2 ]
+ A4 × Y ⁴ + A6 × Y ⁶ + A8 × Y ⁸ + A10 × Y ¹⁰
However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.

Numerical example 1
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -11.981 0.70 1.58313 59.38
2 (Aspherical surface) 37.532 0.70 1.63494 23.22
3 (Aspherical) -210.729 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 4.871 1.50 1.83481 42.71
6 (Aspherical surface) -86.685 0.15
7 13.016 1.08 1.88300 40.76
8 457.725 0.51 1.80518 25.42
9 3.309 Variable
10 50.796 0.80 1.52542 55.78
11 (Aspherical) 23.127 Variable
12 30.869 2.60 1.58313 59.38
13 (Aspherical) -9.130 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 0.696, A4 = 8.15954E-04, A6 = -9.02964E-06, A8 = 7.06618E-08, A10 = 1.64985E-10
Second side
K = -7.816, A4 = 5.93790E-04, A6 = -1.17684E-05
Third side
K = -418.955, A4 = 5.24806E-04, A6 = -3.91612E-06, A8 = -1.24273E-07, A10 = 2.82606E-09
5th page
K = 0.139, A4 = -6.03643E-04, A6 = -5.31230E-05, A8 = 2.70195E-06
6th page
K = 0.000, A4 = 6.99714E-04, A6 = -7.25503E-05, A8 = 8.68547E-06, A10 = -1.54245E-07
11th page
K = 0.000, A4 = -1.32093E-05, A6 = -4.00985E-06, A8 = 1.56930E-07, A10 = -5.79143E-09
13th page
K = -0.432, A4 = 3.83764E-04, A6 = -7.83432E-06, A8 = 1.38963E-07, A10 = -4.62646E-10

Various data Zoom ratio 2.87
Wide-angle Wide-angle change point Intermediate Telephoto change point Telephoto focal length 7.71 10.35 13.4 18.19 22.1
F number 2.88 3.4 3.98 4.79 5.49
Angle of view 63.51 47.92 37.44 28.04 23.39
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 32.46 30.10 29.46 29.49 30.79
BF 5.41 4.78 4.31 4.14 3.92

d3 15.26 10.54 7.33 3.74 2.18
d9 1 5.1 7.34 10.76 12.11
d11 2.76 1.65 2.46 2.82 4.55
d13 3.76 3.13 2.66 2.49 2.27

Zoom lens group data Group Start surface Focal length
1 1 -22.66
2 5 12.16
3 10 -81.62
4 12 12.38

Numerical example 2
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -14.217 0.70 1.58313 59.38
2 (Aspherical surface) 24.136 0.65 1.63494 23.22
3 (Aspherical surface) 72.792 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical surface) 4.961 1.54 1.82080 42.71
6 (Aspherical surface) -89.208 0.15
7 11.451 1.00 1.88300 40.76
8 142.631 0.51 1.80518 25.42
9 3.372 Variable
10 29.312 0.80 1.52542 55.78
11 (Aspherical) 21.393 Variable
12 49.315 2.47 1.52542 55.78
13 (Aspherical) -8.540 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 2.777, A4 = 4.38487E-04, A6 = 1.16381E-05, A8 = -3.29372E-07, A10 = 4.18427E-09
Second side
K = -3.418, A4 = 5.12543E-04, A6 = -3.82583E-06
Third side
K = 26.883, A4 = 1.65598E-04, A6 = 1.41400E-05, A8 = -3.80117E-07, A10 = 3.81175E-09
5th page
K = 0.348, A4 = -8.05884E-04, A6 = -5.80311E-05, A8 = 2.18950E-06
6th page
K = 0.000, A4 = 6.47271E-04, A6 = -5.81071E-05, A8 = 7.29418E-06, A10 = -3.29262E-08
11th page
K = 0.000, A4 = 1.33935E-04, A6 = -1.96248E-05, A8 = 4.60497E-07, A10 = -6.31473E-09
13th page
K = -0.391, A4 = 2.59050E-04, A6 = 2.68519E-06, A8 = 6.96644E-08, A10 = -4.04915E-10

Various data Zoom ratio 2.88
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 7.78 10.35 13.4 18 22.42
F number 2.88 3.44 4 4.84 5.51
Angle of view 63.34 48.08 37.52 28.21 22.88
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.66 30.64 29.80 30.32 31.57
BF 5.48 4.65 4.20 3.74 4.04

d3 14.57 10.9 7.6 4.66 2.38
d9 1.58 4.35 7.94 10.8 14.07
d11 2.21 2.93 2.24 3.3 3.27
d13 3.83 3 2.55 2.09 2.39

Zoom lens group data Group Start surface Focal length
1 1 -20.90
2 5 11.88
3 10 -156.15
4 12 14.06

Numerical Example 3
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -14.249 0.70 1.58313 59.38
2 (Aspherical) 23.234 0.57 1.63494 23.22
3 (Aspherical) 86.974 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 5.042 1.49 1.83481 42.71
6 (Aspherical surface) -86.330 0.15
7 12.427 1.02 1.88300 40.76
8 509.464 0.55 1.80518 25.42
9 3.426 Variable
10 25.791 0.80 1.52542 55.78
11 (Aspherical) 20.006 Variable
12 35.484 2.60 1.52542 55.78
13 (Aspherical) -9.171 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 2.687, A4 = 5.38597E-04, A6 = 4.61021E-06, A8 = -1.84142E-07, A10 = 2.94944E-09
Second side
K = -2.810, A4 = 3.98204E-04, A6 = -4.78082E-06
Third side
K = 19.023, A4 = 2.58400E-04, A6 = 6.91398E-06, A8 = -2.61693E-07, A10 = 3.30720E-09
5th page
K = -0.334, A4 = -8.96571E-05, A6 = -3.54061E-05, A8 = 2.97005E-06
6th page
K = 0.000, A4 = 6.29371E-04, A6 = -6.76395E-05, A8 = 7.12232E-06, A10 = -1.56331E-07
11th page
K = 0.000, A4 = 2.01335E-05, A6 = -1.19486E-05, A8 = 2.65168E-07, A10 = -3.91123E-09
13th page
K = -1.321, A4 = 2.34507E-04, A6 = -5.97599E-06, A8 = 2.24954E-07, A10 = -1.97170E-09

Various data Zoom ratio 2.82
Wide-angle Wide-angle change point Intermediate Telephoto change point Telephoto focal length 8.02 10.35 13.4 18.2 22.64
F number 2.88 3.36 3.92 4.76 5.45
Angle of view 61.72 48.07 37.54 27.93 22.67
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.67 30.58 29.80 30.29 31.62
BF 5.44 4.79 4.30 3.89 4.01

d3 14.45 10.94 7.63 4.43 2.29
d9 1.49 3.95 7.76 10.93 13.79
d11 2.41 3.02 2.23 3.17 3.66
d13 3.79 3.14 2.65 2.24 2.36

Zoom lens group data Group Start surface Focal length
1 1 -21.65
2 5 12.13
3 10 -178.21
4 12 14.15

Numerical Example 4
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -18.911 0.80 1.58313 59.38
2 12.725 0.80 1.63494 23.22
3 (Aspherical) 30.290 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 6.081 1.60 1.74320 49.34
6 (Aspherical surface) -22.773 0.15
7 10.604 1.69 1.83481 42.71
8 134.114 0.52 1.80518 25.42
9 3.704 Variable
10 56.233 0.80 1.52542 55.78
11 (Aspherical) 17.069 Variable
12 134.146 2.18 1.80610 40.92
13 (Aspherical) -10.349 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 1.051, A4 = 5.07602E-06, A6 = 1.30112E-05, A8 = -2.87458E-07, A10 = 2.32505E-09
Third side
K = 26.006, A4 = -2.35130E-04, A6 = 1.12544E-05, A8 = -1.09983E-07, A10 = -4.61435E-09
5th page
K = -1.634, A4 = -9.16990E-05, A6 = -1.18179E-04, A8 = 1.12848E-05, A10 = -2.01021E-06
6th page
K = -37.172, A4 = -7.71139E-04, A6 = -1.00279E-04, A8 = 5.88476E-06, A10 = -1.42926E-06
11th page
K = 0.000, A4 = 2.19655E-04, A6 = 2.87695E-06, A8 = -1.81203E-06, A10 = 4.76216E-08
13th page
K = -2.283, A4 = -1.17618E-04, A6 = -2.42901E-08, A8 = 6.63928E-08, A10 = 1.33000E-09

Various data Zoom ratio 2.88
Wide-angle Wide-angle change point Intermediate Telephoto change point Telephoto focal length 8.16 10.44 13.55 18.12 23.5
F number 2.88 3.36 3.91 4.77 5.67
Angle of view 60.96 47.28 36.44 27.49 21.38
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.65 30.66 29.65 30.22 31.53
BF 5.67 4.94 4.51 3.90 3.71

d3 13.45 10.38 7.12 4.57 2.4
d9 1.51 4.03 6.73 9.17 11.92
d11 2.5 2.78 2.76 4.05 4.98
d13 4.02 3.28 2.85 2.25 2.06

Zoom lens group data Group Start surface Focal length
1 1 -20.72
2 5 11.30
3 10 -46.98
4 12 12.00

Numerical Example 5
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -22.653 0.70 1.58313 59.38
2 16.559 0.53 1.63494 23.22
3 (Aspherical) 25.127 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical surface) 4.860 1.49 1.83481 42.71
6 (Aspherical surface) -106.734 0.15
7 10.872 1.03 1.83481 42.71
8 48.837 0.54 1.80518 25.42
9 3.226 Variable
10 35.000 0.80 1.52542 55.78
11 (Aspherical) 21.080 Variable
12 31.125 2.43 1.52542 55.78
13 (Aspherical) -9.817 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 4.541, A4 = -2.29064E-04, A6 = 2.09731E-05, A8 = -3.82878E-07, A10 = 2.81320E-09
Third side
K = 15.256, A4 = -4.82788E-04, A6 = 1.65349E-05, A8 = -1.40821E-07, A10 = -3.15256E-09
5th page
K = -0.919, A4 = 3.68452E-04, A6 = 4.06370E-06, A8 = 7.47374E-07
6th page
K = 0.000, A4 = 4.16616E-04, A6 = -9.39191E-06, A8 = 8.31094E-07
11th page
K = 0.000, A4 = -1.88499E-05, A6 = -1.78170E-05, A8 = 2.94314E-07, A10 = -5.69112E-09
13th page
K = -1.098, A4 = 8.78574E-05, A6 = 8.97907E-06, A8 = -2.39271E-07, A10 = 6.89604E-09

Various data Zoom ratio 2.88
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 8.15 10.43 13.53 18.1 23.48
F number 2.86 3.35 3.88 4.65 5.45
Angle of view 61.03 47.85 37.35 28.09 21.8
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.65 30.93 29.71 30.02 31.65
BF 5.44 4.56 4.15 3.86 4.17

d3 14.57 11.58 8.06 5.01 2.5
d9 1.5 3.93 7.57 10.38 13.57
d11 2.48 3.2 2.27 3.11 3.75
d13 3.79 2.91 2.5 2.21 2.51

Zoom lens group data Group Start surface Focal length
1 1 -20.70
2 5 11.64
3 10 -102.92
4 12 14.50

Numerical Example 6
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -33.739 0.80 1.58313 59.38
2 13.645 0.67 1.63494 23.22
3 (Aspherical) 19.343 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 5.010 1.44 1.83481 42.71
6 (Aspherical surface) -69.498 0.15
7 11.772 1.10 1.83481 42.71
8 -614.613 0.50 1.80518 25.42
9 3.408 Variable
10 212.094 0.80 1.52542 55.78
11 (Aspherical) 24.454 Variable
12 103.939 2.11 1.74320 49.34
13 (Aspherical) -10.380 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = 8.816, A4 = -4.13122E-04, A6 = 2.62067E-05, A8 = -5.70488E-07, A10 = 4.91698E-09
Third side
K = 9.676, A4 = -7.27584E-04, A6 = 2.58033E-05, A8 = -5.21907E-07, A10 = -1.06649E-09
5th page
K = -1.245, A4 = 7.19784E-04, A6 = -1.53107E-05, A8 = 3.19896E-06
6th page
K = 0.000, A4 = 5.31100E-04, A6 = -2.86233E-05, A8 = 3.81056E-06
11th page
K = 0.000, A4 = 1.07531E-04, A6 = -9.60733E-07, A8 = -7.21707E-07, A10 = 1.57456E-08
13th page
K = -0.560, A4 = 2.26496E-04, A6 = -1.07789E-05, A8 = 4.12967E-07, A10 = -3.58833E-09

Various data Zoom ratio 2.88
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 8.08 10.34 13.41 17.93 23.26
F number 2.87 3.32 3.9 4.7 5.61
Angle of view 61.37 47.82 36.98 27.94 21.79
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.35 29.99 29.27 29.46 30.75
BF 6.13 5.39 4.77 4.22 3.85

d3 14 10.62 7.52 4.61 2.5
d9 1.15 4.22 6.96 10.08 12.89
d11 2.51 2.2 2.46 2.98 3.95
d13 4.48 3.74 3.12 2.57 2.2

Zoom lens group data Group Start surface Focal length
1 1 -21.39
2 5 11.52
3 10 -52.69
4 12 12.80

Numerical Example 7
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -44.139 0.70 1.58313 59.38
2 12.363 0.67 1.63494 23.22
3 (Aspherical) 16.544 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 4.836 1.66 1.80139 45.46
6 (Aspherical surface) -49.496 0.15
7 11.072 1.40 1.80810 22.76
8 3.337 Variable
9 100.000 0.80 1.52542 55.78
10 (Aspherical) 25.815 Variable
11 25.727 2.46 1.52542 55.78
12 (Aspherical) -10.468 Variable
13 ∞ 0.50 1.54771 62.84
14 ∞ 0.50
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = -38.771, A4 = -6.70403E-04, A6 = 3.53973E-05, A8 = -7.64753E-07, A10 = 6.56335E-09
Third side
K = 6.806, A4 = -8.94941E-04, A6 = 3.38549E-05, A8 = -6.96377E-07, A10 = -1.43567E-10
5th page
K = -1.226, A4 = 7.06424E-04, A6 = 1.12713E-06, A8 = 6.74850E-07
6th page
K = -259.534, A4 = 2.66611E-04
10th page
K = 0.000, A4 = -1.42025E-04, A6 = -1.27034E-06, A8 = -6.79574E-07, A10 = 1.28770E-08
12th page
K = -9.186, A4 = -5.90762E-04, A6 = 1.89978E-05, A8 = -3.29764E-07, A10 = 6.07274E-09

Various data Zoom ratio 2.88
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 8.16 10.44 13.55 18.11 23.5
F number 2.89 3.36 3.91 4.71 5.5
Angle of view 60.93 47.88 37.16 27.94 21.53
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 32.15 31.17 30.18 30.58 32.10
BF 6.07 5.26 4.71 4.22 4.69

d3 14.8 11.55 8.19 5.25 2.6
d8 1 3.68 6.75 9.58 12.29
d10 2.46 2.86 2.71 3.7 4.7
d12 4.42 3.6 3.06 2.57 3.04

Zoom lens group data Group Start surface Focal length
1 1 -20.95
2 5 11.71
3 9 -66.47
4 11 14.50

Numerical Example 8
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -14.890 0.70 1.58313 59.38
2 15.930 0.68 1.63494 23.22
3 (Aspherical) 49.617 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical surface) 4.953 1.68 1.69350 53.21
6 (Aspherical surface) -30.326 0.20
7 9.435 1.52 1.80810 22.76
8 3.555 Variable
9 80.000 0.80 1.52542 55.78
10 (Aspherical) 26.236 Variable
11 -82.545 1.90 1.74320 49.34
12 (Aspherical) -10.496 Variable
13 ∞ 0.50 1.54771 62.84
14 ∞ 0.50
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = -16.025, A4 = -3.11310E-04, A6 = 1.28912E-05, A8 = -2.32621E-07, A10 = 1.94746E-09
Third side
K = 70.098, A4 = 2.81845E-05, A6 = 1.91821E-07, A8 = 5.60745E-08, A10 = -2.48830E-09
5th page
K = -1.211, A4 = 4.77122E-04, A6 = 2.36137E-06, A8 = 3.39207E-07, A10 = 2.60202E-09
6th page
K = 0.000, A4 = 4.20224E-04, A6 = -3.82318E-06
10th page
K = 0.000, A4 = 3.32937E-05, A6 = 4.46490E-06, A8 = -2.08795E-06, A10 = 7.95117E-08
12th page
K = -9.714, A4 = -7.62805E-04, A6 = 1.43896E-05, A8 = -6.63909E-08, A10 = -7.05542E-10

Various data Zoom ratio 2.88
Wide-angle Wide-angle change point Intermediate Telephoto change point Telephoto focal length 8.16 10.44 13.55 18.12 23.5
F number 2.89 3.3 3.84 4.63 5.49
Angle of View 62.74 48.44 37.19 27.94 21.69
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 32.45 30.57 29.80 30.53 32.38
BF 6.62 6.05 5.65 5.22 5.23

d3 14.75 10.89 7.57 4.75 2.53
d8 1.1 3.82 5.84 7.63 9.42
d10 2.5 2.33 3.25 5.45 7.72
d12 4.97 4.4 4 3.57 3.58

Zoom lens group data Group Start surface Focal length
1 1 -20.38
2 5 11.59
3 9 -74.68
4 11 16.00

Numerical Example 9
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -14.706 0.70 1.58313 59.38
2 18.885 0.78 1.63494 23.22
3 (Aspherical) 49.972 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical) 5.032 1.71 1.74320 49.34
6 (Aspherical surface) -30.235 0.30
7 10.531 1.49 1.80810 22.76
8 3.487 Variable
9 80.000 0.80 1.52542 55.78
10 (Aspherical) 26.257 Variable
11 (Aspherical) 61.805 2.40 1.52542 55.78
12 (Aspherical) -9.600 Variable
13 ∞ 0.50 1.54771 62.84
14 ∞ 0.50
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = -15.776, A4 = -4.22513E-04, A6 = 1.52534E-05, A8 = -2.58294E-07, A10 = 2.15094E-09
Third side
K = 62.986, A4 = -5.46325E-05, A6 = 5.22355E-07, A8 = 7.47251E-08, A10 = -2.59679E-09
5th page
K = -1.375, A4 = 5.92760E-04, A6 = 3.29704E-06, A8 = -2.37832E-07
6th page
K = 58.183, A4 = 6.74242E-04, A6 = 6.09294E-06
10th page
K = 0.000, A4 = -2.61727E-05, A6 = 5.69324E-06, A8 = -1.96963E-06, A10 = 6.99317E-08
11th page
K = 70.208
12th page
K = -8.029, A4 = -7.13654E-04, A6 = 1.19084E-05, A8 = 1.96023E-08, A10 = -1.05869E-09

Various data Zoom ratio 2.88
Wide-angle Wide-angle change point Intermediate Telephoto change point Telephoto focal length 8.12 10.4 13.48 18.03 23.39
F number 2.89 3.3 3.84 4.6 5.45
Angle of view 63.95 49.24 37.8 28.36 22.02
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 32.45 30.57 29.80 30.43 32.40
BF 5.93 5.35 4.97 4.80 5.05

d3 14.93 11.15 7.91 4.98 2.73
d8 1.1 3.88 5.84 7.43 9.23
d10 2.5 2.2 3.1 5.23 7.41
d12 4.28 3.7 3.31 3.14 3.4

Zoom lens group data Group Start surface Focal length
1 1 -19.69
2 5 11.34
3 9 -74.77
4 11 16.00

Numerical Example 10
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -14.992 0.70 1.58313 59.38
2 (Aspherical) 13.949 0.70 1.63387 23.38
3 (Aspherical) 37.831 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical surface) 5.607 1.58 1.74320 49.34
6 (Aspherical surface) -32.147 0.15
7 8.542 1.77 1.92286 18.90
8 3.770 Variable
9 80.000 0.80 1.52542 55.78
10 (Aspherical) 22.579 Variable
11 195.714 2.22 1.74320 49.34
12 (Aspherical) -11.538 Variable
13 ∞ 0.50 1.54771 62.84
14 ∞ 0.50
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = -3.208, A4 = 1.45834E-05, A6 = 9.31907E-06, A8 = -2.35085E-07, A10 = 2.17381E-09
Second side
K = -3.058, A4 = -9.88721E-05, A6 = 2.22517E-05, A8 = -4.94745E-07
Third side
K = 0.000, A4 = -2.95854E-05, A6 = 1.64938E-05, A8 = -4.19469E-07, A10 = 4.62753E-09
5th page
K = -1.749, A4 = 6.63921E-04, A6 = -1.17196E-05, A8 = -1.16625E-06, A10 = 3.08705E-08
6th page
K = 0.000, A4 = 3.37846E-04, A6 = -2.69871E-05
10th page
K = 0.000, A4 = 6.52998E-05, A6 = 3.66885E-07, A8 = -4.92201E-07, A10 = 1.40308E-08
12th page
K = -5.146, A4 = -2.75156E-04, A6 = 1.08356E-06, A8 = 4.53615E-08, A10 = -5.01467E-10

Various data Zoom ratio 2.89
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 8.14 10.42 13.37 18.09 23.52
F number 2.88 3.3 3.83 4.63 5.53
Angle of View 64.45 49.15 37.97 28.18 21.93
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 31.19 29.71 29.25 30.07 32.09
BF 6.01 5.44 5.03 4.82 4.76

d3 13.36 9.92 7.08 4.25 2.28
d8 1.58 4.13 6.12 8.16 10.54
d10 2.33 2.29 3.1 4.91 6.6
d12 4.38 3.81 3.41 3.21 3.15

Zoom lens group data Group Start surface Focal length
1 1 -19.05
2 5 10.99
3 9 -60.16
4 11 14.73

Numerical Example 11
Unit mm

Surface data surface number r d nd νd
1 (Aspherical surface) -15.671 0.70 1.58313 59.38
2 (Aspherical) 14.047 0.70 1.63387 23.38
3 (Aspherical) 35.585 Variable
4 (Aperture) ∞ 0.00
5 (Aspherical surface) 5.496 1.57 1.74320 49.34
6 (Aspherical surface) -35.657 0.15
7 8.705 1.82 1.92286 18.90
8 3.746 Variable
9 80.000 0.80 1.52542 55.78
10 (Aspherical) 29.136 Variable
11 -419.759 2.20 1.74320 49.34
12 (Aspherical) -10.902 Variable
13 ∞ 0.50 1.54771 62.84
14 ∞ 0.50
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.50
Image plane ∞

Aspheric data first surface
K = -3.122, A4 = -3.61952E-05, A6 = 1.00973E-05, A8 = -2.32003E-07, A10 = 2.09996E-09
Second side
K = 0.970, A4 = -2.46910E-04, A6 = 1.48213E-05, A8 = -2.65313E-07
Third side
K = 0.000, A4 = -8.54922E-05, A6 = 1.65424E-05, A8 = -3.97467E-07, A10 = 4.80196E-09
5th page
K = -1.838, A4 = 8.72041E-04, A6 = 1.55077E-05, A8 = -5.16964E-06, A10 = 5.97515E-07
6th page
K = 0.000, A4 = 4.66902E-04, A6 = 5.33655E-06, A8 = -4.29970E-06, A10 = 6.58448E-07
10th page
K = 0.000, A4 = 1.83567E-04, A6 = -1.58925E-05, A8 = 5.62901E-07, A10 = -1.12511E-08
12th page
K = -6.584, A4 = -5.37999E-04, A6 = 1.01657E-05, A8 = -1.17559E-07, A10 = 5.95227E-10

Various data Zoom ratio 2.88
Wide-angle Wide-angle side change point Intermediate Telephoto-side change point Telephoto focal length 8.16 10.5 13.39 18.08 23.51
F number 2.88 3.31 3.78 4.63 5.56
Angle of view 64.38 48.82 37.99 28.28 22.06
Image height 4.55 4.55 4.55 4.55 4.55
Total lens length 30.97 29.43 28.51 29.82 31.98
BF 5.81 5.26 5.02 4.67 4.51

d3 13.27 9.74 6.63 4.15 2.27
d8 1.59 4.53 7.88 8.34 10.06
d10 2.36 1.96 1.04 4.72 7.2
d12 4.15 3.61 3.37 3.01 2.85

Zoom lens group data Group Start surface Focal length
1 1 -19.27
2 5 11.06
3 9 -87.69
4 11 15.03

  FIGS. 12 to 33 show aberration diagrams of Examples 1 to 11 when focusing on an object point at infinity, respectively. In these aberration diagrams, (a) is the wide angle end, (b) is the change point on the wide angle side, (c) is the intermediate state, (d) is the change point on the telephoto side, (e) is the spherical aberration at the telephoto end, astigmatism Aberration, distortion, and lateral chromatic aberration are shown. In each figure, “FIY” indicates a half angle of view.

  Next, the values of conditional expressions (1) to (10) in the above-described embodiments will be shown. For Examples 1 to 6, conditional expression (4) is excluded. Further, fs represents a focal length fs = √ (fw · ft) in an intermediate state of each embodiment, and conditional expressions (6) to (10) represent values at the focal length fs.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
(1) -0.946 -0.865 -0.888 -0.869 -0.915 -0.851
(2) 0.182 0.173 0.158 0.196 0.151 0.181
(3) 36.165 36.165 36.165 36.165 36.165 36.165
(5) 2.467 2.529 2.469 2.426 2.593 2.488
fs 1.026 1.015 0.994 0.978 0.978 0.978
(6) -0.389 -0.239 -0.233 -0.246 -0.238 -0.257
(7) -2.250 -1.048 -1.028 -1.065 -1.000 -1.405
(8) 0.762 0.732 0.691 0.654 0.609 0.676
(9) -0.823 -1.441 -1.165 -0.636 -1.000 -2.466
(10) 0.357 0.129 0.257 0.680 -0.013 0.675

Conditional Example Example 7 Example 8 Example 9 Example 10 Example 11
(1) -0.864 -0.797 -0.852 -0.768 -0.805
(2) 0.167 0.169 0.158 0.172 0.172
(3) 36.165 36.165 36.165 35.998 35.998
(4A) 1.801 1.694 1.743 1.743 1.743
(4B) 45.456 53.210 49.340 49.340 49.340
(4C) 22.760 22.760 22.760 18.900 18.900
(5) 2.557 2.415 2.485 2.449 2.438
fs 0.978 0.978 0.978 0.966 0.967
(6) -0.241 -0.325 -0.327 -0.238 -0.302
(7) -1.025 -1.028 -1.019 -0.681 -0.711
(8) 0.619 0.594 0.562 0.567 0.534
(9) -0.560 -0.053 -0.084 -0.064 -0.374
(10) 0.014 0.430 -0.088 0.280 0.661

  In each embodiment, the following configuration may be adopted.

  In order to cut off unnecessary light such as ghost and flare, a flare stop other than the brightness stop S may be arranged. The object side of the first lens group G1, between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, and fourth. It may be arranged at any location between the lens group G4 and the image plane I. Moreover, you may comprise so that a flare ray may be cut with a frame member, and you may comprise another member. Also, it may be printed directly on the surface of the lens, painted, or adhered with a seal or the like. Further, the shape may be any shape such as a circle, an ellipse, a rectangle, a polygon, or a range surrounded by a function curve. Further, not only the harmful light flux but also the light flux such as coma flare around the screen may be cut.

  Each lens may be provided with an antireflection coating to reduce ghosts and flares. A multi-coat is desirable because it can effectively reduce ghost and flare. Moreover, you may give an infrared cut coat to a lens surface, a cover glass, etc.

  Further, it is desirable to perform focusing for adjusting the focus with the fourth lens group G4. When focusing is performed with the fourth lens group G4, the load on the drive system such as a motor is small because the lens weight is light. Furthermore, the total length does not change during focusing, and the drive motor can be arranged inside the lens frame, which is advantageous for making the lens frame compact. As described above, the fourth lens group G4 focusing is desirable, but the first lens group G1, the second lens group G2, and the third lens group G3 may perform focusing. Further, focusing may be performed by moving a plurality of lens groups. Further, focusing may be performed by extending the entire lens system, or a part of the lenses in the group may be extended or focused by focusing.

  Further, the shading of the brightness at the periphery of the image may be reduced by shifting the micro lens of the CCD. For example, the design of the CCD microlens may be changed in accordance with the incident angle of the light beam at each image height. Further, the amount of decrease in the peripheral portion of the image may be corrected by image processing.

  Alternatively, the distortion may be intentionally generated by the optical system, and the distortion may be corrected by electrically performing image processing after shooting. Each of the zoom lenses according to the embodiments may be used to electrically correct distortion.

  In the zoom lens of this embodiment, a barrel-shaped distortion is left on the rectangular photoelectric conversion surface in the vicinity of the wide-angle end. On the other hand, the occurrence of distortion changes near the intermediate focal length state and at the telephoto end. When the distortion aberration is electrically corrected, the effective imaging region is changed to have a barrel shape at the wide-angle end and a rectangular shape at the intermediate focal length state or the telephoto end. Then, the effective imaging area set in advance is image-converted by image processing and converted into rectangular image information with reduced distortion. The maximum image height IHw at the wide angle end is converted to be smaller than the maximum image height IHs at the intermediate focal length state and the maximum image height IHt at the telephoto end.

  For example, at the wide-angle end, the length in the short side direction of the photoelectric conversion surface is the same as the length in the short side direction of the effective image pickup region, and the effective image pickup region is left so that distortion after image processing remains about −3%. May be determined. Of course, an image obtained by converting a smaller barrel-shaped area into a rectangular shape as an effective imaging area may be recorded and reproduced.

For example, as shown in FIG. 34, the magnification on the circumference (image height) of the radius R inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface is fixed, and this circumference is The standard for correction. Then, correction is performed by moving each point on the circumference (image height) of any other radius r (ω) in a substantially radial direction and concentrically so as to have the radius r ′ (ω). To do. For example, in FIG. 34, a point P ₁ on the circumference of an arbitrary radius r ₁ (ω) located inside the circle of radius R is a radius r ₁ ′ (ω) circle to be corrected toward the center of the circle. Move to point P ₂ on the circumference. A point Q ₁ on the circumference of an arbitrary radius r ₂ (ω) located outside the circle of radius R is on the radius r ₂ ′ (ω) circumference to be corrected in a direction away from the center of the circle. To point Q ₂ . Here, r ′ (ω) can be expressed as follows.

r ′ (ω) = αf tan ω (0 ≦ α ≦ 1)
Here, ω is the half-angle of the subject, and f is the focal length of the imaging optical system (in the present invention, the zoom lens).

Here, if the ideal image height corresponding to the circle (image height) of the radius r is Y,
α = R / Y = R / ftanω
It becomes.

  The optical system is ideally rotationally symmetric with respect to the optical axis, that is, distortion is also generated rotationally symmetric with respect to the optical axis. Therefore, as described above, when the optically generated distortion aberration is electrically corrected, the radius inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface on the reproduced image. The magnification on the circumference of the circle of R (image height) is fixed, and the other points on the circumference of the circle (image height) of radius r (ω) are moved in a substantially radial direction to obtain a radius r ′ ( If correction can be performed by moving the concentric circles so that ω), it is considered advantageous in terms of data amount and calculation amount.

However, the optical image is no longer a continuous amount (due to sampling) when captured by the electronic image sensor. Therefore, strictly speaking, the circle with the radius R drawn on the optical image is not an accurate circle unless the pixels on the electronic image sensor are arranged radially. That is, in the shape correction of the image data represented for each discrete coordinate point, there is no circle that can fix the magnification. Therefore, it is preferable to use a method of determining the coordinates (X ′ _i , Y ′ _j ) of the movement destination for each pixel (X _i , Y _j ). When two or more points (X _i , Y _j ) have moved to the coordinates (X ′ _i , Y ′ _j ), the average value of the values of each pixel is taken. If there is no moving point, interpolation may be performed using the values of the coordinates (X ′ _i , Y ′ _j ) of some surrounding pixels.

  Such a method is particularly distorted with respect to the optical axis due to a manufacturing error of an optical system or an electronic imaging element in an electronic imaging device included in a zoom lens, and the circle with the radius R drawn on the optical image is It is effective for correction when it becomes asymmetric. Further, it is effective for correction when a geometric distortion or the like occurs when a signal is reproduced as an image in an image sensor or various output devices.

  In the electronic imaging apparatus of the present invention, in order to calculate the correction amount r ′ (ω) −r (ω), r (ω), that is, the relationship between the half field angle and the image height, or the real image height r and the ideal image height. The relationship between r ′ / α may be recorded on a recording medium built in the electronic imaging apparatus.

  Note that the radius R preferably satisfies the following conditional expression so that the image after distortion correction does not have an extremely short amount of light at both ends in the short side direction.

0 ≦ R ≦ 0.6L _s
Note that L _s is the length of the short side of the effective imaging surface.

  Preferably, the radius R satisfies the following conditional expression.

0.3 ≦ R ≦ 0.6L _s
Furthermore, it is most advantageous that the radius R coincides with the radius of the inscribed circle in the short side direction of the substantially effective imaging surface. In the case of correction in which the magnification is fixed in the vicinity of the radius R = 0, that is, in the vicinity of the axis, there is a slight disadvantage in terms of the actual number of pixels, but the effect of reducing the size is ensured even if the angle is widened. it can.

The focal length section that needs to be corrected is divided into several focal zones. Then, in the vicinity of the telephoto end in the divided focal zone, approximately r ′ (ω) = αf tan ω
You may correct | amend with the same correction amount as the case where the correction result which satisfies is obtained. However, in that case, some barrel distortion remains at the wide-angle end in the divided focal zone. Further, if the number of divided zones is increased, it becomes unnecessary to store extraneous data necessary for correction on the recording medium, which is not preferable. Therefore, one or several coefficients related to each focal length in the divided focal zone are calculated in advance. This coefficient may be determined on the basis of simulation or actual measurement. Then, in the vicinity of the telescope in the divided zone, approximately r ′ (ω) = αf tan ω
It is also possible to calculate a correction amount when a correction result satisfying the above is obtained, and uniformly multiply the correction amount for each focal distance to obtain a final correction amount.

By the way, if there is no distortion in the image obtained by imaging an object at infinity,
f = y / tan ω
Is established. Where y is the height of the image point from the optical axis (image height), f is the focal length of the imaging system (in the present invention, the zoom lens), and ω is the image point connected from the center on the imaging surface to the y position. It is an angle (subject half field angle) with respect to the optical axis in the corresponding object direction.

If the imaging system has barrel distortion,
f> y / tan ω
It becomes. That is, if the focal length f of the imaging system and the image height y are constant, the value of ω increases.

35 to 37 are conceptual diagrams of the configuration of the digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 41. FIG. FIG. 35 is a front perspective view showing the external appearance of the digital camera 40, FIG. 36 is a rear front view thereof, and FIG. 37 is a schematic cross-sectional view showing the configuration of the digital camera 40. However, in FIGS. 35 and 37, the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 located on the photographing optical path 42, a finder optical system 43 located on the finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length. When the photographic optical system 41 is retracted, the photographic optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 when the photographic optical system 41 is retracted. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 is brought into the non-collapsed state of FIG. Photographing is performed through the optical system 41, for example, the zoom lens of the first embodiment. An object image formed by the photographic optical system 41 is formed on the imaging surface (photoelectric conversion surface) of the CCD 49 via a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. The processing means 51 is connected to a recording means 52 and can record a captured electronic image. The recording means 52 may be provided separately from the processing means 51 or may be a floppy (registered). (Trademark) The recording and writing may be performed electronically using a disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a plurality of lens groups (three groups in the figure) and an erecting prism system 55 including erecting prisms 55a, 55b, and 55c, and is linked to the zoom lens of the photographing optical system 41. The object image formed by the finder objective optical system 53 is formed on a field frame 57 of an erecting prism system 55 that is an image erecting member. Behind the erecting prism system 55, an eyepiece optical system 59 for guiding the erect image to the observer eyeball E is disposed. A cover member 50 is disposed on the exit side of the eyepiece optical system 59.

  FIG. 38 is a block diagram showing the internal circuitry of the main part of the digital camera 40. In the following description, the processing unit 51 includes, for example, the CDS / ADC unit 24, the primary storage memory 17, the image processing unit 18, and the storage unit 52 includes the storage medium unit 19, for example.

  As shown in FIG. 38, the digital camera 40 is connected via the buses 14 and 15 to the operation unit 12, the control unit 13 connected to the operation unit 12, and the control signal output port of the control unit 13. An imaging drive circuit 16, a primary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21 are provided.

  The primary storage memory 17, the image processing unit 18, the storage medium unit 19, the display unit 20, and the setting information storage memory unit 21 are configured so that data can be input or output with each other via the bus 22. The imaging drive circuit 16 is connected with a CCD 49 and a CDS / ADC unit 24.

The operation unit 12 includes various input buttons and switches, and is a circuit that notifies the control unit of event information input from the outside (camera user) via these input buttons and switches.
The control unit 13 is a central processing unit composed of, for example, a CPU, and has a built-in program memory (not shown). The control unit 13 is input by a camera user via the operation unit 12 according to a program stored in the program memory. This circuit controls the entire digital camera 40 in response to the instruction command.

  The CCD 49 receives an object image formed via the photographing optical system 41 according to the present invention. The CCD 49 is an image pickup element that is driven and controlled by the photographing drive circuit 16 and converts the light amount of each pixel of the object image into an electrical signal and outputs it to the CDS / ADC unit 24.

  The CDS / ADC unit 24 amplifies the electric signal input from the CCD 49 and performs analog / digital conversion, and temporarily generates the raw video data (Bayer data, hereinafter referred to as RAW data) that has just been subjected to the amplification and digital conversion. It is a circuit that outputs to the memory 17.

  The primary storage memory 17 is a buffer made of, for example, SDRAM, and is a memory device that temporarily stores the RAW data output from the CDS / ADC unit 24. The image processing unit 18 reads out the RAW data stored in the primary storage memory 17 or the RAW data stored in the storage medium unit 19, and performs various corrections including distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs image processing electrically.

  The storage medium unit 19 detachably mounts a card-type or stick-type recording medium made of, for example, a flash memory, and the RAW data transferred from the primary storage memory 17 to the card-type or stick-type flash memory It is a control circuit of an apparatus that records and holds image data processed by the image processing unit 18.

  The display unit 20 includes a liquid crystal display monitor 47 and is a circuit that displays an image, an operation menu, and the like on the liquid crystal display monitor 47. The setting information storage memory unit 21 stores a ROM unit in which various image quality parameters are stored in advance, and an image quality parameter selected by an input operation of the operation unit 12 among the image quality parameters read from the ROM unit. RAM section is provided. The setting information storage memory unit 21 is a circuit for controlling input / output to / from these memories.

  In the digital camera 40 configured in this manner, the imaging optical system 41 has a sufficiently wide angle range according to the present invention, and a compact configuration, while the imaging performance is extremely stable at a high zoom ratio and in a full zoom ratio range. Therefore, high performance, downsizing, and wide angle can be realized. In addition, fast focusing operation on the wide-angle side and the telephoto side is possible.

  The present invention may be applied not only to a so-called compact digital camera that captures a general subject as described above, but also to a surveillance camera that requires a wide angle of view and an interchangeable lens camera.

FIG. 2 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the zoom lens of the present invention. It is the same figure as FIG. 1 of Example 2 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 3 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 6 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 7 of the zoom lens of this invention. It is a figure similar to FIG. 1 of Example 8 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 9 of the zoom lens of this invention. It is a figure similar to FIG. 1 of Example 10 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 11 of the zoom lens of this invention. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 6 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 6 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 7 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 7 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 8 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 8 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 9 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 9 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 10 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 10 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 11 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 11 upon focusing on an object point at infinity. It is a figure which shows correction | amendment of a distortion aberration. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 36 is a rear perspective view of the digital camera of FIG. 35. FIG. 36 is a cross-sectional view of the digital camera of FIG. 35. FIG. 36 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 35.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Aperture stop F ... Optical low pass filter C ... Cover glass I ... Image plane E ... Observer eyeball 12 ... Operation Unit 13 ... Control units 14 and 15 ... Bus 16 ... Imaging drive circuit 17 ... Primary storage memory 18 ... Image processing unit 19 ... Storage medium unit 20 ... Display unit 21 ... Setting information storage memory unit 22 ... Bus 24 ... CDS / ADC unit 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 45 ... Shutter button 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Finder objective optical system 55 ... Erect prism system 55a, 55b, 55c, ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focus Distance change button 62 ... Setting change switch

Claims (26)

A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an image formed by the zoom lens into an electrical signal;
In order from the object side, the zoom lens
A first lens group having negative refractive power;
A second lens group having positive refractive power;
A third lens group having negative refractive power;
And a fourth lens group having positive refractive power,
When a lens block having only two surfaces on the optical axis that are in contact with air, the entrance surface and the exit surface, is defined as a lens component,
The first lens group is composed of one negative lens component in which one negative lens and one positive lens are cemented,
When zooming from the wide-angle end to the telephoto end,
An interval between the first lens group and the second lens group is narrowed,
The interval between the second lens group and the third lens group changes,
The distance between the third lens group and the fourth lens group changes,
Imaging device that satisfies the conditions below.
-1.2 <Hf2 / Y <-0.7 (1)
30 <(νdL1n−νdL1p) <50 (3)
However,
Hf2 is the distance from the object-side lens surface of the second lens group on the optical axis to the front principal point of the second lens group,
The sign is a negative sign when the front principal point is closer to the object side than the second lens group,
Y is the maximum image height within the possible effective imaging area
νdL1n is the Abbe number of the negative lens in the first lens group,
νdL1p is the Abbe number of the positive lens in the first lens group,
It is. A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an image formed by the zoom lens into an electrical signal;
The zoom lens
From the object side,
A first lens group having negative refractive power;
A second lens group having positive refractive power;
A third lens group having negative refractive power;
It consists of a fourth lens group with positive refractive power,
When a lens block having only two surfaces on the optical axis that are in contact with air, the entrance surface and the exit surface, is defined as a lens component,
The first lens group is composed of one negative lens component in which one negative lens and one positive lens are cemented,
The second lens group includes one positive lens and one negative lens in order from the object side.
When zooming from the wide-angle end to the telephoto end,
An interval between the first lens group and the second lens group is narrowed,
The interval between the second lens group and the third lens group changes,
The distance between the third lens group and the fourth lens group changes,
The imaging device, wherein the second lens group satisfies the following conditions.
-1.2 <Hf2 / Y <-0.7 (1)
However,
Hf2 is the distance from the object-side lens surface of the second lens group on the optical axis to the front principal point of the second lens group,
The sign is a negative sign when the front principal point is closer to the object side than the second lens group,
Y is the maximum image height within the possible effective imaging area
It is. The imaging apparatus according to claim 2 , wherein the following conditional expression is satisfied.
ndL2p> 1.65 (4A)
νdL2p> 40.0 (4B)
νdL2n <30.0 (4C)
However,
ndL2p is the refractive index νdL2p of the d-line of the positive lens in the second lens group, and Abbe number of the positive lens in the second lens group,
νdL2n is the Abbe number of the negative lens in the second lens group,
It is. Imaging device according to any one of claims 1 to 3, characterized by satisfying the following conditional expression.
0.1 <ΣG1d / fw <0.25 (2)
However,
ΣG1d is the thickness of the first lens group on the optical axis,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is. The imaging apparatus according to claim 4 , wherein a lens surface closest to the image side of the first lens group is a concave surface, and the lens surface is an aspherical surface. The imaging apparatus according to claim 5 , wherein the aspheric surface has a negative refractive power that decreases as the lens surface moves away from the optical axis. Imaging device according to any one of claims 1 to 6, characterized in that the material of the positive lens of the first lens group is a resin. The material of the positive lens of the first lens group is energy curable resin, and the negative lens component of the first lens group is obtained by directly molding the positive lens on the lens surface of the negative lens. The imaging apparatus according to claim 7 . Imaging device according to any one of claims 1 to 8, wherein the joint surface of the said positive lens of said first lens group negative lens is an aspherical surface. The second lens group comprises, in order from the object side, a positive lens component having positive refractive power, in any one of claims 1 to 9, characterized in that a negative lens component having a negative refractive power The imaging device described. The second lens group, the first positive lens in order from the object side, the imaging apparatus according to any one of claims 1 to 10, characterized in that a cemented lens of the second positive lens and a negative lens. The second lens group, the imaging device according to any one of claims 1 to 10, characterized in that it consists of one positive lens and one negative lens in order from the object side. The imaging apparatus according to claim 12 , wherein the following conditional expression is satisfied.
ndL2p> 1.65 (4A)
νdL2p> 40.0 (4B)
νdL2n <30.0 (4C)
However,
ndL2p is the refractive index νdL2p of the d-line of the positive lens in the second lens group, and Abbe number of the positive lens in the second lens group,
νdL2n is the Abbe number of the negative lens in the second lens group,
It is. The lens surface on the most object side in the second lens group, the imaging device according to any one of claims 1 to 13, characterized in that an aspherical surface. The third lens group, the imaging device according to any one of claims 1 to 14, characterized in that it consists of one negative lens. The imaging device according to claim 15 , wherein the negative lens in the third lens group has at least one aspheric surface. The imaging device according to claim 15 , wherein the negative lens in the third lens group has an aspheric lens surface on the image plane side. The third lens and the negative lens in the group, the imaging device according to any one of claims 15 Optimum claim 17, wherein the material is a resin. Imaging device according to any one of claims 1 to 18, characterized by satisfying the following conditional expression.
2.2 <{β2 (t) / β2 (w)} / {β3 (t) / β3 (w)} <3.0
... (5)
However,
β2 (t) is the lateral magnification at the telephoto end of the second lens group,
β2 (w) is the lateral magnification at the wide-angle end of the second lens group,
β3 (t) is the lateral magnification at the telephoto end of the third lens group,
β3 (w) is the lateral magnification at the wide-angle end of the third lens group,
It is. The fourth lens group, the imaging device according to any one of claims 1 to 19, characterized in that it consists of one positive lens. The imaging device according to claim 20 , wherein the positive lens in the fourth lens group has at least one aspherical surface. 21. The imaging apparatus according to claim 20 , wherein the positive lens in the fourth lens group has an aspherical lens surface closest to the image plane. Wherein said positive lens of the 4 lens groups, an imaging apparatus according to any one of claims 20 to claim 22, characterized in that the material is a resin. Aperture stop is arranged between the space on the image side from the space on the object side of the second lens group, both the aperture stop of claims 1 to 23, characterized in that moves along with the second lens group An imaging apparatus according to claim 1. When zooming from the wide-angle end to the telephoto end,
The first lens group moves to the object side after moving to the image plane side, reversing the moving direction,
The second lens group moves toward the object side;
The third lens group moves so that the distance from the second lens group is wider at the telephoto end than at the wide-angle end,
25. The imaging apparatus according to claim 24 , wherein the fourth lens group moves to the image plane side at a telephoto end rather than at a wide angle end. When any zoom state in which the focal length of the entire zoom lens system is 0.95 × √ (fw · ft) to 1.05 × √ (fw · ft) is set to the near-near zoom state,
26. The zoom lens according to claim 25 , wherein the first lens group, the second lens group, the third lens group, and the fourth lens group satisfy the following condition in any intermediate zoom state. Imaging device.
−0.6 <Δ1GWS / fw <−0.1 (6)
-4.0 <Δ1GWS / Δ1GST <−0.25 (7)
0.3 <Δ2GWS / Δ2GST <0.95 (8)
-20.0 <Δ3GWS / Δ3GST <0.5 (9)
-0.5 <Δ4GST / Δ4GWS <1.5 (10)
However,
Δ1GWS is a difference in position in the middle zoom state with respect to the position of the first lens group at the wide-angle end,
Δ2GWS is the difference between the position of the second lens group in the middle zoom state with respect to the position at the wide-angle end,
Δ3GWS is the difference in position in the middle zoom state with respect to the position of the third lens group at the wide-angle end,
Δ4GWS is the difference in position in the middle zoom state with respect to the position of the fourth lens group at the wide-angle end,
Δ1GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the first lens group,
Δ2GST is the difference in the position at the telephoto end with respect to the position in the middle zoom state of the second lens group,
Δ3GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the third lens group,
Δ4GST is the difference in position at the telephoto end with respect to the position in the middle zoom state of the fourth lens group,
The sign is a positive sign for the direction toward the object, a negative sign for the direction toward the image,
Δ3GST is a positive value,
Δ4GWS is a negative value,
fw is the focal length of the zoom lens at the wide angle end.

Images