JP5484687B2 - Image pickup apparatus having a zoom lens - Google Patents

Description

  The present invention relates to a zoom lens having a reflecting surface that reflects an optical path. Furthermore, the present invention relates to an image pickup apparatus including such a zoom lens and an image pickup device.

A zoom lens used in an imaging apparatus such as a digital camera or a video camera is required to have high performance, a high zoom ratio, and a small size.
One of the important factors in reducing the size of the imaging apparatus is the thickness of the zoom lens (the thickness of the lens system measured in the direction of the optical axis incident from the subject side).
In order to reduce the thickness of the image pickup apparatus when not in use, a zoom lens of a type in which a lens system is extended from the camera body when used (ON) and stored in the camera body when not used (OFF) is known.

However, this type of zoom lens is disadvantageous in terms of driving time and power consumption because the first lens group is largely extended from the main body of the imaging apparatus when the imaging apparatus is switched from OFF to ON.
On the other hand, there is known a zoom lens in which a reflecting member is arranged in the first lens group closest to the object side and the light path is reflected to reduce the operation when the imaging apparatus is turned on and to reduce the thickness.

For example, as disclosed in JP-A-2006-343622, a first lens unit having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power The imaging device is made thin in the thickness direction while securing a high zoom ratio of about 4 times by arranging a reflecting member that reflects the optical path in the first lens group. Zoom lenses are known.
Further, as disclosed in Japanese Patent Application Laid-Open No. 2006-98962, a first lens group having a negative refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power. By arranging a reflecting member that reflects the optical path in the first lens group, the imaging device is made thin in the thickness direction while securing a high zoom ratio of about 3 times. Zoom lenses are known.

JP 2006-343622 A JP 2006-98962 A

However, the zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2006-343622 has a long optical path after being reflected by the reflecting member. Therefore, when the reflection member reflects the optical path in the height direction of the imaging device, the height direction of the imaging device becomes large.
If the lens group closest to the object side is a positive lens group, the distance from the object side surface of the zoom lens to the entrance pupil becomes long, especially at the wide-angle end. In order to secure the angle of view, it is necessary to increase the thickness of the reflecting member in the first lens group.

The zoom lens disclosed in Japanese Patent Application Laid-Open No. 2006-98962 has a large incident angle when an off-axis chief ray is incident on the image plane at the wide angle end. For this reason, shading due to the large incident angle of the light beam easily occurs due to the characteristics of the image sensor.
Further, the negative refractive power of the fourth lens group is too strong. This makes it difficult to simplify the configuration of the lens group in order to reduce aberrations.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging apparatus advantageous for downsizing by making a zoom lens compact, ensuring a necessary zoom ratio, and ensuring optical characteristics.

In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention includes a zoom lens and an image sensor that is disposed on the image side of the zoom lens and converts an optical image formed by the zoom lens into an electrical signal. Is provided. The zoom lens includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. Have
The zoom lens has an aperture stop between the image side surface of the second lens group and the image side surface of the third lens group,
The zoom lens is a 4 group zoom lens,
During zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group changes,
The distance between the second lens group and the third lens group changes, the distance between the third lens group and the fourth lens group changes, and the second lens group and the third lens group at the telephoto end rather than the wide angle end. The interval of becomes narrower.
The first lens group has a reflecting surface that reflects the optical path, and the fourth lens group satisfies the following condition (1A) .
-100 <fg4 / ihw <-6.0 (1A)
However,
fg4 is the focal length of the fourth lens group,
ihw is the maximum image height at the wide-angle end, and is the maximum value that can be taken when the effective imaging area of the imaging device changes.
And the imaging device of this invention is further provided with the following structures (I) or (II).
(I) The third lens group includes two positive lenses and one negative lens, and at least any two lenses are cemented with each other.
(II) The fourth lens group is disposed on the most image side in the fourth lens group and has a lens satisfying the following conditions (7) and (8).
1.4 <nd (g4i) <1.7 (7)
55.0 <νd (g4i) <100 (8)
However,
nd (g4i) is the d-line refractive index of the most image side lens in the fourth lens group,
νd (g4i) is the Abbe number of the most image side lens in the fourth lens group,
It is.
The technical significance of configurations (I) and (II) will be described later.

As described above, by using both the first lens group and the second lens group as lens groups having negative refractive power, it becomes easy to secure the negative refractive power of the combined system of the first and second lens groups at the wide angle end. This is advantageous for securing the angle of view at the wide-angle end, shortening the optical path length, and reducing shading. In addition, by setting the first lens group to have a negative refractive power, it becomes easy to suppress an excess of the negative refractive power of the second lens group. This makes it easy to reduce aberration fluctuations during zooming.
By changing the distance between the second lens unit having negative refracting power and the third lens unit having positive refracting power, the third lens unit can easily have a main zooming effect. In addition, by changing the distance between the lens groups of the first to fourth lens groups, it becomes easier to adjust the image position while adjusting the aberration and the fluctuation of the pupil position.

A fourth lens unit having a negative refractive power is disposed on the image side of the third lens unit having a positive refractive power. That is, a lens unit having a negative refractive power is arranged on both the object side and the image side of the third lens unit having a positive refractive power. Thereby, the symmetry of refractive power can be made favorable. As a result, it becomes easy to suppress the occurrence of distortion and field curvature more than necessary.
Further, by making the number of lens groups four, it is advantageous for cost reduction while saving the number of lens groups and reducing the size.
At that time, the size of each lens and the position of the exit pupil are adjusted by arranging an aperture stop for determining the size of the axial light beam between the image side surface of the second lens group and the image side surface of the third lens group. It becomes easy to make better.
In the zoom lens of the present invention, the thickness of the zoom lens (the thickness of the lens system measured in the direction of the optical axis incident from the subject side) is reduced by providing the first lens group with a reflecting surface as described above. Is advantageous.
The fourth lens group satisfies the following condition (1), particularly a more preferable condition (1A) .
-100 <fg4 / ihw <-2.5 (1)

Conditional expression (1) specifies a preferable ratio between the negative focal length of the fourth lens group and the image height at the wide-angle end.
The fourth lens group has a function of refracting off-axis rays emitted from the third lens group having positive refractive power in a direction away from the optical axis.
Therefore, the second and third lens groups can be adjusted with respect to the size of the image plane depending on the degree of the negative refractive power of the fourth lens group.

Conditional expression (1) is set to obtain a good image and to reduce the size of the lens system.
Ensuring that the negative refractive power of the fourth lens group is ensured so as not to fall below the lower limit of conditional expression (1), it is advantageous for miniaturization of the second and third lens groups with respect to the image height. Further, by securing the negative refractive power of the fourth lens group, it is possible to improve the symmetry of the refractive power arrangement of the entire zoom lens. Thereby, it becomes easy to reduce the excessive occurrence of curvature of field and distortion.

By appropriately suppressing the negative refractive power of the fourth lens group so as not to exceed the upper limit of conditional expression (1), the angle formed between the off-axis principal ray emitted from the fourth lens group and the optical axis is moderately adjusted. Can be reduced. Therefore, it is easy to finally reduce the incident angle of the off-axis chief ray to the image sensor, and it becomes easy to reduce the influence of shading.
In addition, it is easy to reduce the occurrence of aberrations in the fourth lens group itself, and for example, even with a single lens configuration, there are secondary effects such as reduction in off-axis aberration fluctuations during zooming.

Furthermore,
-40 <fg4 / ihw <-4.5 (1 ')
Furthermore,
-15 <fg4 / ihw <-6.0 (1 ”)
It is more preferable to obtain the above effect.
The lower limit value and / or the upper limit value of the conditional expression that further limits the lower limit value and / or the upper limit value of the basic conditional expression may be used. The same applies to the conditional expressions described below.

Further, the effective imaging area means an area where an image used for display, printing, etc. is formed among images formed on the light receiving surface of the imaging element.
In addition, in order to electrically correct the barrel distortion of the zoom lens at the wide-angle end, an image pickup device that displays and prints the image of the barrel-shaped area on the imaging surface at the wide-angle end by changing it to rectangular image information. In this case, the effective imaging area has a barrel shape.

Further, in the case of an imaging device that can change the effective imaging area at the wide-angle end in the shooting state (for example, an imaging device having a function of arbitrarily changing the aspect ratio), the effective imaging area has an image height among the possible imaging areas. Use the maximum value.
Note that as the imaging device, a digital camera, a mobile phone with a camera, a notebook computer equipped with a video communication camera, or the like can be used.

Moreover, it is preferable to specify any of the following constituent elements in the above-described invention.
The fourth lens group is preferably located on the object side at the telephoto end with respect to the wide angle end, and satisfies the following conditional expression.
1.01 <βg4 (t) / βg4 (w) <2.0 (2)
However,
βg4 (w) is the lateral magnification of the fourth lens group at the wide-angle end,
βg4 (t) is the lateral magnification of the fourth lens group at the telephoto end,
It is.

  By moving the fourth lens group as described above, the fourth lens group can have a zooming function. Thereby, the zooming burden of the third lens group can be reduced, which is advantageous in securing the optical performance and zooming ratio.

Conditional expression (2) specifies a preferable zoom ratio of the fourth lens group.
It is preferable not to fall below the lower limit of conditional expression (2) to ensure the zooming function of the fourth lens group.
The upper limit of conditional expression (2) is not exceeded, the zooming burden on the fourth lens group is reduced, and the amount of movement of the fourth lens group is prevented from becoming too large. This is preferable from the viewpoints of reducing fluctuations in off-axis aberrations, downsizing, and reducing manufacturing errors.

Furthermore,
1.02 <β4 (t) / β4 (w) <1.8 (2 ')
Furthermore,
1.03 <β4 (t) / β4 (w) <1.5 (2 ”)
It is more preferable to obtain the above effect.

In addition, it is preferable that the fourth lens group satisfies the following conditions.
-0.35 <Dg4 / fg4 <-0.0005 (3)
Here, Dg4 is the thickness on the optical axis from the object side surface to the image side surface of the fourth lens group.

Conditional expression (3) is a conditional expression that specifies a preferable relationship between the length on the optical axis of the fourth lens group and the focal length.
By making it not fall below the lower limit of the conditional expression (3), it is advantageous for reducing the cost of the lens member. By keeping the thickness of the fourth lens group moderate so as not to exceed the upper limit, it becomes easy to refract off-axis rays without difficulty in terms of durability.

Furthermore,
-0.3 <Dg4 / fg4 <-0.005 (3 ')
Furthermore,
-0.2 <Dg4 / fg4 <-0.01 (3 ")
It is preferable to obtain the above effects.

In addition, it is preferable that the zoom lens satisfies the following conditions.
0.5 <enp (w) / fw <1.8 (4)
However,
enp (w) is the distance on the optical axis from the object-side refractive surface of the first lens unit to the entrance pupil at the wide-angle end,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is.

In the zoom lens of the present invention in which the lens unit closest to the object side has a reflecting surface, the thickness of the zoom lens is greatly influenced by the length from the surface closest to the object side of the first lens unit to the reflecting surface.
In order to reduce this length, it is preferable that the entrance pupil is positioned as close to the object side as possible, and the height of the light beam in the first lens group is kept low.
However, in order to dispose the entrance pupil from the object side, the negative refractive power of the second lens group is increased, or the principal point of the second lens group is set from the object side. For this reason, the influence on various aberrations is increased. For this reason, it is preferable to appropriately set the position of the exit pupil and to satisfactorily balance downsizing and optical performance.

Conditional expression (4) is a preferable condition for that purpose.
By making sure that the lower limit of conditional expression (4) is not exceeded, it becomes easy to improve the aberration balance.
By making sure that the upper limit of conditional expression (4) is not exceeded, it is more advantageous for making the imaging device thinner.

Furthermore
0.7 <enp (w) / fw <1.5 (4 ')
Or even
1.0 <enp (w) / fw <1.3 (4 ”)
More preferably.

In addition, it is preferable that the first lens group and the fourth lens group satisfy the following conditions.
0.001 <fg4 / fg1 <30.0 (5)
Here, fg1 is the focal length of the first lens group.

Conditional expression (5) specifies a preferable focal length ratio between the first lens group and the fourth lens group.
By making sure that the lower limit of conditional expression (5) is not exceeded and the upper limit is not exceeded, the symmetry of the refractive power arrangement of the first lens group and the fourth lens group becomes even better, and distortion, field curvature, etc. Aberration can be further reduced, and it becomes easy to improve the balance between on-axis and off-axis aberrations.

Furthermore,
0.01 <fg4 / fg1 <5.0 (5 ')
Or even
0.3 <fg4 / fg1 <1.3 (5 ”)
More preferably.

The first lens group preferably includes a reflecting prism having a reflecting surface, an object-side refracting surface, and an image-side refracting surface, and the total number of reflecting surfaces reflecting the optical axis in the zoom lens is preferably 1.
By making the total number of reflecting members one, it becomes possible to construct a zoom lens without enlarging the entire length more than necessary. Constructing the reflecting member with a prism is advantageous in securing the optical path length at a low cost.

The first lens group includes a reflecting prism having a reflecting surface, an object-side refracting surface, and an image-side refracting surface,
The reflecting prism preferably satisfies the following conditions.
0.5 <Dpr / fw <2.0 (6)
However,
Dpr is the optical path length along the optical axis from the object side refractive surface to the image side refractive surface of the reflecting prism,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is.

Conditional expression (6) is a preferable condition for reasonably disposing the prism in the first lens group when a prism that reflects the optical axis is used in the first lens group.
By making sure that the lower limit of conditional expression (6) is not exceeded, it becomes easy to ensure the optical path length of the prism.
By avoiding exceeding the upper limit of conditional expression (6), it is advantageous for downsizing of the prism.

Furthermore,
0.7 <Dp / fw <1.5 (6 ')
Furthermore,
0.8 <Dp / fw <1.3 (6 ”)
More preferably.

The first lens group includes a reflecting prism having a reflecting surface, an object-side refracting surface, and an image-side refracting surface,
The reflecting prism preferably satisfies the following conditions.
1.70 <nd (pr) <2.3 (10)
Here, nd (pr) is the d-line refractive index of the reflecting prism in the first lens group.

Conditional expression (10) specifies a preferable refractive index of the reflecting prism in the first lens group. If it is within the range of conditional expression (10), it will be advantageous to ensure a sufficient optical path length without causing unnecessary costs.
By ensuring the refractive index of the reflecting prism so as not to fall below the lower limit of the conditional expression (10), it becomes easy to secure the optical path length while suppressing the enlargement of the reflecting prism.
Avoiding exceeding the upper limit of conditional expression (10) is advantageous in reducing the cost of the reflecting prism.

Furthermore,
1.80 <nd (pr) <2.1 (10 ')
Furthermore,
1.88 <nd (pr) <2.0 (10 ”)
It is more preferable to obtain the above effect.

  In zooming from the wide-angle end to the telephoto end, the first lens unit is fixed, the second lens unit is moved, and the third lens unit is moved to be located closer to the object side at the telephoto end than at the wide-angle end. It is preferable to do.

This eliminates the need for a mechanism for driving the first lens group, and contributes to a reduction in the thickness of the zoom lens. Furthermore, it is advantageous when performing dustproof / dripproofing of the image pickup apparatus.
The second lens group having a negative refractive power can have the role of a compensator. Furthermore, the third lens group having positive refractive power can have a variator role. This is advantageous in securing a zoom ratio and shortening the optical path length.

In zooming from the wide-angle end to the telephoto end, it is preferable that the second lens group first reverses the moving direction to the object side after moving to the image side.
This is advantageous for shortening the optical path length after the reflecting surface while securing the zooming effect by the movement of the third lens group.

In addition, it is preferable that the fourth lens group moves to the image side during a focusing operation from a long distance object to a short distance object.
In the zoom lens used in the imaging apparatus of the present invention, the second lens group and the fourth lens group can be a focusing lens group.
By arranging the focusing lens group on the image side of the reflecting surface, there is no change in the thickness during focusing, which is suitable for thinning.
The fourth lens group is preferable to the second lens group because it is easier to secure a moving space for focusing.

Further, it is preferable that the third lens group includes two positive lenses and one negative lens, and at least one of the two lenses is cemented with each other.
The third lens group has at least one cemented surface, and is composed of two positive lenses and one negative lens, so that axial chromatic aberration and spherical aberration can be favorably corrected particularly at the telephoto end. It becomes possible. By not increasing the number of lenses, it is advantageous in terms of cost. Conversely, securing three lenses is advantageous for reducing spherical aberration, particularly at the telephoto end.

The second lens group is composed of two lenses of a negative lens and a positive lens in order from the object side, and it is preferable that the negative lens and the positive lens are cemented with each other.
Constructing the second lens group in order from the object side with a cemented lens of a negative lens and a positive lens is advantageous for favorably correcting the lateral chromatic aberration particularly at the wide angle end.

The fourth lens group is preferably composed of two or less lenses.
This is advantageous for cost reduction. Furthermore, if the fourth lens group is composed of one negative lens, it is more advantageous for cost reduction.

In addition, it is preferable that the fourth lens group includes a negative lens that is disposed on the most image side in the fourth lens group and satisfies the following conditions.
1.4 <nd (g4i) <1.7 (7)
55.0 <νd (g4i) <100 (8)
However,
nd (g4i) is the d-line refractive index of the most image side lens in the fourth lens group,
νd (g4i) is the Abbe number of the most image side lens in the fourth lens group,
It is.

Conditional expressions (7) and (8) specify the preferable refractive index and Abbe number of the most image-side lens in the fourth lens group.
In the zoom lens used in the image pickup apparatus of the present invention, if the most image side lens in the fourth lens group has a negative refractive power, it is advantageous for miniaturization. This negative lens is preferably made of a low dispersion material.
The use of a negative lens within the range of conditional expression (8) is particularly advantageous for reducing lateral chromatic aberration.
Using a low-dispersion negative lens so as not to fall below the lower limit of conditional expression (8) is advantageous in reducing lateral chromatic aberration. By not exceeding the upper limit of conditional expression (8), the cost of the lens material can be easily suppressed.
By avoiding falling below the lower limit of conditional expression (7), it becomes easy to ensure sufficient refractive power even if the curvature is suppressed, which is advantageous in reducing off-axis aberrations. By not exceeding the upper limit of the conditional expression (7), it is advantageous for reducing the cost of the low-dispersion glass material that satisfies the conditional expression (8).

In addition, it is preferable that the zoom lens used in the present invention satisfies the following conditional expression.
1.8 <ft / fw <6.5 (9)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
ft is the focal length of the entire zoom lens system at the telephoto end,
It is.

It is preferable to ensure the zoom ratio so as not to fall below the lower limit of conditional expression (9).
By suppressing the zoom ratio so as not to exceed the upper limit of the conditional expression (9), it is preferable because the number of lenses can be suppressed, and the compactness, low cost, and optical performance can be more easily maintained.

Moreover, it is preferable that the imaging apparatus of the present invention includes an image conversion unit that converts an electrical signal including distortion by a zoom lens into an image signal in which distortion is corrected by image processing.
Thereby, distortion aberration in the zoom lens can be allowed, which is advantageous for further miniaturization of the zoom lens.

More preferably, the imaging apparatus of the present invention includes an image conversion unit that converts an electrical signal including lateral chromatic aberration caused by a zoom lens into an image signal in which lateral chromatic aberration is corrected by image processing.
Thereby, the chromatic aberration of magnification of the zoom lens can be allowed, which is advantageous for reducing the cost of the lens material and reducing the number of lenses.

Moreover, it is more preferable that the above-described inventions satisfy a plurality at the same time.
Each conditional expression is a value when the zoom lens has a focusing function, in a state where the farthest distance is in focus.

  It is more preferable that a plurality of the above-described inventions are arbitrarily satisfied at the same time. For each conditional expression, only the upper limit value or lower limit value of the numerical range of the more limited conditional expression may be limited. Further, the above-described configurations may be arbitrarily combined.

  According to the present invention, it is possible to provide an imaging apparatus advantageous for downsizing by making the zoom lens compact, ensuring a necessary zoom ratio, and ensuring optical characteristics.

  Embodiments of a zoom lens and an imaging apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  Examples 1 to 9 of the zoom lens according to the present invention will be described below. FIGS. 1 to 9 show lens cross sections of the wide-angle end (a), the intermediate focal length state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 9, respectively. 1 to 9, 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, and the wavelength range is limited to limit infrared light. The parallel flat plate constituting the coated low-pass filter is indicated by F, the parallel flat plate of the cover glass of the electronic image sensor is indicated by C, and the image plane is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action.

  In each embodiment, the aperture stop S moves integrally with the third lens group G3. All of the numerical data is data in a state where an object at infinity is focused. The unit of length of each numerical value is mm, and the unit of angle is ° (degree). In any of the embodiments, focusing is performed by moving the lens group closest to the image side. That is, the focusing operation from a long distance to a short distance is performed by moving the fourth lens group to the image side. Further, the zoom data are values at the wide-angle end (WE), the intermediate zoom state (ST) defined in the present invention, and the telephoto end (TE).

  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, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes an optical path bending prism having a concave surface on the object side and a biconvex positive lens.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 is composed of a negative meniscus lens having a concave surface directed toward the object side.

An aspheric surface is
The object side surface of the optical path bending prism of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive lens of the second lens group G2,
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
The fourth lens group G4 is used for seven surfaces, ie, the object side surface of the negative meniscus lens having a concave surface facing the object side.

  As shown in FIG. 2, the zoom lens of Example 2 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes an optical path bending prism having a concave surface on the object side and a biconvex positive lens.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 is composed of a negative meniscus lens having a concave surface directed toward the object side.

An aspheric surface is
The object side surface of the optical path bending prism of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive lens of the second lens group G2,
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
The fourth lens group G4 is used for seven surfaces, ie, the object side surface of the negative meniscus lens having a concave surface facing the object side.

  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, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes an optical path bending prism having a concave surface on the object side and a biconvex positive lens.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 includes a biconvex positive lens and a negative meniscus lens having a concave surface directed toward the object side.

An aspheric surface is
The object side surface of the optical path bending prism of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive lens of the second lens group G2,
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
The fourth lens group G4 is used for seven surfaces, ie, the object side surface of the negative meniscus lens having a concave surface facing the object side.

  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, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes an optical path bending prism having a concave surface on the object side and a biconvex positive lens.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 includes a biconvex positive lens and a biconcave negative lens.

An aspheric surface is
The object side surface of the optical path bending prism of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive lens of the second lens group G2,
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
It is used for seven surfaces, which are the object side surface of the biconcave negative 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, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes an optical path bending prism having a concave surface on the object side, and a positive meniscus lens having a concave surface on the object side.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 includes a positive meniscus lens having a concave surface directed toward the object side, and a negative meniscus lens having a concave surface directed toward the object side.

An aspheric surface is
An object side surface of the optical path bending prism of the first lens group G1, and an object side surface of a positive meniscus lens having a concave surface facing the object side;
The image-side surface of the biconcave negative lens of the second lens group G2, and the image-side surface of the biconvex positive lens;
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
The fourth lens group G4 is used for seven surfaces, ie, the object side surface of the negative meniscus lens having a concave surface facing the object side.

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

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the image side after moving to the object side.

In order from the object side, the first lens group G1 includes a planoconcave negative lens having a concave surface directed toward the image surface side, a prism, and a biconvex positive lens.
The second lens group G2 is composed of a cemented lens of a biconcave negative lens and a biconvex positive lens.
The third lens group G3 includes a cemented lens made up of a positive meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a biconvex positive lens.
The fourth lens group G4 is composed of a negative meniscus lens having a concave surface directed toward the object side.

An aspheric surface is
An image side surface of a plano-concave negative lens with a concave surface facing the image surface side of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive lens of the second lens group G2,
An object-side surface of a positive meniscus lens having a convex surface facing the object side of the third lens group G3, and an image-side surface of a biconvex positive lens;
The fourth lens group G4 is used for seven surfaces, ie, the object side surface of the negative meniscus lens having a concave surface facing the object side.

  As shown in FIG. 7, the zoom lens of Example 7 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes a planoconcave negative lens having a concave surface directed toward the image surface side, a prism, and a biconvex positive lens.
The second lens group G2 includes a cemented lens including a negative meniscus lens having a convex surface directed toward the image side, a biconcave negative lens, and a positive meniscus lens having a convex surface directed toward the object side.
The third lens group G3 is composed of a cemented lens of a positive meniscus lens having a convex surface directed toward the object side, and a negative meniscus lens having a convex surface directed toward the image side.
The fourth lens group G4 is composed of a negative meniscus lens having a convex surface directed toward the image side.

An aspheric surface is
An image side surface of a plano-concave negative lens with a concave surface facing the image surface side of the first lens group G1, and both surfaces of a biconvex positive lens;
An image side surface of a positive meniscus lens having a convex surface facing the object side of the second lens group G2,
Both surfaces of a positive meniscus lens having a convex surface facing the object side of the third lens group G3;
The fourth lens group G4 is used for seven surfaces including the object side surface of a negative meniscus lens having a convex surface facing the image side.

  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, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

In order from the object side, the first lens group G1 includes a planoconcave negative lens having a concave surface directed toward the image surface side, a prism, and a biconvex positive lens.
The second lens group G2 includes a cemented lens including a negative meniscus lens having a convex surface directed toward the image side, a biconcave negative lens, and a positive meniscus lens having a convex surface directed toward the object side.
The third lens group G3 is composed of a cemented lens of a positive meniscus lens having a convex surface directed toward the object side, and a negative meniscus lens having a convex surface directed toward the image side.
The fourth lens group G4 is composed of a negative meniscus lens having a convex surface directed toward the image side.

An aspheric surface is
An image side surface of a plano-concave negative lens with a concave surface facing the image surface side of the first lens group G1, and both surfaces of a biconvex positive lens;
An image side surface of a positive meniscus lens having a convex surface facing the object side of the second lens group G2,
Both surfaces of a positive meniscus lens having a convex surface facing the object side of the third lens group G3;
The fourth lens group G4 is used for seven surfaces including the object side surface of a negative meniscus lens having a convex surface facing the image side.

  As shown in FIG. 9, the zoom lens of Example 9 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 moves along a locus convex toward the image side, the third lens group G3 moves toward the object side, The lens group G4 moves to the object side.

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

An aspheric surface is
An image side surface of a plano-concave negative lens with a concave surface facing the image surface side of the first lens group G1, and both surfaces of a biconvex positive lens;
The image-side surface of the biconvex positive meniscus lens of the second lens group G2,
Both surfaces of a positive meniscus lens having a convex surface facing the object side of the third lens group G3;
The fourth lens group G4 is used for seven surfaces including the object side surface of a negative meniscus lens having a convex surface facing the image side.

Below, the numerical data of each said Example are shown. Symbols are the above, f is the focal length of the entire system, BF is the back focus, f1, f2... Are the focal lengths of the lens groups, IH is the image height, _FNO is the F number, ω is the half field angle, and WE is the wide angle. ST, intermediate focal length state, TE telephoto end, r1, r2..., Radius of curvature of each lens surface, d1, d2..., Spacing between lens surfaces, nd1, nd2. The ratio, νd1, νd2,... Is the Abbe number of each lens. The total lens length described later is obtained by adding back focus to the distance from the lens front surface to the lens final surface. BF (back focus) represents the distance from the last lens surface to the paraxial image plane in terms of air.

  The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ + A ₁₂ y ¹²
Where r is the paraxial radius of curvature, K is the conic coefficient, and A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are the fourth, sixth, eighth, tenth, and twelfth aspheric coefficients, respectively. . In the aspheric coefficient, “e−n” (n is an integer) indicates “10 ⁻ⁿ ”.

Numerical example 1
Unit mm

Surface data Surface number rd nd νd
1 * -9.669 7.20 1.88300 40.76
2 ∞ 0.20
3 * 12.688 1.50 1.80610 40.92
4 * -462.757 Variable
5 -10.258 0.80 1.88300 40.76
6 14.005 1.54 1.82114 24.06
7 * -34.185 variable
8 (Aperture) ∞ -0.50
9 * 4.980 2.30 1.58313 59.38
10 22.870 0.58 1.84666 23.78
11 7.514 2.50 1.59201 67.02
12 * -75.687 variable
13 * -9.866 1.00 1.52542 55.78
14 -18.904 Variable
15 ∞ 0.50 1.53996 59.45
16 ∞ 0.27
17 ∞ 0.50 1.51633 64.14
18 ∞ 0.23
Image surface (light receiving surface)

Aspheric data first surface
K = -6.995, A4 = 8.86364e-05, A6 = -1.36794e-06, A8 = 9.48088e-08, A10 = -1.27868e-09
Third side
K = 0.000, A4 = -8.08906e-04, A6 = 4.52266e-07, A8 = -1.05791e-06
4th page
K = 13073.884, A4 = -1.96823e-04, A6 = -1.48392e-05, A8 = -5.72156e-07, A10 = 4.81467e-09
7th page
K = 0.000, A4 = -1.20746e-04, A6 = 5.92893e-06, A8 = -2.74132e-07, A10 = 1.07999e-08
9th page
K = 0.000, A4 = -2.41925e-04, A6 = 4.71805e-06, A8 = 3.96700e-08
12th page
K = 0.000, A4 = 1.81119e-03, A6 = 8.41610e-05, A8 = 3.96164e-07, A10 = 7.96156e-07
13th page
K = -11.682, A4 = -1.68789e-03, A6 = 5.61511e-05, A8 = -4.53373e-07, A10 = -1.35706e-07

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.31 4.32 6.00
Angle of view 2ω 66.88 37.47 22.04
BF (in air) 5.95 10.45 17.51
Total length (in air) 41.46 41.46 41.46
d4 0.60 3.37 0.60
d7 12.57 5.68 1.50
d12 5.22 4.84 4.72
d14 4.79 9.29 16.35

Group focal length
f1 = -487.12 f2 = -15.65 f3 = 9.54 f4 = -40.83

Numerical example 2
Unit mm

Surface data Surface number rd nd νd
1 * -10.060 7.20 1.88300 40.76
2 ∞ 0.20
3 * 21.209 1.50 1.80610 40.92
4 * -31.550 variable
5 -11.016 0.80 1.88300 40.76
6 13.255 1.54 1.82114 24.06
7 * -39.143 variable
8 (Aperture) ∞ -0.50
9 * 4.970 2.30 1.58313 59.38
10 22.888 0.58 1.84666 23.78
11 7.309 2.50 1.59201 67.02
12 * -200.331 variable
13 * -7.210 1.00 1.49700 81.54
14 -11.462 Variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.35
Image surface (light receiving surface)

Aspheric data first surface
K = -5.778, A4 = 1.53140e-04, A6 = -1.85187e-06, A8 = 8.77509e-08, A10 = -1.31368e-09
Third side
K = 0.000, A4 = -1.04142e-03, A6 = -2.26093e-05, A8 = -1.10204e-06
4th page
K = 0.000, A4 = -5.76267e-04, A6 = -2.99028e-05, A8 = -4.64492e-07, A10 = 9.30735e-09
7th page
K = 0.000, A4 = -9.75685e-05, A6 = 5.99005e-06, A8 = -5.52928e-07, A10 = 2.30371e-08
9th page
K = 0.000, A4 = -2.12306e-04, A6 = 1.61498e-06, A8 = 1.84162e-07
12th page
K = 0.000, A4 = 1.97988e-03, A6 = 3.82461e-05, A8 = 1.14127e-05
13th page
K = -6.478, A4 = -2.11125e-03, A6 = 9.00702e-05, A8 = -3.77657e-06, A10 = 7.39411e-08

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.22 4.26 6.00
Angle of view 2ω 66.79 37.67 22.10
BF (in air) 1.52 6.69 14.32
Total length (in air) 40.75 40.75 40.75
d4 0.60 3.29 0.60
d7 12.14 5.60 1.50
d12 9.38 8.05 7.22
d14 0.90 6.08 13.70


Group focal length
f1 = -1001.62 f2 = -16.19 f3 = 9.88 f4 = -42.42

Numerical Example 3
Unit mm

Surface data Surface number rd nd νd
1 * -10.666 7.20 1.88300 40.76
2 ∞ 0.20
3 * 42.875 1.50 1.80610 40.92
4 * -19.626 variable
5 -10.516 0.80 1.88300 40.76
6 13.808 1.54 1.82114 24.06
7 * -33.671 variable
8 (Aperture) ∞ -0.50
9 * 5.114 2.30 1.58313 59.38
10 23.448 0.58 1.84666 23.78
11 7.427 2.50 1.59201 67.02
12 * -100.639 variable
13 59.530 1.00 1.49700 81.54
14 -56.357 0.70
15 * -9.457 1.20 1.49700 81.54
16 -54.366 Variable
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.32
Image surface (light receiving surface)

Aspheric data first surface
K = -5.642, A4 = 1.74468e-04, A6 = -9.25278e-07, A8 = 3.88088e-08, A10 = -7.40724e-10
Third side
K = 0.000, A4 = -1.27036e-03, A6 = -3.11260e-05, A8 = -8.83439e-07
4th page
K = 0.000, A4 = -8.02474e-04, A6 = -3.16970e-05, A8 = -9.15728e-08, A10 = 1.44356e-09
7th page
K = 0.000, A4 = -8.79701e-05, A6 = 1.93385e-06, A8 = -2.39948e-07, A10 = 1.33126e-08
9th page
K = 0.000, A4 = -1.80618e-04, A6 = 4.46534e-07, A8 = 3.40266e-07
12th page
K = 0.000, A4 = 1.77865e-03, A6 = 3.53295e-05, A8 = 8.80257e-06
15th page
K = -11.971, A4 = -1.77410e-03, A6 = 9.02388e-05, A8 = -4.31984e-06, A10 = 9.59109e-08

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.18 4.24 6.00
Angle of view 2ω 66.74 37.66 22.10
BF (in air) 1.62 6.90 14.52
Total length (in air) 41.08 41.08 41.08
d4 0.60 3.23 0.60
d7 11.82 5.51 1.50
d12 8.02 6.42 5.44
D16 1.03 6.31 13.93


Group focal length
f1 = -1000.03 f2 = -16.25 f3 = 10.01 f4 = -39.56

Numerical Example 4
Unit mm

Surface data Surface number rd nd νd
1 * -11.115 7.40 1.90366 31.32
2 ∞ 0.40
3 * 128.034 1.50 1.75520 27.51
4 * -17.211 variable
5 -10.244 0.80 1.88300 40.76
6 18.146 1.54 1.82114 24.06
7 * -26.128 variable
8 (Aperture) ∞ -0.50
9 * 5.441 2.30 1.58313 59.38
10 35.722 0.58 1.84666 23.78
11 8.821 2.50 1.59201 67.02
12 * -84.061 variable
13 74.330 1.60 1.49700 81.54
14 -9.800 0.70
15 * -6.800 0.60 1.53996 59.46
16 1315.793 Variable
17 ∞ 0.86 1.53996 59.45
18 ∞ 0.27
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.36
Image surface (light receiving surface)

Aspheric data first surface
K = -6.463, A4 = 1.14372e-04, A6 = 1.27139e-06, A8 = 7.72338e-09, A10 = -5.79803e-10
Third side
K = 0.000, A4 = -1.56736e-03, A6 = -3.43864e-05, A8 = -1.16280e-06
4th page
K = 0.000, A4 = -1.05374e-03, A6 = -3.06515e-05, A8 = -2.23376e-07, A10 = 3.46638e-09
7th page
K = 0.000, A4 = -5.65781e-05, A6 = 5.12392e-07, A8 = -1.28807e-07, A10 = 9.30988e-09
9th page
K = 0.000, A4 = -1.19217e-04, A6 = 9.45301e-07, A8 = 3.71159e-07
12th page
K = 0.000, A4 = 1.46563e-03, A6 = 2.40652e-05, A8 = 5.48591e-06
15th page
K = -7.143, A4 = -2.70642e-03, A6 = 1.40791e-04, A8 = -7.41075e-06, A10 = 1.86143e-07

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.24 4.32 6.00
Angle of view 2ω 66.83 37.78 22.13
bf (in air) 4.42 9.85 17.19
Total length (in air) 43.13 43.13 43.13
d4 0.60 3.43 0.60
d7 12.51 5.51 1.50
d12 6.18 4.92 4.41
d16 2.90 8.33 15.67

Group focal length
f1 = -87.54 f2 = -18.26 f3 = 10.55 f4 = -52.58

Numerical Example 5
Unit mm

Surface data Surface number rd nd νd
1 * -11.583 7.40 1.90366 31.32
2 ∞ 0.40
3 * -436.681 1.50 1.75520 27.51
4 * -14.913 Variable
5 -10.244 0.80 1.88300 40.76
6 20.030 1.54 1.82114 24.06
7 * -25.471 variable
8 (Aperture) ∞ -0.50
9 * 5.440 2.30 1.58313 59.38
10 36.600 0.58 1.84666 23.78
11 8.535 2.50 1.59201 67.02
12 * -34.209 variable
13 -61.840 1.60 1.49700 81.54
14 -16.411 0.70
15 * -7.459 0.60 1.53996 59.46
16 -58.332 Variable
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.34
Image surface (light receiving surface)

Aspheric data first surface
K = -7.120, A4 = 6.91729e-05, A6 = 3.81177e-07, A8 = 8.49052e-08, A10 = -1.93952e-09
Third side
K = 0.000, A4 = -1.64212e-03, A6 = -3.39862e-05, A8 = -1.11973e-06
4th page
K = 0.000, A4 = -1.12011e-03, A6 = -2.95328e-05, A8 = -4.30068e-08, A10 = -3.29865e-09
7th page
K = 0.000, A4 = -5.13040e-05, A6 = -1.65894e-06, A8 = 1.31797e-08, A10 = 8.57360e-09
9th page
K = 0.000, A4 = -1.71801e-04, A6 = -7.56342e-07, A8 = 5.13068e-07
12th page
K = 0.000, A4 = 1.37457e-03, A6 = 1.95338e-05, A8 = 5.13111e-06
15th page
K = -8.443, A4 = -2.51401e-03, A6 = 1.13928e-04, A8 = -4.62845e-06, A10 = 5.61581e-09

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.09 4.23 6.00
Angle of view 2ω 66.63 37.64 22.07
BF (in air) 2.04 6.99 14.02
Total length (in air) 41.13 41.13 41.13
d4 0.60 3.14 0.60
d7 11.48 5.26 1.50
d12 7.60 6.32 5.59
d16 1.43 6.38 13.42


Group focal length
f1 = -107.88 f2 = -18.68 f3 = 9.93 f4 = -25.00

Numerical Example 6
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.70 1.85 135 40.10
2 * 8.726 1.27
3 ∞ 6.10 1.88300 40.76
4 ∞ 0.20
5 * 39.249 1.50 1.80139 45.45
6 * -20.113 variable
7 -14.379 0.80 1.88300 40.76
8 10.498 1.54 1.82114 24.06
9 * -115.856 variable
10 (Aperture) ∞ -0.50
11 * 5.585 2.30 1.58313 59.38
12 6.528 0.60 1.84666 23.78
13 4.297 2.50 1.59201 67.02
14 * -231.788 variable
15 * -37.172 1.00 1.52542 55.78
16 -3936.644 Variable
17 ∞ 0.50 1.53996 59.45
18 ∞ 0.27
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.24
Image surface (light receiving surface)

Aspheric data 2nd surface
K = -0.322, A4 = 5.65948e-05, A6 = 4.01499e-06, A8 = -2.16394e-07, A10 = 4.03005e-09
5th page
K = 0.000, A4 = -2.48024e-04, A6 = -7.10601e-06, A8 = -1.45377e-06
6th page
K = 20.718, A4 = -4.65244e-05, A6 = 1.26188e-05, A8 = -2.70762e-06, A10 = 1.11238e-07
9th page
K = 0.000, A4 = 5.80216e-06, A6 = 3.86474e-08, A8 = 1.43464e-08, A10 = 1.16997e-09
11th page
K = 0.000, A4 = -6.65874e-05, A6 = 5.13875e-06, A8 = -4.60090e-08
14th page
K = 0.000, A4 = 1.23863e-03, A6 = 2.47834e-05, A8 = 5.00000e-06
15th page
K = 0.000, A4 = -1.14790e-04, A6 = 3.62905e-05, A8 = -4.29689e-06, A10 = 1.89880e-07

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.61
FNO. 3.45 4.46 6.00
Angle of view 2ω 66.94 37.81 22.05
BF (in air) 10.16 13.51 12.85
Total length (in air) 46.64 46.64 46.64
d6 0.40 3.35 1.58
d9 14.41 6.73 1.80
d14 3.66 5.05 12.41
d16 8.99 12.35 11.69

Group focal length
f1 = -135.45 f2 = -16.73 f3 = 10.78 f4 = -71.43

Numerical Example 7
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.70 1.90366 31.32
2 * 9.474 1.30
3 ∞ 6.10 1.88300 40.80
4 ∞ 0.20
5 * 214.997 1.37 1.80139 45.45
6 * -15.441 variable
7 -14.080 0.70 1.89800 34.01
8 -23.787 0.30
9 -46.122 0.70 1.88300 40.76
10 7.919 1.54 1.82114 24.06
11 * 730.111 variable
12 (Aperture) ∞ -0.50
13 * 6.342 2.34 1.88300 40.80
14 * 8.000 1.00
15 16.989 2.66 1.60738 56.81
16 -5.076 0.60 1.92286 20.88
17 -10.130 Variable
18 * -4.872 2.00 1.49700 81.54
19 -7.000 Variable
20 ∞ 0.40 1.51633 64.14
21 ∞ 0.35
Image surface (light receiving surface)

Aspheric data 2nd surface
K = 0.235, A4 = 1.93221e-04, A6 = 3.57769e-06, A8 = 3.77560e-07, A10 = -1.36353e-08
5th page
K = 0.000, A4 = 4.74769e-04, A6 = 4.43554e-07, A8 = 9.55336e-07
6th page
K = 0.000, A4 = 3.03478e-04, A6 = -5.80636e-06, A8 = 1.15211e-06
11th page
K = 0.000, A4 = -8.91666e-05, A6 = 1.03333e-05, A8 = -8.97361e-07, A10 = 3.17188e-08
13th page
K = 0.000, A4 = 2.27107e-04, A6 = 2.64978e-06, A8 = 8.96538e-07
14th page
K = 0.000, A4 = 9.16289e-04, A6 = 2.65625e-06, A8 = 3.86325e-06, A10 = 3.51954e-09
18th page
K = 0.000, A4 = 3.14352e-04, A6 = -1.45033e-05, A8 = 4.52807e-06, A10 = -2.48295e-07

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.70
FNO. 3.42 4.41 6.00
Angle of view 2ω 68.46 38.40 22.14
BF (in air) 1.76 6.04 12.38
Total length (in air) 45.78 45.78 45.78
d6 0.40 3.46 0.50
d11 12.74 4.99 0.60
d17 9.88 10.29 11.30
d19 1.15 5.43 11.76

Group focal length
f1 = -90.35 f2 = -18.42 f3 = 10.67 f4 = -46.86

Numerical Example 8
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.70 1.90366 31.32
2 * 9.319 1.30
3 ∞ 6.10 1.88300 40.80
4 ∞ 0.20
5 * 76.833 1.37 1.80139 45.45
6 * -19.455 variable
7 -13.947 0.70 1.89800 34.01
8 -23.872 0.30
9 -61.238 0.70 1.88300 40.76
10 7.884 1.54 1.82114 24.06
11 * 1064.449 Variable
12 (Aperture) ∞ -0.50
13 * 6.337 2.34 1.88300 40.80
14 * 8.032 1.00
15 16.358 2.66 1.60738 56.81
16 -5.076 0.60 1.92286 20.88
17 -10.232 variable
18 * -4.811 3.00 1.49700 81.54
19 -7.000 Variable
20 ∞ 0.50 1.51633 64.14
21 ∞ 0.36
Image surface (light receiving surface)

Aspheric data 2nd surface
K = -0.130, A4 = 1.49423e-04, A6 = 3.98047e-06, A8 = 2.85983e-07, A10 = -1.22151e-08
5th page
K = 0.000, A4 = 4.31902e-04, A6 = 1.03352e-06, A8 = 6.40435e-07
6th page
K = 0.000, A4 = 3.01985e-04, A6 = -5.22165e-06, A8 = 8.38311e-07
11th page
K = 0.000, A4 = -9.15326e-05, A6 = 1.09818e-05, A8 = -8.91733e-07, A10 = 3.13179e-08
13th page
K = 0.000, A4 = 2.19372e-04, A6 = 2.60634e-06, A8 = 8.86538e-07
14th page
K = 0.000, A4 = 9.02367e-04, A6 = 5.48721e-07, A8 = 3.95804e-06, A10 = -2.56278e-09
18th page
K = 0.000, A4 = 1.39268e-04, A6 = -8.05906e-06, A8 = 2.76445e-06, A10 = -1.57684e-07

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.70
FNO. 3.49 4.49 6.00
Angle of view 2ω 67.85 38.22 22.08
BF (in air) 1.68 6.42 12.58
Total length (in air) 46.71 46.71 46.71
d6 0.40 3.58 0.50
d11 13.39 5.05 0.61
d17 9.24 9.66 11.01
d19 0.99 5.73 11.89

Group focal length
f1 = -52.45 f2 = -20.08 f3 = 10.58 f4 = -56.78

Numerical Example 9
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.70 1.90366 31.32
2 * 9.671 1.30
3 ∞ 6.10 1.88300 40.80
4 ∞ 0.20
5 * 49.879 1.50 1.80139 45.45
6 * -19.966 Variable
7 -17.951 0.80 1.88300 40.76
8 8.378 1.54 1.82114 24.06
9 * -305.609 variable
10 (Aperture) ∞ -0.50
11 * 6.506 2.30 1.88300 40.80
12 * 8.000 1.00
13 16.763 2.50 1.60738 56.81
14 -5.076 0.60 1.92286 20.88
15 -9.625 Variable
16 * -4.863 1.00 1.49700 81.54
17 -7.000 Variable
18 ∞ 0.50 1.53996 59.45
19 ∞ 0.27
20 ∞ 0.40 1.51633 64.14
21 ∞ 0.31
Image surface (light receiving surface)

Aspheric data 2nd surface
K = 0.024, A4 = 1.70072e-04, A6 = 5.04323e-06, A8 = 1.47597e-07, A10 = -1.76747e-09
5th page
K = 0.000, A4 = 3.90268e-04, A6 = -9.13537e-06, A8 = 1.67246e-06
6th page
K = 0.000, A4 = 2.39852e-04, A6 = -1.57725e-05, A8 = 1.97072e-06
9th page
K = 0.000, A4 = -6.51307e-05, A6 = 1.28635e-05, A8 = -1.34323e-06, A10 = 5.12631e-08
11th page
K = 0.000, A4 = 1.41690e-04, A6 = 2.43034e-06, A8 = 6.60052e-07
12th page
K = 0.000, A4 = 7.51383e-04, A6 = -4.90855e-06, A8 = 3.96495e-06, A10 = -8.30497e-08
16th page
K = 0.000, A4 = 3.49376e-04, A6 = 3.80029e-07, A8 = 1.98719e-06, A10 = -5.63213e-08

Various data
WE ST TE
Image height 3.60 3.60 3.60
Focal length 6.46 10.90 18.70
FNO. 3.37 4.36 6.00
Angle of view 2ω 68.05 38.25 22.11
BF (in air) 2.18 5.90 12.14
Total length (in air) 44.11 44.11 44.11
d6 0.40 3.66 0.99
d9 12.29 4.78 0.60
d15 10.20 10.73 11.34
d17 1.01 4.73 10.97

Group focal length
f1 = -100.00 f2 = -18.57 f3 = 10.61 f4 = -37.94

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 9 are shown in FIGS. In these aberration diagrams, (a) is the wide angle end, (b) is the intermediate state, (c) is the spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) at the telephoto end. ). In each figure, “FIY” indicates the maximum image height.

Next, the values of conditional expressions (1) to (10) in each example will be listed.

The value corresponding to conditional expression 1 here is a state in which imaging without distortion correction is performed.
Example 1 Example 2 Example 3 Example 4 Example 5
(1) fg4 / ihw -11.342 -11.784 -10.989 -14.604 -6.944
(2) βg4 (t) / βg4 (w) 1.240 1.279 1.310 1.233 1.439
(3) Dg4 / fg4 -0.024 -0.024 -0.073 -0.055 -0.116
(4) enp (w) / fw 1.146 1.145 1.146 1.146 1.146
(5) fg4 / fg1 0.084 0.042 0.040 0.601 0.232
(6) Dpr / fw 1.115 1.115 1.115 1.146 1.146
(7) nd (g4i) 1.525 1.497 1.497 1.540 1.540
(8) νd (g4i) 55.777 81.540 81.540 59.460 59.460
(9) ft / fw 2.881 2.881 2.881 2.881 2.881
(10) nd (pr) 1.883 1.883 1.883 1.90366 1.90366

Example 6 Example 7 Example 8 Example 9
(1) fg4 / ihw -19.841 -13.016 -15.773 -10.540
(2) βg4 (t) / βg4 (w) 1.033 1.193 1.155 1.233
(3) Dg4 / fg4 -0.014 -0.043 -0.053 -0.026
(4) enp (w) / fw 1.161 1.161 1.161 1.161
(5) fg4 / fg1 0.527 0.519 1.083 0.379
(6) Dpr / fw 0.944 0.944 0.944 0.944
(7) nd (g4i) 1.525 1.497 1.497 1.497
(8) νd (g4i) 55.777 81.540 81.540 81.540
(9) ft / fw 2.881 2.895 2.895 2.895
(10) nd (pr) 1.883 1.883 1.883 1.883

After distortion correction (the value corresponding to Conditional Expression 1 here is a state in which the effective imaging area at the wide-angle end is barrel-shaped)
Example 1 Example 2 Example 3 Example 4 Example 5
Image height 3.34 3.343 3.347 3.348 3.348
Half angle of view 30.819 30.859 30.891 30.897 30.887
(1) fg4 / ihw -12.2251 -12.6903 -11.8201 -15.7036 -7.46714

Example 6 Example 7 Example 8 Example 9
Image height 3.345 3.302 3.317 3.315
Half angle of view 30.869 31.06 30.96 30.985
(1) fg4 / ihw -21.3538 -14.1907 -17.1188 -11.446

The flare stop is disposed on the object side of the first lens group, between the first and second lens groups, between the second and third lens groups, between the third and fourth lens groups, and between the fourth lens group and the image plane. You may do it. The flare beam may be cut by a frame member that holds the lens in the zoom lens. A member different from the frame may be configured. These frames and members also serve as flare stops.
Also, a flare stop may be printed directly on any of the lenses included in the zoom lens, painted black, or a national color sticker or the like may be adhered.
Further, the shape of the opening 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 harmful light beams but also light beams such as coma flare around the screen may be cut.
Further, it is preferable that at least one surface of the lenses constituting the zoom lens is provided with an antireflection coating.
In order to prevent the occurrence of ghost and flare, it is common practice to apply an antireflection coating to the air contact surface of the lens. On the other hand, the refractive index of the adhesive is sufficiently higher than the refractive index of air on the cemented surface of the cemented lens. For this reason, the reflectance is often the same as or lower than that of a single-layer coating, and it is rare to apply a coating. However, if an anti-reflection coating is also applied to the joint surface, ghosts and flares can be further reduced, and still better images can be obtained. In recent years, high refractive index glass materials have become widespread and have been used extensively in camera optical systems due to their high aberration correction effects. However, when high refractive index glass materials are used as cemented lenses, reflection on the cemented surface is ignored. It becomes impossible. In such a case, it is particularly effective to provide an antireflection coating on the joint surface. The effective usage of the bonding surface coat is disclosed in JP-A-2-27301, JP-A-2001-324676, JP-A-2005-92115, USP7116482, and the like. These documents particularly describe the cemented lens surface coat in the first group of the positive leading zoom lens, and the cemented lens surface in the first lens group of the positive power of the present invention is also disclosed in these documents. Just do it. As the coating material to be used, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , CeO, which have a relatively high refractive index, depending on the refractive index of the base lens and the refractive index of the adhesive. _{2, SnO 2, in 2 O} 3, ZnO, Y 2 O 3 coating material such as a relatively low refractive index of MgF _2, SiO _2, coating materials such as Al ₂ O _3, and appropriately selected, phase condition The film thickness may be set so as to satisfy the above. As a matter of course, the coating on the bonding surface may be a multi-coating as well as the coating on the air contact surface of the lens. By appropriately combining two or more layers of coating materials and film thicknesses, it becomes possible to further reduce the reflectance and control the spectral characteristics and angular characteristics of the reflectance. Needless to say, it is effective to coat the cemented surfaces other than the first lens group based on the same concept.

(Embodiment for electrically correcting aberration)
In the present invention, image recording and display are performed after electrically correcting barrel distortion generated on the wide-angle side of the zoom lens. In the zoom lens of this embodiment, barrel distortion occurs on the wide-angle side on the rectangular photoelectric conversion surface of the image sensor. On the other hand, the occurrence of distortion is suppressed near the intermediate focal length state and at the telephoto end. In order to electrically correct the distortion, the effective imaging area has 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 image height IHw at the wide angle end is set to be smaller than the image height IHs at the intermediate focal length state and the image height IHt at the telephoto end.

In addition, an image conversion unit that converts an electrical signal of an image captured by the zoom lens into an image signal in which a color shift due to magnification chromatic aberration is corrected by image processing is provided. By electrically correcting the chromatic aberration of magnification of the zoom lens, a better image can be obtained. In general, in an electronic still camera, an image of a subject is separated into three primary color images of a first primary color, a second primary color, and a third primary color, and a color image is reproduced by superimposing respective output signals by calculation. I have to.
When the zoom lens has chromatic aberration of magnification, the image of the first primary color is formed at the position where the image of the second primary color and the third primary light is formed, considering the image of the first primary color as a reference. Will deviate from the position. In order to electrically correct the chromatic aberration of magnification of the image, the amount of displacement of the imaging positions of the light of the second primary color and the third primary color with respect to the first primary color is determined for each pixel of the image sensor based on the aberration information of the zoom lens. Find in advance.
Then, coordinate conversion may be performed for each pixel of the captured image so as to correct the amount of deviation from the first primary color. For example, an image composed of output signals of three primary colors of red (R), green (G), and blue (B) will be described. R and B imaging position shifts with respect to G are calculated for each pixel. Then, the coordinate transformation of the captured image is performed so that the deviation from G is eliminated. Thereafter, R and B signals may be output.

  The chromatic aberration of magnification varies depending on the zoom, focus, and aperture value, but for each lens position (zoom, focus, and aperture value), the deviation amounts of the second primary color and the third primary color from the first primary color are stored and retained as correction data. It is desirable to store in the device. Then, this correction data is referred to according to the zoom position. Thereby, it is possible to output the second and third primary color signals in which the deviation between the second and third primary colors with respect to the first primary color signal is corrected.

(Correction of distortion)
By the way, when the zoom lens of the present invention is used, image distortion is digitally corrected electrically. The basic concept for digitally correcting image distortion will be described below.

  For example, as shown in FIG. 19, 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. 19, 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 a radius r ₂ ′ (ω) circumference to be corrected in a direction away from the center of the circle. It is moved to the point Q ₂ of the above.

Here, r ′ (ω) can be expressed as follows.
r ′ (ω) = α · f · tan ω (0 ≦ α ≦ 1)
However,
ω is the subject half angle of view, 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 / (f · tan ω)
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 is electrically corrected, the radius inscribed in the short side of the effective imaging surface centered on 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 (Xi ′, Yj ′) of the movement destination for each pixel (Xi, Yj). When two or more points (Xi, Yj) have moved to the coordinates (Xi ′, Yj ′), the average value of the values possessed by each pixel is taken. If there is no moving point, interpolation may be performed using the values of the coordinates (Xi ′, Yj ′) of some surrounding pixels.

  Such a method is particularly distorted with respect to the optical axis due to manufacturing errors of an optical system and an electronic imaging device in an electronic imaging apparatus having 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 ≦ 0.6Ls
However, Ls is the length of the short side of the effective imaging surface.

Preferably, the radius R satisfies the following conditional expression.
0.3Ls≤R≤0.6Ls
Furthermore, it is most advantageous to make the radius R coincide 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 image quality, but the effect of downsizing can be ensured even if the angle is widened.

The focal length section that needs to be corrected is divided into several focal zones. And approximately near the telephoto end in the divided focal zone,
r ′ (ω) = α · f · 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.

And approximately near the telephoto end in the divided zone,
r ′ (ω) = α · f · 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.

(Digital camera)
The zoom lens of the present invention as described above forms an object image, and the image can be received by an electronic image sensor such as a CCD. The embodiment is illustrated below.

  20 to 22 are conceptual diagrams of structures in which the zoom lens according to the present invention is incorporated in the photographing optical system 141 of the digital camera. 20 is a front perspective view showing the appearance of the digital camera 140, FIG. 21 is a rear perspective view thereof, and FIG. 22 is a cross-sectional view showing the configuration of the digital camera 140. In this example, the digital camera 140 includes a photographing optical system 141 having a photographing optical path 142, a finder optical system 143 having a finder optical path 144, a shutter 145, a flash 146, a liquid crystal display monitor 147, and the like. When the shutter 145 disposed in the position is pressed, photographing is performed through the photographing optical system 141, for example, the optical path bending zoom lens according to the first embodiment in conjunction therewith. An object image formed by the photographing optical system 141 is formed on the imaging surface of the CCD 149 through a near-infrared cut filter and an optical low-pass filter F. The object image received by the CCD 149 is displayed as an electronic image on a liquid crystal display monitor 147 provided on the back of the camera via the processing means 151. Further, the processing means 151 is connected to a recording means 152 so that a photographed electronic image can be recorded. The recording unit 152 may be provided separately from the processing unit 151, or may be configured to perform recording / writing electronically using a flexible disk, a memory card, an MO, or the like. Further, instead of the CCD 149, a silver salt camera in which a silver salt film is arranged may be configured.

  Further, a finder objective optical system 153 is disposed on the finder optical path 144. The object image formed by the finder objective optical system 153 is formed on the field frame 157 of the Porro prism 155 that is an image erecting member. Behind this polyprism 155, an eyepiece optical system 159 for guiding an erect image to the observer eyeball E is disposed. Cover members 150 are disposed on the incident side of the photographing optical system 141 and the finder objective optical system 153 and on the exit side of the eyepiece optical system 159, respectively.

  The digital camera 140 configured in this manner is a zoom lens having a high zoom ratio and a high optical performance of the photographing optical system 141 of about 3 times. Can be realized.

  In addition, in the example of FIG. 22, although a parallel plane board is arrange | positioned as the cover member 150, you may omit.

(Internal circuit configuration)
FIG. 23 is a block diagram showing the internal circuitry of the main part of the digital camera 140. In the following description, the processing means includes, for example, the CDS / ADC unit 124, the temporary storage memory 117, the image processing unit 118, and the like, and the storage means includes, for example, the storage medium unit 119.

  As shown in FIG. 23, the digital camera 140 is connected to the operation unit 112, the control unit 113 connected to the operation unit 112, and the control signal output port of the control unit 113 via buses 114 and 115. An imaging drive circuit 116, a temporary storage memory 117, an image processing unit 118, a storage medium unit 119, a display unit 120, and a setting information storage memory unit 121 are provided.

  The temporary storage memory 117, the image processing unit 118, the storage medium unit 119, the display unit 120, and the setting information storage memory unit 121 are configured so that data can be input or output with each other via the bus 122. In addition, a CCD 149 and a CDS / ADC unit 124 are connected to the imaging drive circuit 116.

  The operation unit 112 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 113 is a central processing unit composed of, for example, a CPU and the like. The control unit 113 includes a program memory (not shown) and is input from the camera user via the operation unit 112 according to a program stored in the program memory. This is a circuit that controls the entire digital camera 140 in response to an instruction command.

  The CCD 149 receives an object image formed through the photographing optical system 141 according to the present invention. The CCD 149 is an image pickup element that is driven and controlled by the image pickup drive circuit 116, converts the light amount of each pixel of the object image into an electrical signal, and outputs the electric signal to the CDS / ADC unit 124.

  The CDS / ADC unit 124 amplifies the electric signal input from the CCD 149 and performs analog / digital conversion, and temporarily stores the raw video data (Bayer data, hereinafter referred to as RAW data) that has just been subjected to the amplification and digital conversion. This is a circuit for outputting to the storage memory 117.

  The temporary storage memory 117 is a buffer made of, for example, SDRAM or the like, and is a memory device that temporarily stores the RAW data output from the CDS / ADC unit 124. The image processing unit 118 reads out the RAW data stored in the temporary storage memory 117 or the RAW data stored in the storage medium unit 119, and performs various corrections including distortion correction based on the image quality parameter designated from the control unit 113. It is a circuit that performs image processing electrically.

  The recording medium unit 119 detachably mounts a card-type or stick-type recording medium made of, for example, a flash memory, and RAW data transferred from the temporary storage memory 117 to the card-type or stick-type flash memory. This is a control circuit of an apparatus for recording and holding image data processed by the image processing unit 118.

  The display unit 120 includes a liquid crystal display monitor, and is a circuit that displays an image, an operation menu, and the like on the liquid crystal display monitor. The setting information storage memory unit 121 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 112 among the image quality parameters read from the ROM unit. RAM section is provided. The setting information storage memory unit 121 is a circuit that controls input and output to these memories.

  In the digital camera 140 configured in this way, the imaging optical system 141 has a sufficiently wide angle range and a compact configuration according to the present invention, and 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.

  Next, FIG. 24 shows a telephone which is an example of an information processing apparatus in which the bending variable magnification optical system of the present invention is incorporated as a photographing optical system, particularly a portable telephone which is convenient to carry. 24A is a front view of the mobile phone 400, FIG. 24B is a side view, and FIG. 24C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 24A to 24C, the mobile phone 400 includes a microphone unit 401 that inputs an operator's voice as information, a speaker unit 402 that outputs the voice of the other party, and an operator who receives information. An input dial 403 for inputting information, a monitor 404 for displaying information such as a photographed image and a telephone number of the operator and the other party, a photographing optical system 405, an antenna 406 for transmitting and receiving communication radio waves, and an image And processing means (not shown) for processing information, communication information, input signals, and the like. Here, the monitor 404 is a liquid crystal display element. In the drawing, the arrangement positions of the respective components are not particularly limited to these. The photographing optical system 405 includes an objective lens 212 which is a bending variable magnification optical system (abbreviated in the drawing) according to the present invention disposed on a photographing optical path 407, and an image sensor chip 162 that receives an object image. . These are built in the mobile phone 400.

  Here, an optical low-pass filter F is additionally attached on the image sensor chip 149 to be integrally formed as an image pickup unit 160, and can be fitted and attached to the rear end of the lens frame 213 of the objective lens 212 with one touch. Therefore, it is not necessary to align the center of the objective lens 212 and the image sensor chip 162 and to adjust the surface interval, and the assembly is simple. Further, a cover glass 214 for protecting the objective lens 212 is disposed at the tip (not shown) of the lens frame 213. The zoom lens driving mechanism in the lens frame 213 is not shown.

  The object image received by the imaging element chip 149 is input to a processing unit (not shown) through a terminal, and is displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. Further, when transmitting an image to a communication partner, the processing means includes a signal processing function for converting information of an object image received by the image sensor chip 149 into a signal that can be transmitted.

  As described above, the present invention is suitable for a compact imaging device by making the zoom lens to be used compact, ensuring a necessary zoom ratio, and ensuring optical characteristics.

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. 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. 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 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 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 9 upon focusing on an object point at infinity. It is a figure explaining correction | amendment of a distortion aberration. It is a front perspective view which shows the external appearance of the digital camera incorporating the optical path bending zoom lens by this invention. It is a rear perspective view of the digital camera. It is sectional drawing of the said digital camera. It is a block diagram of the internal circuit of the main part of the digital camera. It is a figure which shows the structure of the mobile telephone incorporating the optical path bending zoom lens by this invention.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Aperture stop F ... Low pass filter C ... Cover glass P ... Prism I ... Image plane 112 ... Operation part 113 ... Control Section 114 ... Bus 115 ... Bus 116 ... Imaging drive circuit 117 ... Temporary storage memory 118 ... Image processing section 119 ... Storage medium section 120 ... Display section 121 ... Setting information storage memory section 122 ... Bus 124 ... CDS / ADC section 140 ... Digital Camera 141 ... Shooting optical system 142 ... Shooting optical path 143 ... Viewfinder optical system 144 ... Viewfinder optical path 145 ... Shutter button 146 ... Flash 147 ... Liquid crystal display monitor 149 ... CCD
150 ... cover member 151 ... processing means 152 ... recording means 153 ... finder objective optical system 155 ... erecting prism 157 ... field frame 159 ... eyepiece optical system 400 ... mobile phone 402 ... speaker unit 403 ... input dial 404 ... monitor 405 ... Imaging optical system 406 ... Antenna 407 ... Imaging optical path 162 ... Imaging element chip 160 ... Imaging unit 213 ... Frame 212 ... Objective lens 214 ... Cover glass 166 ... Terminal

Claims (17)

A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an optical image formed by the zoom lens into an electrical signal;
In order from the object side to the image side, the zoom lens
A first lens unit having negative refractive power;
A second lens unit having negative refractive power,
A third lens unit having positive refractive power,
A fourth lens unit having negative refractive power;
The zoom lens has an aperture stop between the image side surface of the second lens group and the image side surface of the third lens group,
The zoom lens is a four-group zoom lens;
When zooming from the wide-angle end to the telephoto end,
The distance between the first lens group and the second lens group changes,
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 distance between the second lens group and the third lens group is narrower at the telephoto end than at the wide-angle end,
The first lens group has a reflecting surface that reflects the optical path;
The third lens group includes two positive lenses and one negative lens, and at least any two lenses are bonded to each other.
An image pickup apparatus having a zoom lens, wherein the fourth lens group satisfies the following conditions.
-100 <fg4 / ihw <-6.0 (1A)
However,
fg4 is the focal length of the fourth lens group,
ihw is the maximum image height at the wide-angle end, and is the maximum value that can be taken when the effective imaging region changes. A zoom lens,
An image sensor that is disposed on the image side of the zoom lens and converts an optical image formed by the zoom lens into an electrical signal;
The zoom lens
From the object side to the image side,
A first lens unit having negative refractive power;
A second lens unit having negative refractive power,
A third lens unit having positive refractive power,
A fourth lens unit having negative refractive power;
The zoom lens has an aperture stop between the image side surface of the second lens group and the image side surface of the third lens group,
The zoom lens is a four-group zoom lens;
When zooming from the wide-angle end to the telephoto end,
The distance between the first lens group and the second lens group changes,
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 distance between the second lens group and the third lens group is narrower at the telephoto end than at the wide-angle end,
The first lens group has a reflecting surface that reflects the optical path;
The fourth lens group satisfies the following condition (1A):
An image pickup apparatus having a zoom lens, wherein the fourth lens group includes a lens that is disposed closest to the image side in the fourth lens group and satisfies the following conditions (7) and (8).
-100 <fg4 / ihw <-6.0 (1A)
1.4 <nd (g4i) <1.7 (7)
55.0 <νd (g4i) <100 (8)
However,
fg4 is the focal length of the fourth lens group,
ihw is the maximum image height at the wide-angle end, and the maximum value in the possible range when the effective imaging area changes,
nd (g4i) is the d-line refractive index of the most image side lens in the fourth lens group,
νd (g4i) is the Abbe number of the most image side lens in the fourth lens group,
It is. The fourth lens group is located on the object side at the telephoto end with respect to the wide angle end,
The imaging apparatus according to claim 1, wherein the following condition is satisfied.
1.01 <βg4 (t) / βg4 (w) <2.0 (2)
However,
βg4 (w) is the lateral magnification of the fourth lens group at the wide angle end when focusing on the farthest object on the optical axis,
βg4 (t) is the lateral magnification of the fourth lens group at the telephoto end when focusing on the farthest object on the optical axis,
It is. The imaging apparatus according to claim 1, wherein the fourth lens group satisfies the following condition.
-0.35 <Dg4 / fg4 <-0.0005 (3)
However,
Dg4 is the thickness on the optical axis from the object side surface to the image side surface of the fourth lens group. The imaging apparatus according to claim 1, wherein the zoom lens satisfies the following condition.
0.5 <enp (w) / fw <1.8 (4)
However,
enp (w) is the distance on the optical axis from the object side refractive surface of the first lens unit to the entrance pupil at the wide angle end,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is. The imaging apparatus according to claim 1, wherein the first lens group and the fourth lens group satisfy the following conditions.
0.001 <fg4 / fg1 <30.0 (5)
However,
fg1 is a focal length of the first lens group. The first lens group includes a reflecting prism having the reflecting surface, an object-side refracting surface, and an image-side refracting surface, and the total number of reflecting surfaces that reflect the optical axis in the zoom lens is one. The imaging device according to claim 1 or 2. The first lens group includes a reflecting prism having the reflecting surface, an object-side refracting surface, and an image-side refracting surface;
The imaging apparatus according to claim 1, wherein the reflecting prism satisfies the following condition.
0.5 <Dpr / fw <2.0 (6)
However,
Dpr is the optical path length along the optical axis from the object side refractive surface to the image side refractive surface of the reflecting prism,
fw is the focal length of the entire zoom lens system at the wide-angle end,
It is. The first lens group includes a reflecting prism having the reflecting surface, an object-side refracting surface, and an image-side refracting surface;
The imaging apparatus according to claim 1, wherein the reflecting prism satisfies the following condition.
1.70 <nd (pr) <2.3 (10)
However,
nd (pr) is the d-line refractive index of the reflecting prism in the first lens group. When zooming from the wide-angle end to the telephoto end,
The first lens group is fixed;
The second lens group moves;
The imaging apparatus according to claim 1, wherein the third lens group moves so as to be positioned closer to the object side at the telephoto end than at the wide-angle end. 11. The imaging apparatus according to claim 10, wherein, when zooming from the wide-angle end to the telephoto end, the second lens group first reverses the moving direction to the object side after moving to the image side. The imaging apparatus according to claim 1, wherein the fourth lens group moves to the image side during a focusing operation from a long-distance object to a short-distance object. The second lens group is a negative lens in order from the object side, consists of two positive lens, an imaging apparatus according to claim 1 or 2, characterized in that the negative lens and the positive lens are bonded to each other . The imaging apparatus according to claim 1 or 2, wherein the fourth lens group is characterized in that it consists of two or less lenses. The imaging apparatus according to claim 1, wherein the zoom lens satisfies the following conditional expression.
1.8 <ft / fw <6.5 (9)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
ft is the focal length of the entire zoom lens system at the telephoto end,
It is. The imaging apparatus according to claim 1, further comprising an image conversion unit that converts an electrical signal including distortion by the zoom lens into an image signal in which distortion is corrected by image processing. The imaging apparatus according to claim 1, further comprising: an image conversion unit that converts an electrical signal including lateral chromatic aberration caused by the zoom lens into an image signal corrected for lateral chromatic aberration by image processing.

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