JP2010134373A - Image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup apparatus including a zoom lens which is advantageous in increasing angle of view and zoom ratio, while reducing the size. <P>SOLUTION: The image pickup apparatus includes the zoom lens, and an image pickup element arranged on an image side of the zoom lens, having an image pickup surface and converting an image formed on the image pickup surface by the zoom lens into an electric signal. The zoom lens includes, in order from its object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, and further includes an aperture stop that moves integrally with the second lens group during zooming from a wide angle end to a telephoto end. During zooming, the first lens group and the second lens group move, and a distance between the lens groups changes. The first lens group comprises, in order from the object side, two lenses, a negative lens and a positive lens. The second lens group is composed of four lenses including a positive lens and a negative lens, and satisfies a predetermined conditional expression. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus such as a video camera or a digital camera provided with a zoom lens.

  In recent years, an image pickup apparatus using a CCD or C-MOS sensor instead of a film type camera has become mainstream. An imaging apparatus such as a digital camera or a video camera can be easily miniaturized due to a small imaging surface.

  In the field of digital cameras and video cameras using small image sensors, there is a demand for imaging devices that have a small depth in the depth direction and have a high zoom ratio and a wide angle of view. For example, zoom lenses described in Patent Document 1 to Patent Document 9 are known as zoom lenses intended for use in small-sized imaging devices.

JP 2003-241091 A JP 11-52246 A JP 2006-194975 A JP 2008-46529 A JP 2007-17915 A JP 2007-140359 A JP 2007-272216 A JP 2003-113869 A JP 2006-227197 A

  However, a positive leading type zoom lens in which a lens unit having a positive refractive power closest to the object side as disclosed in Patent Document 1 is disadvantageous for thinning in a retracted state.

  Since the negative leading type zoom lens having the negative lens group closest to the object side as disclosed in Patent Document 2 can reduce the number of lens groups, it is smaller than the positive leading type zoom lens. This is advantageous from the viewpoint of conversion. However, the zoom lens disclosed in Patent Document 2 has a small zoom ratio of about 3 times. In addition, the number of lens components in the zoom lens is large, which is disadvantageous for thinning when retracted.

  The zoom lens disclosed in Patent Document 3 is excellent in that it has negative optical performance and good optical performance. However, the zoom ratio is as small as about 3 times. In addition, since the second lens group, which is a variator, is composed of three lenses, if an attempt is made to further increase the zoom ratio, the refractive power of each lens in the second lens group becomes too large, and aberrations are increased. Is likely to occur.

  In the zoom lenses disclosed in Patent Documents 4 and 5, the shape of the negative lens closest to the object is a meniscus shape having strong negative refractive power on the image side. Therefore, if an attempt is made to increase the negative refractive power of the first lens group in order to increase the zoom ratio and the angle of view beyond this, the curvature of the image side surface of the negative lens becomes too large, and aberration correction is performed. Becomes difficult.

  In the zoom lenses disclosed in Patent Literature 6, Patent Literature 7, Patent Literature 8, and Patent Literature 9, the most negative lens on the object side is a biconcave shape, and the second lens group is composed of four lenses. Yes. Thereby, the refractive power of each lens group can be shared by each lens surface, which is excellent in terms of aberration correction. However, in Patent Documents 6, 7, and 8, the zoom ratio and the angle of view at the wide-angle end are small, and in Patent Document 9, the angle of view at the wide-angle end is small and the total length is large.

  The present invention has been made in view of the above, and an object of the present invention is to provide an imaging device including a zoom lens that is advantageous in widening the angle of view and increasing the zoom ratio while realizing downsizing. To do.

In order to solve the above-described problems and achieve the object, an imaging apparatus according to a first aspect of the present invention includes a zoom lens and an image plane that is disposed on the image side of the zoom lens and has an imaging plane. The zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens element. And an aperture stop that moves together with the second lens unit during zooming from the wide-angle end to the telephoto end. During the zooming, the first lens unit and the first lens unit The two lens groups move, and the distance between each lens group changes. The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side, and the second lens group is a positive lens. Consists of four lenses including a negative lens, the following conditional expression (1), 2) is characterized by satisfying the (3).
−1.0 <(r _1a + r _1b ) / (r _1a −r _1b ) <0.98 (1)
0.30 <σ _2G /ih(max)<2.80 (2)
1.5 <Δ _2G / f ₂ <5 (3)
However,
r _1a and r _1b are paraxial radii of curvature of the object side surface and the image side surface of the negative lens in the first lens group,
σ _2G is the thickness of the second lens group on the optical axis,
ih (max) is the maximum value of the maximum image height in the effective imaging area on the imaging surface,
Δ _2G is the difference in the position of the second lens group at the telephoto end with respect to the wide-angle end,
Move to the object side as a positive sign,
f ₂ is the focal length of the second lens group,
It is.

  Disposing a lens unit having a negative refractive power in the first lens unit is advantageous in reducing the number of lens units. Reducing the number of lens groups also reduces the total number of lenses, which is advantageous for cost reduction and size reduction.

  The second lens group mainly serves as a variator and moves from the wide-angle end to the telephoto end for zooming. At this time, the first lens group is also moved, which is advantageous for adjusting the image plane position.

  By disposing the third lens group, it is possible to reduce the difference in exit angle between the wide-angle end and the telephoto end, and to correct field curvature.

  The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side, so that the principal point of the first lens group is closer to the object side and the radial size of the first lens group and the overall zoom lens length are reduced. It becomes easy to do. In addition, the chromatic aberration of the first lens group can be easily suppressed with a small number of lenses. In addition, it is advantageous for reducing the occurrence of axial aberration at the telephoto end.

  The second lens group is made up of four lenses including a positive lens and a negative lens, which makes it easy to ensure the positive refractive power of the second lens and correct aberrations, widening the angle of view and increasing the zoom ratio. Is advantageous.

  Conditional expression (1) specifies a preferable shape of the negative lens in the first lens group. Satisfying this conditional expression is advantageous for reducing curvature of field at the wide-angle end and spherical aberration at the telephoto end.

  If the upper limit of conditional expression (1) is exceeded or less than the lower limit, the paraxial curvature of the refractive surface of either the object side surface or the image side surface becomes too large. For this reason, field curvature at the wide-angle end and spherical aberration at the telephoto end are likely to occur, which is disadvantageous for achieving a high zoom ratio.

Conditional expression (2) specifies a preferable thickness on the optical axis of the second lens group with respect to the maximum image height ih (max).
In order to achieve a wide angle of view or a high zoom ratio with a negative leading type zoom lens, it is necessary to sufficiently secure the positive refractive power of the second lens group as a variator. However, when five or more conventional lenses are used, the thickness of the second lens group on the optical axis is increased, which is disadvantageous in reducing the thickness when retracted. On the contrary, if the second lens group has a configuration of three or less lenses, aberrations associated with securing positive refractive power are likely to occur, and it becomes difficult to correct axial aberrations at the telephoto end.

  By satisfying conditional expression (2), even if the second lens group is composed of four lenses, the second lens group is sufficiently compact to achieve a wide angle of view and a high zoom ratio. Can be secured. For this reason, it leads to a reduction in the overall length and a reduction in thickness when retracted.

  If the upper limit of conditional expression (2) is exceeded, the moving space for zooming becomes small, so that the positive refractive power of the second lens group becomes too large, and aberration correction becomes difficult. In addition, the thickness increases when retracted.

  If the lower limit of conditional expression (2) is not reached, sufficient positive refractive power of the second lens group will be secured and aberration correction will be difficult.

  Note that ih (max) is the maximum value of the maximum image height in the effective imaging area on the imaging surface. A technique for performing trimming imaging by changing the effective imaging area, a technique for changing the aspect ratio, and a technique for changing the effective imaging area on the wide-angle side into a barrel shape and changing it to a rectangular image signal by signal processing are known.

  When these maximum image heights change, they are set to values when the maximum image height is maximized in the effective imaging region that the imaging apparatus can take.

  Conditional expression (3) specifies preferable conditions for the amount of displacement and the focal length of the second lens unit during zooming from the wide-angle end to the telephoto end. Satisfying this conditional expression is advantageous for achieving a high zoom ratio while suppressing aberration fluctuations during zooming.

  If the lower limit of conditional expression (3) is not reached, the zooming burden of the second lens group becomes small, a large zooming burden is required after the third lens group, and the field curvature and the fluctuation of the exit pupil position become large. Come.

  If the upper limit of conditional expression (3) is exceeded, the refractive power and movement amount of the second lens group will become too large, and axial aberrations at the telephoto end and aberration fluctuations at the wide-angle end and the telephoto end will tend to increase.

  In the case where the zoom lens has a focusing mechanism, the zoom lens has a configuration in which the lens is focused on the farthest distance. Similarly, in the following configurations, when the zoom lens has a focusing mechanism, it is configured in a state in which it is focused on the farthest distance.

  In the above-described invention, it is more preferable to satisfy one or more items of the configuration described below.

In the imaging device according to the present invention, it is preferable that the most object side lens in the second lens group is a positive lens, and satisfies the following conditional expression (4).
1.1 <f ₂ / r _3a <3.0 (4)
Here, r _3a is the paraxial radius of curvature of the most object-side refractive surface in the second lens group.

  Conditional expression (4) specifies a preferable relationship between the paraxial radius of curvature of the most object-side refractive surface in the second lens group and the focal length of the second lens group. By satisfying this conditional expression, the paraxial radius of curvature becomes appropriate with respect to the focal length of the second lens group, and the zoom lens can be reduced in size, on-axis, and off-axis by positioning the principal point to the object side. This is advantageous in reducing the aberration of the lens. In addition, it is advantageous for downsizing the second lens group in the radial direction.

  By making sure that the lower limit of conditional expression (4) is not exceeded, the curvature of the object-side refractive surface is ensured, which is advantageous for downsizing in the radial direction. In addition, the curvature of other lens surfaces can be reduced, which is advantageous in reducing various aberrations.

  By making sure that the upper limit of conditional expression (4) is not exceeded, it is possible to suppress the difference in incident angles of the on-axis light beam and off-axis light beam by suppressing the excess of the refractive power of this refracting surface. This is advantageous for reducing aberrations.

  In the imaging apparatus according to the present invention, it is preferable that the zoom lens is a three-group zoom lens, and the third lens group has a positive refractive power.

  Since the third lens group has a positive refractive power, the exit pupil can be moved away from the imaging surface, the amount of peripheral light is difficult to be obtained, and the image quality at the periphery is ensured.

  In the imaging device according to the present invention, it is preferable that at least two adjacent lenses in the second lens group are cemented.

  Arranging the cemented lens in the second lens group is advantageous in correcting axial and off-axis chromatic aberration.

In the imaging device according to the present invention, it is preferable that the most object side lens in the second lens group satisfies the following conditional expression (5).
1.1 <f ₂ / L ₃ <3.0 (5)
Here, L ₃ is the focal length of the most object side lens in the second lens group.

  Conditional expression (5) specifies a preferable ratio between the focal length of the lens closest to the object side in the second lens group and the focal length of the second lens group.

  In order to achieve a reduction in thickness when retracted, a retracting method is conceivable in which the second lens group is shifted so as to move away from the optical axis of the zoom lens during photographing when retracted. When this retractable method is used, if the size of the second lens group in the radial direction can be reduced, the shift amount of the second lens group can be reduced, which is advantageous for downsizing in the radial direction.

  By satisfying conditional expression (5), the light beam can be moderately refracted by the lens closest to the object in the second lens group, which is advantageous for downsizing in the radial direction.

  By making sure that the lower limit of conditional expression (5) is not exceeded, the positive refracting power of the lens on the object side can be secured, which is advantageous for downsizing the second lens group in the radial direction. By not exceeding the upper limit of the conditional expression (5), it is possible to suppress an excessive refractive power of the lens closest to the object side in the second lens group, and it is particularly advantageous for reducing axial aberration.

  In the image pickup apparatus according to the present invention, it is preferable that the second lens group includes three positive lenses and one negative lens.

  By using three positive lenses, it is possible to share positive power well. Further, by using a negative lens, it becomes possible to improve Petzval sum and chromatic aberration.

  In the imaging apparatus according to the present invention, it is preferable that the second lens group includes a positive lens, a positive lens, a negative lens, and a positive lens in order from the object side.

  By configuring in order from the object side with a positive lens, a positive lens, a negative lens, and a positive lens, it is possible to share positive power well. Third, by using a negative lens, the principal point position can be moved to the object side, which is advantageous for securing a zoom ratio and for reducing the diameter of the second lens group.

In the imaging apparatus according to the present invention, it is preferable that the most object side lens and the most image side lens in the second lens group are positive lenses satisfying the following conditional expression (6).
_{1.7 <L 6 / L 3 <} 10 ··· (6)
However,
L ₃ is the focal length of the most object side lens in the second lens group,
L ₆ is the focal length of the most image-side lens in the second lens group,
It is.

  Conditional expression (6) specifies a preferable balance between the refractive power of the most object-side positive lens and the refractive power of the most image-side positive lens in the second lens group. Satisfying this conditional expression is advantageous in correcting axial aberrations while preventing the second lens group from being enlarged in the radial direction.

  By making sure that the lower limit of conditional expression (6) is not exceeded, the refractive power of the lens on the object side can be secured, which is advantageous for downsizing in the radial direction. By making sure that the upper limit of conditional expression (6) is not exceeded, the refractive power of the lens on the image side is secured, which is advantageous in reducing axial aberrations.

In the imaging device according to the present invention, it is preferable that the average value of the refractive indexes of all the lenses in the first lens group at the d-line satisfies the following conditional expression (7).
1.87 <AVE ( _ndg1 ) <2.40 (7)
However,
AVE (n _dg1 ) is the average value of the refractive indices at the d-line of all the lenses in the first lens group,
It is.

  Conditional expression (7) specifies a preferable average value of d-line refractive indexes of all the lenses in the first lens group. Satisfying this conditional expression is advantageous in achieving both cost reduction and securing of the negative refractive power of the first lens unit.

  By making sure that the lower limit of conditional expression (7) is not exceeded, negative refractive power can be ensured even if the curvature of each lens surface in the first lens group is suppressed, and the angle of view and zoom ratio can be reduced while suppressing aberrations. It is advantageous for securing. By making the upper limit of conditional expression (7) not exceeded, it becomes easy to reduce the cost of the lens material.

In the imaging device according to the present invention, the third lens group has a positive refractive power, and the refractive power of the second lens group and the refractive power of the third lens group satisfy the following conditional expression (8): preferable.
1.0 <P ₂ / P ₃ <4.0 (8)
However,
P ₂ is the refractive power of the second lens group,
P ₃ is the refractive power of the third lens group,
It is.

  Conditional expression (8) specifies a preferable share of positive refractive power of the second lens group and the third lens group. By satisfying the conditional expression, the positive refractive power sharing between the second lens group and the third lens group becomes good, and axial aberrations in the second lens group and off-axis aberrations in the third lens group are reduced. Is advantageous.

  Furthermore, when the third lens group is a group that moves during focusing, the movement length for zooming of the second lens group and the movement space for focusing of the third lens group are ensured to shorten the overall length. It will be advantageous.

  By making sure that the lower limit of conditional expression (8) is not exceeded, the refractive power of the second lens group can be secured, the space for zooming can be reduced, and this is advantageous in reducing the overall length. Alternatively, the refractive power of the third lens group can be suppressed, and the occurrence of off-axis aberrations, particularly field curvature and lateral chromatic aberration can be easily suppressed.

By making sure that the upper limit of conditional expression (8) is not exceeded, the refractive power of the second lens group is moderately suppressed, which is advantageous in reducing various aberrations, particularly on-axis aberrations.
The value of refractive power is the reciprocal of the focal length.

In the imaging apparatus according to the present invention, it is preferable that the second lens group and the third lens group satisfy the following conditional expressions (9) and (10).
4.0 <β ₂ (t) / β ₂ (w) <10.0 (9)
0.7 <β ₃ (t) / β ₃ (w) <2.0 (10)
However,
β ₂ (w) is the lateral magnification of the second lens group at the wide-angle end,
beta ₂ (t) denotes a lateral magnification of the second lens group at the telephoto end,
β ₃ (w) is the lateral magnification of the third lens group at the wide-angle end,
β ₃ (t) is the lateral magnification of the third lens group at the telephoto end,
It is.

  Conditional expressions (9) and (10) specify preferable zooming burdens of the second lens group and the third lens group. Satisfying conditional expressions (9) and (10) is advantageous for high zooming because the zooming load can be satisfactorily performed by the second lens unit and the third lens unit.

  By making sure that the lower limit of conditional expression (9) is not exceeded, it is possible to secure the zooming burden of the second lens group and reduce the zooming burden of the other lens groups, which is advantageous in reducing aberrations.

  By reducing the zooming burden in the second lens group so as not to exceed the upper limit of conditional expression (9), it is advantageous for securing optical performance by the second lens group having a four-lens configuration.

  By making sure that the lower limit of conditional expression (10) is not exceeded, it is possible to reduce the burden of zooming on other lens units, which is advantageous in reducing aberrations.

  By reducing the zooming burden in the third lens group so as not to exceed the upper limit of conditional expression (10), the amount of movement or refractive power of the third lens group can be reduced, which is advantageous in securing optical performance.

In the imaging apparatus according to the present invention, it is preferable that the third lens group has a positive refractive power, and the optical path lengths at the wide-angle end and the telephoto end of the zoom lens satisfy the following conditional expression (11).
0.5 <D _w / D _t ≦ 1.0 (11)
However,
D _w is the optical path length from the object side surface of the zoom lens to the imaging surface at the wide angle end,
D _t is the optical path length from the object side surface of the zoom lens to the imaging surface at the telephoto end,
It is.

  Conditional expression (11) specifies the optical path length of the zoom lens, which is advantageous for securing the angle of view and the zoom ratio. Satisfying this conditional expression is advantageous in reducing the size of the first lens unit in the radial direction at the wide-angle end and securing a variable magnification space in the second lens unit.

  A function of ensuring the space between the second lens group and the third lens group at the wide-angle end and keeping the exit pupil of the third lens group away from the image plane by making sure that the lower limit of conditional expression (11) is not exceeded. It is advantageous for securing. Alternatively, when the third lens group is a group that moves during focusing, it is advantageous to secure a moving amount for focusing of the third lens group.

  By making sure that the upper limit of conditional expression (11) is not exceeded, it is advantageous for securing the movement space of the second lens group. Alternatively, by suppressing the total length of the zoom lens at the wide-angle end, it is possible to suppress the enlargement of the size of the first lens group due to the wide angle of view.

Another object of the imaging device according to the second aspect of the present invention is to provide an imaging device that gives a user a sense of familiarity.
An image pickup apparatus according to a second aspect includes a zoom lens, an image pickup element that is disposed on an image side of the zoom lens, has an image pickup surface, and converts an image formed on the image pickup surface by the zoom lens into an electric signal; An image pickup apparatus including a signal processing unit that converts an image signal into an image signal based on an electrical signal and a monitor that displays a captured image based on the image signal, a memory that includes natural person information, and a display that displays the natural person information on the monitor And a switching operation unit.

  A person who considers the purchase of an imaging device can purchase it at a consumer electronics mass retailer with a sense of security and familiarity. In addition, attachment to the purchased image pickup device is easy to understand.

  Furthermore, a zooming operation unit that performs zooming operation of the zoom lens may be provided, and the zooming operation unit may also serve as at least a part of the display switching operation unit. The operation part can also be used, and the number of parts can be reduced.

  The natural person information may include a natural person movie image and a voice. For example, it is possible to provide the purchase requester with the features of the imaging device and the operation explanation by using the movie image and voice information. Natural person information may be one or a plurality of pieces of information of the person in charge of assembly, the designer, the store clerk, and the product planner who manufactured the imaging device.

It is another object of the present invention to provide an imaging apparatus including a zoom lens that is easy to increase the angle of view and the zoom ratio.
An imaging apparatus according to a third aspect of the present invention is an imaging device that is disposed on the image side of a zoom lens and the zoom lens, and has an imaging surface and converts an image formed on the imaging surface by the zoom lens into an electrical signal. The zoom lens includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group, and further from the wide-angle end. During zooming to the telephoto end, it has an aperture stop that moves together with the second lens group. During the zooming, the first lens group and the second lens group move, and each lens group The first lens group has a negative lens that satisfies the following conditional expression (1), and the second lens group is composed of four lenses including a positive lens and a negative lens. It is characterized by satisfying conditional expression (12).
−1.0 <(r _1a + r _1b ) / (r _1a −r _1b ) <0.98 (1)
_{1.75 <AVE (n d) <} 2.40 ··· (12)
However,
r _1a and r _1b are paraxial radii of curvature of the object side surface and the image side surface of the negative lens in the first lens group,
AVE (n _d ) is an average value of refractive indexes of all the lenses in the zoom lens from the first lens group to the third lens group,
It is.

  In the imaging device of the third aspect, conditional expression (12) may be satisfied instead of conditional expressions (2) and (3) of the present invention of the first aspect described above.

  By making sure that the lower limit of conditional expression (12) is not exceeded, the absolute value of the paraxial curvature of the various lenses in the zoom lens can be reduced even if the refractive power of each lens group is sufficiently secured. And optical performance are improved, which is advantageous for securing a zoom ratio and a field angle.

  By making the upper limit of conditional expression (12) not exceeded, it becomes easy to suppress the material cost of the lenses.

  In the imaging apparatus according to the present invention, it is preferable that the first lens group includes two lenses of a negative lens and a positive lens in order from the object side.

  The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side, so that the principal point of the first lens group is closer to the object side and the radial size of the first lens group and the overall zoom lens length are reduced. It becomes easy to do.

  In addition, the chromatic aberration of the first lens group can be easily suppressed with a small number of lenses. In addition, it is advantageous for reducing the occurrence of axial aberration at the telephoto end.

In the imaging device according to the present invention, it is preferable that the zoom lens satisfies the following conditional expression (13).
3.6 < _ft / _fw <10 (13)
However,
f _w is the focal length of the zoom lens at the wide-angle end,
f _t is the focal length of the zoom lens at the telephoto end,
It is.

  Conditional expression (13) is a conditional expression regarding a preferable zoom ratio of the zoom lens.

  It is preferable that the zoom ratio is ensured so as not to fall below the lower limit of the conditional expression (13) because the function of the present invention can be exhibited.

  By avoiding exceeding the upper limit of conditional expression (13), it becomes easy to reduce the size and cost. Moreover, it becomes easy to make optical performance favorable.

  The image pickup apparatus according to the present invention preferably 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.

  It is possible to record and display images after electrically correcting the distortion of the zoom lens. Therefore, by allowing distortion aberration of the zoom lens to occur, it becomes advantageous for correction of field curvature and coma, and as a result, it becomes easy to obtain good image quality with a small zoom lens.

  The imaging apparatus according to the present invention preferably includes an image conversion unit that converts an electrical signal including chromatic aberration of magnification due to the zoom lens into an image signal in which the chromatic aberration of magnification is corrected by image processing.

  It is preferable to have an image conversion unit that converts an electrical signal of an image captured by the zoom lens into an image signal in which color shift due to magnification chromatic aberration is corrected by image processing. By electrically correcting the chromatic aberration of magnification of the zoom lens, a better image can be obtained.

  By allowing the chromatic aberration of magnification of the zoom lens, the degree of freedom in selecting the lens material can be secured, which is advantageous for cost reduction, thinning, and high performance.

More preferably, the imaging apparatus of the present invention satisfies a plurality of the above requirements at the same time.
Further, it is preferable to limit the lower limit value, the upper limit value, or both of the conditional expressions as follows, because the effects can be easily obtained.

  For conditional expression (1), it is more preferable to set the lower limit to −1.0, more preferably 0.5. The upper limit value is more preferably 0.90, and even more preferably 0.85.

  For conditional expression (2), it is more preferable to set the lower limit to 1.00, more preferably 1.40. The upper limit value is more preferably 1.80, more preferably 1.68.

  For conditional expression (3), it is more preferable to set the lower limit value to 1.6, more preferably 1.8. The upper limit is more preferably 3.5, and even more preferably 2.1.

  For conditional expression (4), it is more preferable to set the lower limit to 1.3, more preferably 1.7. The upper limit value is more preferably 2.5, and even more preferably 2.0.

  For conditional expression (5), it is more preferable to set the lower limit value to 1.2, further 1.4. The upper limit value is more preferably 2.0, and more preferably 1.7.

  For conditional expression (6), it is more preferable to set the lower limit value to 2.0, more preferably 2.3. The upper limit value is more preferably 8.0, and even more preferably 6.5.

  For conditional expression (7), it is more preferable to set the lower limit to 1.90, more preferably 1.92. The upper limit value is more preferably 2.20, more preferably 2.10.

  For conditional expression (8), it is more preferable to let the lower limit value to be 1.2, further 1.3. The upper limit is more preferably 3.0, and more preferably 2.3.

  For conditional expression (9), it is more preferable to set the lower limit to 4.4, more preferably 4.7. The upper limit is more preferably 7.0, and even more preferably 5.3.

  For conditional expression (10), it is more preferable to set the lower limit value to 0.8, more preferably 0.9. The upper limit value is more preferably 1.5, and further preferably 1.2.

  For conditional expression (11), it is more preferable to set the lower limit value to 0.7, and further to 0.8. The upper limit is more preferably 0.99, and even more preferably 0.98.

  For conditional expression (12), it is more preferable to set the lower limit value to 1.76, more preferably 1.78. The upper limit value is more preferably 2.3, and further preferably 2.2.

  For conditional expression (13), it is more preferable to set the lower limit value to 3.8, more preferably 4.4. The upper limit value is more preferably 8.0, and even more preferably 6.5.

  The image pickup apparatus according to the present invention has an effect that it can be provided with a zoom lens that is advantageous in widening the angle of view and increasing the zoom ratio while realizing downsizing.

  Embodiments of 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 10 of the zoom lens according to the present invention will be described below. FIGS. 1 to 10 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 10, respectively. 1 to 10, the first lens group is G1, the second lens group is G2, the third lens group is G3, the brightness (aperture) stop is S, and a wavelength range limiting coat that limits infrared light is applied. The parallel flat plate constituting the 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 wavelength range limitation 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 second lens group G2. 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 all the embodiments, focusing is performed by moving the third lens group G3. 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 brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces include both surfaces of the biconcave negative lens and both surfaces of the biconvex positive lens of the first lens group G1, both surfaces of the object side biconvex positive lens of the second lens group G2, and the positive meniscus of the third lens group G3. 7 on the image side of the lens.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, a brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side after moving to the object side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces are the double-sided negative lens and the positive meniscus side of the first lens group G1, the object-side biconvex positive lens side of the second lens group G2, and the biconvex positive side of the third lens group G3. 7 on the image side of the lens.

  As shown in FIG. 3, the zoom lens of Embodiment 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, a brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side after moving to the object side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces are the double-sided negative lens and the positive meniscus side of the first lens group G1, the object-side biconvex positive lens side of the second lens group G2, and the biconvex positive side of the third lens group G3. 7 on the image side of the lens.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a negative refractive power, a brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces are the double-sided negative lens and the positive meniscus side of the first lens group G1, the object-side biconvex positive lens side of the second lens group G2, and the biconvex positive side of the third lens group G3. 7 on the image side of the lens.

  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 brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side after moving to the object side. The aperture stop S moves together with the second lens group G2.

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

  The aspheric surfaces are provided on the five surfaces of the biconcave negative lens of the first lens group G1, the both surfaces of the biconvex positive lens on the object side of the second lens group G2, and the object side surface of the positive meniscus lens. ing.

  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 brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the object side after moving to the image side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces are the double-sided negative lens of the first lens group G1, the double-sided positive lens and the double side of the positive meniscus lens on the object side of the second lens group G2, and the double-convex positive side of the third lens group G3. 7 on the image side of the lens.

  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 brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces include both surfaces of the biconcave negative lens of the first lens group G1, both surfaces of the object side biconvex positive lens of the second lens group G2, and the image side surface of the positive meniscus lens of the third lens group G3. Are provided on five surfaces.

  As shown in FIG. 8, the zoom lens of Embodiment 8 includes, in order from the object side, a first lens group G1 having a negative refractive power, a brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces include both surfaces of the biconcave negative lens of the first lens group G1, both surfaces of the object side biconvex positive lens of the second lens group G2, and the image side surface of the positive meniscus lens of the third lens group G3. Are provided on five surfaces.

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

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side after moving to the object side. The fourth lens group G4 is fixed. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surfaces are the double-sided negative lens and the positive meniscus side of the first lens group G1, the object-side biconvex positive lens side of the second lens group G2, and the biconvex positive side of the third lens group G3. 7 on the image side of the lens.

  As shown in FIG. 10, the zoom lens of Example 10 includes, in order from the object side, a first lens group G1 having a negative refractive power, a brightness (aperture) stop S, and a second lens group having a positive refractive power. G2 and a third lens group G3 having a negative refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side after moving to the object side. The aperture stop S moves together with the second lens group G2.

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

  The aspherical surface includes both surfaces of a biconcave negative lens and both surfaces of a positive meniscus lens in the first lens group G1, both surfaces of a biconvex positive lens on the object side of the second lens group G2, and both surfaces of a biconvex positive lens on the image side. , And 10 surfaces of the negative meniscus lens of the third lens group G3.

Below, the numerical data of each said Example are shown. In addition to the above, R is the radius of curvature of each lens surface, D is the thickness or spacing of each lens, nd is the refractive index of each lens at the d-line, ν _d is the Abbe number of each lens at the d-line, and K is Each cone coefficient is shown.

Each aspheric shape is expressed by the following formula (I) using each aspheric coefficient in each embodiment.
However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + K) · (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 ··· (I)
However,
r is the paraxial radius of curvature,
K is the cone coefficient,
A4, A6, A8, A10 and A12 are the fourth, sixth, eighth, tenth and twelfth aspherical 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
Object ∞ ∞
1 * -33.000 0.70 1.88300 40.76
2 * 7.781 2.50
3 * 27.495 1.90 2.10220 16.80
4 * -416.858 variable
5 Aperture 0.30
6 * 5.479 1.80 1.61881 63.85
7 * -28.056 0.30
8 7.138 1.75 1.57099 50.80
9 -23.817 0.60 1.90366 31.32
10 4.123 0.80
11 9.992 1.10 1.53100 55.60
12 54.381 Variable
13 -15.353 1.30 1.88300 40.76
14 * -7.372 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 9.99446e-05, A6 = -9.63628e-07, A8 = 2.04237e-10
Second side
k = -3.135
A4 = 6.09572e-05, A6 = 8.29447e-06, A8 = -1.60404e-07, A10 = 7.16869e-10
Third side
k = 0.000
A4 = -6.39964e-04, A6 = 8.67632e-06, A8 = -6.03020e-08
4th page
k = 0.000
A4 = -4.71619e-04, A6 = 5.19991e-06, A8 = -4.06136e-08
6th page
k = 0.084
A4 = -6.35142e-04, A6 = 6.90448e-05, A8 = -1.20381e-05, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 1.97786e-04, A6 = 7.07487e-05, A8 = -1.13387e-05, A10 = 8.32015e-07
14th page
k = 0.000
A4 = 1.15151e-03, A6 = -1.30691e-05, A8 = 2.68138e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 3.74 9.80 21.56
FNO. 2.88 4.66 6.00
Angle of view 2ω 105.03 39.26 18.08

D4 21.65 6.69 1.50
D12 2.06 10.21 24.30
D14 3.68 3.19 2.59

fb (in air) 4.97 4.47 3.88
Total length (in air) 41.73 34.42 42.73

Group focal length
f1 = -12.06 f2 = 10.93 f3 = 14.92

Numerical example 2
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -29.340 0.70 1.85135 40.10
2 * 6.777 1.52
3 * 10.860 2.00 2.00170 20.60
4 * 30.132 variable
5 Aperture 0.30
6 * 5.337 2.00 1.69839 56.54
7 * -16.575 0.10
8 12.761 1.75 1.83481 42.71
9 -9.077 0.60 1.90366 31.32
10 3.726 0.60
11 6.026 1.10 1.49700 81.54
12 10.694 Variable
13 604.034 1.60 1.85 135 40.10
14 * -15.867 Variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 4.68880e-04, A6 = -8.84965e-06, A8 = 6.14251e-08
Second side
k = -3.135
A4 = 1.34192e-03, A6 = 1.05982e-06, A8 = -5.74933e-07, A10 = 8.39406e-09
Third side
k = 0.000
A4 = -1.19540e-04
4th page
k = 0.000
A4 = -1.19553e-04, A6 = -1.03634e-06, A8 = -2.38329e-08
6th page
k = -0.438
A4 = -3.79081e-04, A6 = 3.77178e-05, A8 = -6.63306e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 5.13385e-04, A6 = 2.51731e-05, A8 = -5.09002e-06, A10 = 8.53420e-07
14th page
k = 0.000
A4 = 1.92331e-04, A6 = -4.48192e-06, A8 = 4.05357e-08

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.53 9.80 21.74
FNO. 3.50 5.11 6.00
Angle of view 2ω 98.06 43.38 19.91

D4 16.55 6.10 1.50
D12 2.00 7.26 20.18
D14 3.11 3.42 2.99

fb (in air) 4.40 4.70 4.27
Total length (in air) 35.23 30.34 38.23

Group focal length
f1 = -11.94 f2 = 9.54 f3 = 18.18

Numerical Example 3
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -35.000 0.70 1.85135 40.10
2 * 6.838 1.80
3 * 10.926 2.00 2.00170 20.60
4 * 28.379 variable
5 Aperture 0.30
6 * 5.320 1.53 1.70656 52.36
7 * -30.201 0.10
8 10.800 1.75 1.77250 49.60
9 -13.682 0.60 1.90366 31.32
10 3.889 0.60
11 9.527 1.10 1.49700 81.54
12 57.115 Variable
13 73.671 1.40 1.85135 40.10
14 * -23.751 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 4.01305e-04, A6 = -5.00245e-06, A8 = 2.08702e-08
Second side
k = -3.135
A4 = 6.81679e-04, A6 = 1.92654e-05, A8 = -4.90041e-07, A10 = 2.88794e-09
Third side
k = 0.000
A4 = -5.84207e-04, A6 = 2.05468e-05, A8 = -2.38179e-07
4th page
k = 0.000
A4 = -3.27069e-04, A6 = 1.33908e-05, A8 = -2.09187e-07
6th page
k = -0.160
A4 = -5.55522e-04, A6 = 3.64091e-05, A8 = -8.52940e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 1.67778e-04, A6 = 3.09282e-05, A8 = -6.80590e-06, A10 = 7.52751e-07
14th page
k = 0.000
A4 = 3.64817e-04, A6 = -1.11486e-05, A8 = 1.98493e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.49 9.80 21.56
FNO. 3.50 5.03 6.00
Angle of view 2ω 91.57 42.35 19.50

D4 18.90 6.72 1.50
D12 2.56 8.06 20.97
D14 3.49 3.63 2.59

fb (in air) 4.78 4.92 3.87
Total length (in air) 38.12 31.58 38.23

Group focal length
f1 = -12.66 f2 = 10.32 f3 = 11.24

Numerical Example 4
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -38.664 0.70 1.85135 40.10
2 * 6.310 1.80
3 * 8.901 2.00 2.00170 20.60
4 * 16.647 Variable
5 Aperture 0.30
6 * 5.217 2.00 1.76802 49.24
7 * -16.728 0.10
8 13.257 1.75 1.75500 52.32
9 -6.940 0.60 1.90366 31.32
10 3.652 0.60
11 7.522 1.10 1.49700 81.54
12 17.611 Variable
13 73.671 1.60 1.85135 40.10
14 * -17.850 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 7.72121e-04, A6 = -1.32903e-05, A8 = 8.19472e-08
Second side
k = -3.135
A4 = 1.31070e-03, A6 = 2.72921e-05, A8 = -5.31690e-07, A10 = -6.96475e-10
Third side
k = 0.000
A4 = -7.72827e-04, A6 = 1.65807e-05, A8 = -7.50695e-08
4th page
k = 0.000
A4 = -5.00670e-04, A6 = 7.07748e-06, A8 = -5.62963e-08
6th page
k = -0.145
A4 = -6.47506e-04, A6 = 3.59886e-05, A8 = -7.47112e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 4.73085e-04, A6 = 2.94405e-05, A8 = -5.48603e-06, A10 = 8.25074e-07
14th page
k = 0.000
A4 = 2.95904e-04, A6 = -9.31694e-06, A8 = 1.43807e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.49 9.80 21.56
FNO. 3.50 5.33 6.00
Angle of view 2ω 91.08 42.49 19.78

D4 13.98 5.39 1.50
D12 1.31 7.33 20.31
D14 3.13 3.04 2.58

fb (in air) 4.42 4.33 3.87
Total length (in air) 32.27 29.59 38.23

Group focal length
f1 = -10.97 f2 = 8.93 f3 = 17.01

Numerical Example 5
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -33.169 0.70 1.85135 40.10
2 * 6.380 1.80
3 11.481 1.90 2.00170 20.60
4 36.652 Variable
5 Aperture 0.30
6 * 5.519 2.00 1.76802 49.24
7 * -387.323 0.10
8 6.944 1.75 1.65838 59.27
9 -8.000 0.60 1.90366 31.32
10 3.722 0.60
11 * 6.018 1.10 1.54975 48.94
12 15.865 Variable
13 50.000 1.80 1.85135 40.10
14 -30.573 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 4.65723e-04, A6 = -6.75729e-06, A8 = 3.00586e-08
Second side
k = -3.135
A4 = 1.50232e-03, A6 = -4.04704e-06, A8 = -3.75924e-07, A10 = 2.65200e-09
6th page
k = -0.152
A4 = -2.70882e-04, A6 = 3.16426e-05, A8 = -5.34649e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = -2.97122e-04, A6 = 4.73560e-05, A8 = -4.89964e-06, A10 = 1.14175e-06
11th page
k = 0.000
A4 = -1.68514e-03, A6 = 3.50142e-05, A8 = 5.59533e-06

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.49 9.90 21.56
FNO. 3.50 4.97 6.00
Angle of view 2ω 93.93 43.43 20.25

D4 18.08 5.87 1.50
D12 2.43 6.31 19.81
D14 2.78 4.30 2.98

fb (in air) 4.07 5.59 4.27
Total length (in air) 37.23 30.42 38.23

Each group focal length
f1 = -11.93 f2 = 9.78 f3 = 22.52

Numerical Example 6
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -51.865 0.70 1.85135 40.10
2 * 6.577 1.80
3 9.480 2.00 2.00170 20.60
4 18.105 Variable
5 Aperture 0.30
6 * 5.349 2.00 1.76802 49.24
7 * -42.129 0.10
8 10.657 1.75 1.77250 49.60
9 -5.835 0.60 1.90366 31.32
10 4.269 0.60
11 * 6.623 1.10 1.49700 81.54
12 * 9.614 Variable
13 73.671 1.40 1.85135 40.10
14 * -15.796 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 3.67543e-04, A6 = -3.19659e-06, A8 = 5.23731e-09
Second side
k = -3.135
A4 = 1.59061e-03, A6 = -1.99516e-05, A8 = 8.78972e-07, A10 = -1.57760e-08
6th page
k = -0.009
A4 = -3.60051e-04, A6 = 2.49613e-05, A8 = -6.08935e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 1.86120e-04, A6 = 2.61785e-05, A8 = -4.67752e-06, A10 = 1.01515e-06
11th page
k = 0.000
A4 = -1.32642e-03, A6 = -1.45230e-04
12th page
k = 0.000
A4 = 6.47255e-04, A6 = 6.74404e-06
14th page
k = 0.000
A4 = 2.04930e-04, A6 = -1.01224e-05, A8 = 1.83143e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.49 9.80 21.56
FNO. 3.50 5.44 6.00
Angle of view 2ω 90.46 43.49 20.48

D4 14.92 6.16 1.50
D12 1.23 8.08 20.52
D14 3.37 2.55 2.57


fb (in air) 4.66 3.84 3.86
Total length (in air) 33.16 30.43 38.23

Group focal length
f1 = -11.99 f2 = 9.40 f3 = 15.39

Numerical Example 7
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -33.000 0.70 1.88300 40.76
2 * 7.848 2.50
3 29.120 1.90 2.10220 16.80
4 -470.707 Variable
5 Aperture 0.30
6 * 5.630 1.80 1.61881 63.85
7 * -21.128 0.30
8 8.079 1.75 1.57099 50.80
9 -20.222 0.60 1.90366 31.32
10 4.574 0.80
11 11.672 1.10 1.53100 55.60
12 67.163 Variable
13 -14.250 1.90 1.88300 40.76
14 * -7.372 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 9.99446e-05, A6 = -9.63628e-07, A8 = 2.04237e-10
Second side
k = -3.135
A4 = 2.99480e-04, A6 = 1.83296e-06, A8 = -1.23683e-07, A10 = 8.63364e-10
6th page
k = 0.101
A4 = -7.08773e-04, A6 = 6.60492e-05, A8 = -1.29815e-05, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 1.81705e-04, A6 = 6.06427e-05, A8 = -1.15239e-05, A10 = 7.82583e-07
14th page
k = 0.000
A4 = 1.16896e-03, A6 = -8.05662e-06, A8 = 2.21234e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 3.74 9.80 21.56
FNO. 2.88 4.60 6.00
Angle of view 2ω 105.14 38.55 17.77

D4 21.16 6.32 1.50
D12 1.75 9.65 23.70
D14 3.88 3.60 2.59

fb (in air) 5.17 4.89 3.88
Total length (in air) 41.73 34.50 42.73

Group focal length
f1 = -11.70 f2 = 10.75 f3 = 15.32

Numerical Example 8
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -74.353 0.70 1.88300 40.76
2 * 6.930 2.50
3 14.744 1.90 2.10220 16.80
4 31.398 Variable
5 Aperture 0.30
6 * 5.727 1.80 1.61881 63.85
7 * -22.820 0.30
8 8.051 1.75 1.57099 50.80
9 -17.795 0.60 1.90366 31.32
10 4.701 0.80
11 15.493 1.10 1.53100 55.60
12 -38.885 Variable
13 -12.297 1.30 1.88300 40.76
14 * -6.969 variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 9.99446e-05, A6 = -9.63628e-07, A8 = 2.04237e-10
Second side
k = -3.135
A4 = 7.80651e-04, A6 = -6.85124e-06, A8 = 2.07357e-08, A10 = -3.80663e-10
6th page
k = 0.136
A4 = -7.37642e-04, A6 = 6.42851e-05, A8 = -1.15529e-05, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 6.91906e-05, A6 = 6.98701e-05, A8 = -1.11219e-05, A10 = 8.38141e-07
14th page
k = 0.000
A4 = 1.10831e-03, A6 = -8.00999e-06, A8 = 1.76000e-07

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 3.74 9.80 21.56
FNO. 2.88 4.54 6.00
Angle of view 2ω 102.62 39.46 18.26

D4 21.24 6.40 1.50
D12 2.49 10.25 24.29
D14 3.66 3.39 2.60

fb (in air) 4.95 4.67 3.89
Total length (in air) 41.73 34.38 42.73

Group focal length
f1 = -11.44 f2 = 10.64 f3 = 16.34

Numerical Example 9
Unit mm


Surface data surface number rd nd νd
Object ∞ ∞
1 * -32.955 0.70 1.85135 40.10
2 * 6.700 1.68
3 * 10.187 2.00 2.00170 20.60
4 * 28.354 variable
5 Aperture 0.30
6 * 5.349 2.00 1.69839 56.54
7 * -20.502 0.10
8 10.179 1.75 1.83481 42.71
9 -6.909 0.60 1.90366 31.32
10 3.436 0.60
11 4.386 1.10 1.49700 81.54
12 5.639 Variable
13 604.034 1.60 1.85 135 40.10
14 * -15.867 Variable
15 32.429 1.20 1.51633 64.14
16 -27.967 0.05
17 ∞ 0.40 1.51633 64.14
18 ∞ 0.40
19 ∞ 0.40 1.51700 64.20
20 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 5.48695e-04, A6 = -8.28778e-06, A8 = 3.64347e-08
Second side
k = -3.135
A4 = 1.05147e-03, A6 = 2.82178e-06, A8 = -3.13378e-07, A10 = 2.41864e-09
Third side
k = 0.000
A4 = -3.66588e-04
4th page
k = 0.000
A4 = -1.53752e-04, A6 = -1.82943e-06, A8 = -4.03432e-08
6th page
k = -0.268
A4 = -3.67676e-04, A6 = 3.58032e-05, A8 = -5.87865e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 5.45277e-04, A6 = 1.54624e-05, A8 = -2.83367e-06, A10 = 8.31427e-07
14th page
k = 0.000
A4 = 2.47487e-04, A6 = -4.26395e-06, A8 = 5.59056e-08

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.53 9.80 21.74
FNO. 3.50 5.09 6.00
Angle of view 2ω 91.08 42.02 19.39

D4 17.86 6.30 1.50
D12 1.59 6.48 20.27
D14 2.51 3.28 2.99

fb (in air) 1.34 1.34 1.33
Total length (in air) 36.94 31.03 39.73

Group focal length
f1 = -13.29 f2 = 10.04 f3 = 18.18 f4 = 29.28

Numerical Example 10
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -30.134 0.70 1.85135 40.10
2 * 6.700 1.52
3 * 10.000 2.00 2.00170 20.60
4 * 19.715 Variable
5 Aperture 0.30
6 * 5.585 2.00 1.69100 54.82
7 * -23.851 0.10
8 102.158 1.75 1.83481 42.71
9 26.425 0.60 1.90366 31.32
10 4.922 0.60
11 * 6.856 1.80 1.49700 81.54
12 * -16.833 variable
13 * 20.501 0.86 1.49700 81.54
14 * 19.414 Variable
15 ∞ 0.40 1.51633 64.14
16 ∞ 0.40
17 ∞ 0.40 1.51700 64.20
18 ∞ 0.36
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 7.01525e-04, A6 = -1.05131e-05, A8 = 4.56206e-08
Second side
k = -3.135
A4 = 1.40211e-03, A6 = 4.07568e-06, A8 = 5.95034e-08, A10 = -8.04560e-09
Third side
k = 0.000
A4 = -4.11128e-05
4th page
k = 0.000
A4 = 1.00636e-04, A6 = -6.39290e-06, A8 = -3.88316e-08
6th page
k = -0.503
A4 = -5.04468e-05, A6 = 3.99543e-05, A8 = -6.91907e-06, A10 = 7.54600e-07
7th page
k = 0.000
A4 = 4.43178e-04, A6 = 3.59271e-05, A8 = -7.84938e-06, A10 = 1.06221e-06
11th page
k = 0.000
A4 = -1.75199e-05, A6 = -1.50346e-05, A8 = 2.47379e-06
12th page
k = 0.000
A4 = -2.30795e-05, A6 = 4.23380e-06, A8 = 6.32128e-07
13th page
k = 0.000
A4 = 4.16931e-05, A6 = -3.12374e-06, A8 = 1.56048e-07
14th page
k = 0.000
A4 = 1.01805e-03, A6 = -2.11784e-05, A8 = 1.32318e-06

Zoom data
Wide angle Medium Telephoto height 3.84 3.84 3.84
Focal length 4.53 9.80 21.74
FNO. 3.50 4.75 6.00
Angle of view 2ω 92.07 42.39 18.98

D4 19.57 7.30 1.50
D12 3.40 7.44 21.56
D14 4.24 5.33 2.99

fb (in air) 5.52 6.62 4.28
Total length (in air) 40.73 33.60 39.58

Group focal length
f1 = -10.35 f2 = 10.06 f3 = -1000.10

Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 10 are shown in FIGS. In these aberration diagrams, (a) is the wide angle end, (b) is the intermediate focal length state, (c) is the spherical aberration (SA), astigmatism (AS), distortion (DT), and magnification at the telephoto end. Chromatic aberration (CC) is shown. In each figure, “FIY” indicates the maximum image height.

Next, the values of conditional expressions (1) to (13) in each example will be listed.

Example 1 Example 2 Example 3 Example 4 Example 5
(1) (r1a + r1b) / (r1a-r1b)
0.62 0.62 0.67 0.72 0.68
(2) Σ2G / ih 1.65 1.60 1.48 1.60 1.60
(3) Δ2G / f2 1.93 1.89 1.70 2.06 1.80
(4) f2 / r3a 1.99 1.79 1.94 1.71 1.77
(5) f2 / L3 1.45 1.59 1.58 1.66 1.38
(6) L6 / L3 3.02 4.29 3.50 4.73 2.39
(7) AVE (ndg1) 1.993 1.927 1.927 1.927 1.927
(8) P2 / P3 1.37 1.91 2.06 1.91 2.30
(9) β2 (t) / β2 (w) 5.23 4.76 4.55 4.60 4.86
(10) β3 (t) / β3 (w) 1.10 1.01 1.06 1.04 0.99
(11) Dw / Dt 0.98 0.92 1.00 0.85 0.97
(12) AVE (nd) 1.785 1.805 1.798 1.804 1.798
_{(13) f t / f w} 5.76 4.80 4.80 4.80 4.80

Example 6 Example 7 Example 8 Example 9 Example 10
(1) (r1a + r1b) / (r1a-r1b)
0.77 0.62 0.83 0.66 0.64
(2) Σ2G / ih 1.60 1.65 1.65 1.60 1.78
(3) Δ2G / f2 1.97 1.92 1.95 1.91 1.68
(4) f2 / r3a 1.76 1.91 1.86 1.88 1.80
(5) f2 / L3 1.49 1.46 1.40 1.60 1.49
(6) L6 / L3 6.06 3.58 2.77 4.90 1.49
(7) AVE (ndg1) 1.927 1.993 1.993 1.927 1.927
(8) P2 / P3 1.64 1.42 1.54 1.81 -99.41
(9) β2 (t) / β2 (w) 4.47 5.17 5.30 4.98 4.81
(10) β3 (t) / β3 (w) 1.08 1.12 1.09 0.96 1.00
(11) Dw / Dt 0.98 0.92 0.98 0.93 1.03
(12) AVE (nd) 1.807 1.785 1.785 1.769 1.754
_{(13) f t / f w} 4.80 5.76 5.76 4.80 4.80

(Anti-reflective 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, USP 7116482, and the like.

As a coating material to be used, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , CeO having a relatively high refractive index is selected according to the refractive index of the base lens and that of the adhesive. ₂ , coating material such as SnO ₂ , In ₂ O ₃ , ZnO, Y ₂ O ₃ , coating material such as MgF ₂ , SiO ₂ , Al ₂ O _{3 with} relatively low refractive index, etc. 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-coat as in 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.

(Distortion signal processing)
In the zoom lens of the above embodiment, barrel distortion occurs at the wide angle end on the rectangular photoelectric conversion surface. 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. Note that image processing is performed in which distortion is left at -3% at the wide-angle end.

  Examples 11 to 20 are examples in which the zoom lenses of Examples 1 to 10 are used, respectively, and are used in an imaging apparatus that electrically corrects distortion, and the shape of the effective imaging region changes during zooming. Therefore, it is different from the embodiment corresponding to the image height and the angle of view in the zoom state.

  In Examples 11 to 20, an image is recorded and displayed after electrically correcting barrel distortion generated on the wide angle side.

  In Examples 11 to 20, the length in the short side direction of the photoelectric conversion surface is the same as the length in the short side direction of the effective imaging region at the wide angle end, and as described above, distortion after image processing is performed. The effective imaging region is determined so that about 3% remains. Of course, an image obtained by converting a smaller barrel-shaped area into a rectangular shape as an effective imaging area may be recorded and reproduced.

The zoom lens of the eleventh embodiment is the same as the zoom lens of the first embodiment.
The zoom lens of Example 12 is the same as the zoom lens of Example 2.
The zoom lens of the thirteenth embodiment is the same as the zoom lens of the third embodiment.
The zoom lens of Example 14 is the same as the zoom lens of Example 4.
The zoom lens of Example 15 is the same as the zoom lens of Example 5.
The zoom lens of Example 16 is the same as the zoom lens of Example 6.
The zoom lens of the seventeenth embodiment is the same as the zoom lens of the seventh embodiment.
The zoom lens of Example 18 is the same as the zoom lens of Example 8.
The zoom lens of Example 19 is the same as the zoom lens of Example 9.
The zoom lens of Example 20 is the same as the zoom lens of Example 10.

Data on the image height and the total angle of view in Example 11 are shown below. Hereinafter, the values at the intermediate focal length state and the telephoto end are the same as in the corresponding Examples 1 to 10, respectively.
Various data
Wide-angle image height 3.47
Angle of view 2ω 94.85

Data of the image height and the total angle of view in Example 12 are shown below.
Wide-angle image height 3.40
Angle of view 2ω 86.83

Data of image height and full angle of view in Example 13 are shown below.
Wide-angle image height 3.56
Angle of view 2ω 85.53

Data of the image height and the total angle of view in Example 14 are shown below.
Wide-angle image height 3.57
Angle of view 2ω 85.66

Data of the image height and the total angle of view in Example 15 are shown below.
Wide-angle image height 3.52
Angle of view 2ω 86.59

Data of image height and full angle of view in Example 16 are shown below.
Wide-angle image height 3.59
Angle of view 2ω 85.9

Data of image height and full angle of view in Example 17 are shown below.
Wide-angle image height 3.48
Angle of view 2ω 94.38

Data of image height and full angle of view in Example 18 are shown below.
Wide-angle image height 3.55
Angle of view 2ω 94.90

Data of image height and full angle of view in Example 19 are shown below.
Wide-angle image height 3.57
Angle of view 2ω 84.78

Data on the image height and the total angle of view in Example 20 are shown below.
Wide-angle image height 3.54
Angle of view 2ω 85.07

(Signal processing of lateral chromatic aberration)
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 electronically correct the magnification chromatic aberration of the image, the amount of deviation of the imaging position 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, if an image composed of output signals of three primary colors of red (R), green (G), and blue (B) is described, an R and B imaging position shift with respect to G is obtained for each pixel. It is only necessary to perform coordinate conversion of the captured image so as to eliminate the deviation, and then output R and B signals.

  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 may be stored in the device. By referring to the correction data according to the zoom position, it is possible to output the second and third primary color signals in which the deviation of the second and third primary colors from 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. 21, 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. 21, 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
However,
ω is the half angle of view of the subject,
f is the focal length of the imaging optical system (in the present invention, the zoom lens),
α is 0 or more and 1 or less.

Here, if the ideal image height corresponding to the circle (image height) of 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 aberration is electrically corrected, the radius inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface on the reproduced image. The magnification on the circumference of the circle of R (image height) is fixed, and the other points on the circumference of the circle (image height) of radius r (ω) are moved in a substantially radial direction to obtain a radius r ′ ( If correction can be performed by moving the concentric circles so that ω), it is considered advantageous in terms of data amount and calculation amount.

  However, the optical image is no longer a continuous amount (due to sampling) when captured by the electronic image sensor. Therefore, strictly speaking, the circle with the radius R drawn on the optical image is not an accurate circle unless the pixels on the electronic image sensor are arranged radially.

  That is, in the shape correction of the image data represented for each discrete coordinate point, there is no circle that can fix the magnification. Therefore, it is preferable to use a method of determining the coordinates (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 or an electronic image pickup device in an electronic image pickup apparatus having a zoom lens, and the circle of the radius R drawn on the optical image is asymmetric. It is effective for correction when 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 should satisfy the following conditional expression in order to prevent the image after distortion correction from having 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.

The radius R preferably 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 reducing the size is ensured even if the angle of view is widened. it can.

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 in 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 near the telephoto end in the divided zone,
r ′ (ω) = α · f · tan ω
A correction amount when a correction result satisfying the above is obtained may be calculated, and the final correction amount may be obtained by uniformly multiplying the correction amount by a coefficient for each focal length.

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)
22 to 24 are conceptual diagrams of the configuration of the digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 141. FIG. 22 is a front perspective view showing the appearance of the digital camera 140, FIG. 23 is a rear front view thereof, and FIG. 24 is a schematic cross-sectional view showing the configuration of the digital camera 140. However, in FIGS. 22 and 24, the photographing optical system 141 is not retracted. 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 button 145, a flash 146, a liquid crystal display monitor 147, a focal length change button 161, When the photographic optical system 141 is retracted, including the setting change switch 162, the photographic optical system 141, the finder optical system 143, and the flash 146 are covered with the cover 160 by sliding the cover 160. When the cover 160 is opened and the camera 140 is set in the shooting state, the shooting optical system 141 is in the non-collapsed state of FIG. 24. When the shutter button 145 arranged on the upper part of the camera 140 is pressed, shooting is performed in conjunction therewith. Photographing is performed through the optical system 141, for example, the zoom lens of the first embodiment. An object image formed by the photographic optical system 141 is formed on the imaging surface of the CCD 149 through a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 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 finder objective optical system 153 includes a plurality of lens groups (three groups in the figure) and two prisms, and includes a zoom optical system whose focal length changes in conjunction with the zoom lens of the photographing optical system 141. The object image formed by the finder objective optical system 153 is formed on the field frame 157 of the erecting prism 155 that is an image erecting member. Behind the erecting prism 155, an eyepiece optical system 159 that guides the erect image to the observer eyeball E is disposed. A cover member 150 is disposed on the exit side of the eyepiece optical system 159.

  The digital camera 140 configured in this way has the imaging optical system 141 according to the present invention, which is extremely thin when retracted, and has high zooming performance and extremely stable imaging performance in the entire zooming range. A small size and wide angle of view can be realized.

(Internal circuit configuration)
FIG. 25 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. 25, 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 of view can be realized. In addition, fast focusing operation on the wide-angle side and the telephoto side is possible.

  As described above, the imaging apparatus according to the present invention is useful when a wide angle of view, a high zoom ratio, and a reduction in size are required.

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. FIG. 5 is a lens cross-sectional view at a wide angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to a second embodiment of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to a third embodiment of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Embodiment 4 of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 5 of the zoom lens of the present invention. FIG. 10 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 6 of the zoom lens of the present invention. FIG. 10 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 7 of the zoom lens of the present invention. FIG. 10 is a lens cross-sectional view at a wide angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to an eighth embodiment of the zoom lens of the present invention. FIG. 10 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 9 of the zoom lens of the present invention. FIG. 14 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 10 of the zoom lens of the present 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. FIG. 10 is an aberration diagram for Example 10 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 retractable 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.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group S ... Brightness (aperture) stop F ... Low pass filter C ... Cover glass I ... Image surface 112 ... Operation part 113 ... Control part 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 optics System 142 ... Optical path for photographing 143 ... Optical system for viewfinder 144 ... Optical path for viewfinder 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 160 ... cover 161 ... focal length change button 162 ... setting change switch

Claims (18)

A zoom lens,
An image sensor disposed on the image side of the zoom lens and having an imaging surface and converting an image formed on the imaging surface by the zoom lens into an electrical signal;
The zoom lens is
From the object side,
A first lens unit having negative refractive power;
A second lens group having positive refractive power;
A third lens group,
further,
When zooming from the wide-angle end to the telephoto end, it has an aperture stop that moves together with the second lens group,
During the zooming, the first lens group and the second lens group move, and the interval between the lens groups changes,
The first lens group is composed of two lenses of a negative lens and a positive lens in order from the object side,
The second lens group is composed of four lenses including a positive lens and a negative lens,
An image pickup apparatus satisfying the following conditional expressions (1), (2), and (3):
−1.0 <(r _1a + r _1b ) / (r _1a −r _1b ) <0.98 (1)
0.30 <σ _2G /ih(max)<2.80 (2)
1.5 <Δ _2G / f ₂ <5 (3)
However,
r _1a and r _1b are paraxial radii of curvature of the object side surface and the image side surface of the negative lens in the first lens group,
σ _2G is the thickness of the second lens group on the optical axis,
ih (max) is the maximum value of the maximum image height in the effective imaging area on the imaging surface,
Δ _2G is the difference in position of the second lens group at the telephoto end with respect to the wide-angle end,
Move to the object side as a positive sign,
f ₂ is the focal length of the second lens group,
It is. The imaging apparatus according to claim 1, wherein a lens closest to the object side in the second lens group is a positive lens, and satisfies the following conditional expression (4).
1.1 <f ₂ / r _3a <3.0 (4)
Here, r _3a is the paraxial radius of curvature of the most object-side refractive surface in the second lens group.   The imaging apparatus according to claim 1, wherein the zoom lens is a three-group zoom lens, and the third lens group has a positive refractive power.   The imaging apparatus according to any one of claims 1 to 3, wherein at least two adjacent lenses in the second lens group are cemented. 5. The imaging apparatus according to claim 1, wherein a lens closest to the object side in the second lens group satisfies the following conditional expression (5): 6.
1.1 <f ₂ / L ₃ <3.0 (5)
Here, L ₃ is the focal length of the most object side lens in the second lens group.   The imaging device according to any one of claims 1 to 5, wherein the second lens group includes three positive lenses and one negative lens.   The image pickup apparatus according to claim 1, wherein the second lens group includes a positive lens, a positive lens, a negative lens, and a positive lens in order from the object side. 8. The lens according to claim 1, wherein the most object-side lens and the most image-side lens in the second lens group are positive lenses that satisfy the following conditional expression (6). The imaging device described in 1.
1.7 <L ₆ / L ₃ <10 (6)
However,
L ₃ is the focal length of the most object side lens in the second lens group,
L ₆ is the focal length of the most image-side lens in the second lens group,
It is. 9. The average value of the refractive index at the d-line of all the lenses in the first lens group satisfies the following conditional expression (7): 9. Imaging device.
1.87 <AVE ( _ndg1 ) <2.40 (7)
However, AVE (n _dg1 ) is the average value of the refractive indexes at the d-line of all the lenses in the first lens group. The third lens group has a positive refractive power, and the refractive power of the second lens group and the refractive power of the third lens group satisfy the following conditional expression (8): The imaging device according to any one of claims 1 to 9.
1.0 <P ₂ / P ₃ <4.0 (8)
However,
P ₂ is the refractive power of the second lens group,
P ₃ is the refractive power of the third lens group,
It is. The imaging device according to any one of claims 1 to 10, wherein the second lens group and the third lens group satisfy the following conditional expressions (9) and (10).
4.0 <β ₂ (t) / β ₂ (w) <10.0 (9)
0.7 <β ₃ (t) / β ₃ (w) <2.0 (10)
However,
β ₂ (w) is the lateral magnification of the second lens group at the wide-angle end,
β ₂ (t) is the lateral magnification of the second lens group at the telephoto end,
β ₃ (w) is the lateral magnification of the third lens group at the wide-angle end,
β ₃ (t) is the lateral magnification of the third lens group at the telephoto end,
It is. The third lens group has a positive refractive power, and the optical path lengths at the wide-angle end and the telephoto end of the zoom lens satisfy the following conditional expression (11). The imaging device according to any one of the above.
0.5 <D _w / D _t ≦ 1.0 (11)
However,
D _w is the optical path length from the object side surface of the zoom lens to the imaging surface at the wide-angle end,
D _t is the optical path length from the object side surface of the zoom lens to the imaging surface at the telephoto end,
It is. A zoom lens,
An image sensor that is disposed on the image side of the zoom lens, has an imaging surface, and converts an image formed on the imaging surface by the zoom lens into an electrical signal;
A signal processing unit for converting into an image signal based on the electrical signal;
A monitor that displays a captured image based on the image signal;
An imaging device comprising:
Memory containing natural person information,
A display switching operation unit for displaying the natural person information on the monitor;
An imaging apparatus comprising: A zoom lens,
An image sensor that is disposed on the image side of the zoom lens, has an imaging surface, and converts an image formed on the imaging surface by the zoom lens into an electrical signal;
With
The zoom lens is
From the object side,
A first lens unit having negative refractive power;
A second lens group having positive refractive power;
A third lens group,
further,
When zooming from the wide-angle end to the telephoto end, it has an aperture stop that moves together with the second lens group,
During the zooming, the first lens group and the second lens group move, and the interval between the lens groups changes,
The first lens group has a negative lens that satisfies the following conditional expression (1):
The second lens group is composed of four lenses including a positive lens and a negative lens,
An image pickup apparatus satisfying the following conditional expression (12):
−1.0 <(r _1a + r _1b ) / (r _1a −r _1b ) <0.98 (1)
_{1.75 <AVE (n d) <} 2.40 ··· (12)
However,
r _1a and r _1b are paraxial radii of curvature of the object side surface and the image side surface of the negative lens in the first lens group,
AVE (n _d ) is an average value of refractive indexes of all the lenses from the first lens group to the third lens group in the zoom lens;
It is.   The imaging device according to claim 14, wherein the first lens group includes two lenses of the negative lens and the positive lens in order from the object side. The imaging apparatus according to claim 1, wherein the zoom lens satisfies the following conditional expression (13):
3.6 < _ft / _fw <10 (13)
However,
f _w is the focal length of the zoom lens at the wide-angle end,
f _t is the focal length of the zoom lens at the telephoto end,
It is.   The imaging according to any one of claims 1 to 16, 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. apparatus.   18. The image processing apparatus according to claim 1, further comprising: an image conversion unit that converts an electrical signal including chromatic aberration of magnification due to the zoom lens into an image signal in which the chromatic aberration of magnification is corrected by image processing. Imaging device.

Images