JP4947992B2 - Zoom lens and imaging apparatus using the same - Google Patents

Description

  The present invention relates to a zoom lens and an image pickup apparatus using the same, and more particularly to a zoom lens having a refractive power arrangement of negative, positive and positive types and an image pickup apparatus including the same.

  In recent years, digital still cameras have been downsized and imaging functions have been incorporated into mobile phones, and imaging lenses have been required to be further reduced in size and thickness.

  These photographic lenses are desired to have a zoom magnification in which the zoom ratio from the wide angle end to the telephoto end exceeds 2.5.

  In order to realize such a thin zoom lens, a method of bending the optical axis in the vertical direction using a reflecting member in the zoom lens, or a method of retracting a part of the lens group constituting the zoom lens outside the optical axis Zoom lenses are known.

  However, the method of bending using a reflecting member requires a space for bending the light beam and a space for moving the lens group for securing a zoom ratio. Therefore, these spaces are not lost when the imaging device such as a camera is not used, which is disadvantageous for reducing the volume of the imaging device when not used. Further, the layout in the imaging apparatus is limited by bending the optical axis.

  On the other hand, in the method of retracting a part of the lens group when not in use, a mechanism for retracting the lens group is added. Therefore, it is difficult to suppress the influence when the lens group is decentered with respect to the optical axis. Further, since a retracting drive means for retracting a part of the lens group is required, it is difficult to suppress the volume when not in use, which is disadvantageous in terms of cost.

In addition, as a type of power distribution of each group in a zoom lens that is reduced in size by a normal retractable method,
Negative and positive zoom lens,
Negative, positive, negative type zoom lens,
Negative, positive, positive type zoom lens,
It has been known.

  Among these, the negative and positive type zoom lenses have a small number of lens groups, and are advantageous in reducing the total thickness of the lens frame that directly holds the lenses. However, in order to reduce the overall length while ensuring a zoom ratio, it is necessary to move the first lens group back and forth during zooming so that the second lens group includes a region where the same magnification image is formed. In this case, when focusing is performed by moving the second lens group, the moving direction of the second lens group during focusing to a short distance in the magnification state before and after sandwiching the equal magnification imaging state is reversed. Further, when the second lens unit is in the same magnification state at the time of focusing on infinity, focusing to a short distance cannot be performed. Therefore, the second lens group cannot be used as the focus group.

  Accordingly, the first lens group is moved for focusing or the entire zoom lens is moved, which leads to an increase in the total length of the lens frame including the focusing mechanism. As a result, it is disadvantageous for thinning and securing a zoom ratio.

  On the other hand, the negative, positive, and negative type zoom lenses and the negative, positive, and positive type zoom lenses are advantageous in that the increase in the total length can be suppressed by performing focusing with the third lens group.

  Among these, negative, positive, and negative type zoom lenses have a negative refractive power disposed immediately before the on-axis image plane, which is disadvantageous for constructing a bright zoom lens with a small F number. In addition, the incident angle of the most off-axis light beam on the image plane is likely to be large, and is susceptible to shading when using a CCD. In addition, aberrations are magnified by the negative lens group, which is easily affected by variations in production, and it is difficult to ensure stable quality.

  On the other hand, since the negative, positive, and positive type zoom lenses do not have the above-described drawbacks, it is easy to ensure optical performance, and if the focusing is performed by moving the third lens group, a change in the total length due to focusing can be suppressed.

  Among negative, positive, and positive type zoom lenses, a type in which the third lens unit moves toward the image side at the telephoto end with respect to the wide-angle end or hardly moves is generally known. However, in such a moving system, the position of the third lens group at the telephoto end is close to the image plane, so that the off-axis light beam in the third lens group increases and the lens diameter tends to increase. Further, when the third lens group is moved to the focusing operation, when the third lens group is close to the image plane, the focus sensitivity (the movement amount of the image plane position when the focus lens moves by the unit movement amount) is also lowered. Cheap. Therefore, a strong positive power is inevitably required for the third lens group, and it is difficult to suppress the axial thickness of the third lens group.

Examples described in Patent Document 1, Patent Document 2, and Patent Document 3 are examples in which the second lens group and the third lens group move to the object side by zooming to the long focal point side while reducing the number of components. It has been known.
JP 2000-284177 A, JP 2001-242378 A, Japanese Patent No. 3,513,369

  However, any of the above lens systems has a long overall length when used, and the thickness of each group is large, which is disadvantageous for thinning when retracted.

  In addition, the distance between the third lens group and the second lens group at the wide-angle end or the telephoto end is large, which is disadvantageous for reducing the diameter of the third lens group.

  In addition, in Patent Document 1 and Patent Document 2, the distance between the second lens group and the third lens group is substantially constant from the wide-angle end to the telephoto end. It is difficult to make fine adjustments.

  The present invention has been made in view of such problems in the prior art, and its purpose is to achieve an appropriate zoom ratio without bending the optical axis or retracting some lens groups outside the optical axis. It is possible to provide a zoom lens that can be secured, which is advantageous for ensuring miniaturization and optical performance, and an imaging device using the zoom lens.

The zoom lens according to the present invention includes, in order from the object side, three lens groups including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. A zoom lens in which an interval between the lens group and the second lens group changes during zooming, and an interval between the second lens group and the third lens group changes during zooming or focusing operation;
At least the second lens group and the third lens group from the wide-angle end to the telephoto end so that the distance between the first lens group and the second lens group becomes narrower in the telephoto end state than in the wide-angle end state. Move only to the object side when scaling to
The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side.
The second lens group consists of three lenses,
The third lens group is composed of one positive lens,
The following conditional expression is satisfied.

0.45 <Σd _1G / f _w <0.65 (1)
Where Σd _1G : thickness of the first lens group on the optical axis,
f _w : Focal length at the wide-angle end of the zoom lens,
It is.

Another zoom lens according to the present invention includes three lens groups 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 having a positive refractive power, A zoom lens in which an interval between the first lens group and the second lens group changes at the time of zooming, and an interval between the second lens group and the third lens group changes at the time of zooming,
At least when the second lens group is zoomed from the wide-angle end to the telephoto end so that the distance between the first lens group and the second lens group is narrower in the telephoto end state than in the wide-angle end state. Move only to the side, and
The third lens group moves so as to be positioned closer to the object side at the telephoto end than at the wide angle end;
The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side.
The second lens group consists of three lenses,
The third lens group is composed of one positive lens,
The following conditional expression is satisfied.

0.04 <D ₂ (w) / f ₃ <0.23 (2)
0.04 <D ₂ (t) / f ₃ <0.23 (3)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
f ₃ : focal length of the third lens group,
It is.

Still another zoom lens of the present invention is composed of three lens groups 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 having a positive refractive power, A zoom lens in which an interval between the first lens group and the second lens group changes at the time of zooming, and an interval between the second lens group and the third lens group changes at the time of zooming or during a focusing operation. ,
At least when the second lens group is zoomed from the wide-angle end to the telephoto end so that the distance between the first lens group and the second lens group is narrower in the telephoto end state than in the wide-angle end state. Move only to the side, and
The third lens group moves so as to be positioned closer to the object side at the telephoto end than at the wide angle end;
The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side.
The second lens group consists of three lenses,
The third lens group is composed of one positive lens,
The following conditional expression is satisfied.

0.04 <D ₂ / f ₃ <0.18 (4)
Where D ₂ is the air spacing on the optical axis between the second lens group and the third lens group in any state from the wide-angle end to the telephoto end.
f ₃ : focal length of the third lens group,
It is.

  Hereinafter, the reason and operation of the zoom lens according to the present invention will be described.

The present invention described above is common, and is composed of three lens groups 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 having a positive refractive power, A zoom lens in which an interval between the first lens group and the second lens group changes during zooming, and an interval between the second lens group and the third lens group changes during zooming or focusing operation;
At least when the second lens group is zoomed from the wide-angle end to the telephoto end so that the distance between the first lens group and the second lens group is narrower in the telephoto end state than in the wide-angle end state. Move only to the side,
The third lens group is positioned closer to the object side at the telephoto end than the wide-angle end, and the third lens group is moved closer to the object side at the telephoto end than the wide-angle end;
The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side.
The second lens group consists of three lenses,
The third lens group is composed of one positive lens.

  With this configuration, in the present invention, the configuration length of each lens group is reduced, and the zoom movable range with respect to the entire length is secured, thereby reducing the burden of the power configuration of each lens group, and reducing the thickness and performance. Are both compatible.

  In other words, the third lens group moves toward the object side at the time of zooming to the telephoto end, so that the beam height of the third lens group is higher than when the third lens group is fixed at the time of zooming or moved toward the image side. Can be kept low. Therefore, the diameter of the third lens group can be reduced. Further, it is possible to suppress the deterioration of performance due to zooming by moving the third lens group.

  In order to achieve both the miniaturization and the optical performance adjustment function, the third lens group is composed of one positive lens. As a result, a zoom movable region can be secured, and further reduction in thickness can be achieved.

  In addition, by making the distance between the third lens group and the second lens group variable during zooming or during focusing operation, it is possible to suppress aberration fluctuations during zooming and the number of moving lenses during focusing.

  In addition, by configuring the first lens group with two lenses, a negative lens and a positive lens, the length of the first lens group can be reduced while maintaining the performance. Thereby, it is possible to widen the zoom movable range while making the lens frame thinner.

  In addition, the second lens group has a main zooming function. By configuring the second lens group with three lenses, the length of the second lens group can be reduced while maintaining the performance. When the second lens group is composed of two lenses, the distance between both lenses tends to be large, particularly for correcting off-axis aberrations. On the other hand, it is difficult to reduce the thickness, or the structure after the third lens group is complicated. Will be necessary and will increase in size as a whole.

  In the case of a lens barrel structure that retracts, etc., this configuration is advantageous because the configuration length of each lens group can be shortened.

  In addition, when the focusing operation is performed by moving the third lens group, an effect of suppressing an increase in the total length can be obtained. At this time, since the third lens group is positioned closer to the object side at the telephoto end than at the wide-angle end, the focus sensitivity at the telephoto can be increased and the power of the third lens group can be reduced. This is advantageous in reducing the thickness of the lens barrel when retracted.

  Furthermore, since the third lens group has a small diameter and is composed of one lens, the weight of the lens can be suppressed, the drive system can be simplified, and the lens frame can be reduced in size.

  It is more preferable that the lenses of the third lens group are made of plastic and reduced in weight.

  In the first aspect of the present invention, the third lens group is configured to move only to the object side upon zooming from the wide-angle end to the telephoto end, which is advantageous for downsizing the third lens group.

  Further, in order to balance the thinning and the aberration, the conditional expression (1) is satisfied.

  Conditional expression (1) defines the thickness of the first lens group on the optical axis. That is, when the upper limit of conditional expression (1) is 0.65 or more, the collapsed thickness increases. Below the lower limit of 0.45, it becomes difficult to correct field curvature and the like.

  In the second (claim 2) of the present invention, the conditional expressions (2) and (3) of the air distance on the optical axis between the second lens group and the third lens group and the focal length of the third lens group are satisfied. Like to do.

  In the present invention, the second lens group has a three-lens configuration, and the third lens group has a one-lens configuration. In this case, by satisfying conditional expressions (2) and (3), the power of the third lens group can be relaxed or the diameter can be easily reduced. Exceeding the lower limits of conditional expressions (2) and (3), 0.04 and 0.04, respectively, makes it difficult to correct off-axis aberrations (especially at telephoto) and increases the power of the third lens group. It is required to make the configuration complicated. Exceeding the upper limits of conditional expressions (2) and (3), respectively 0.23 and 0.23, is not preferable because the entire length of the entire system becomes long (especially at the wide angle end).

  In the case of a lens barrel structure that retracts, etc., this configuration is advantageous because the configuration length of each lens group can be shortened.

  Moreover, the effect which suppresses the increase in a full length can also be acquired by making focusing into a 3rd lens group. At this time, it is desirable that the conditional expressions (2) and (3) are satisfied even in the configuration. When the lower limit is exceeded, there is no allowance for feeding, and the photographing performance of a short-distance subject deteriorates. If the upper limit is exceeded, the focus sensitivity becomes dull, the driving system for focusing becomes large, and the power consumption increases.

  In the third aspect of the present invention, the distance between the second lens group and the third lens group changes at the time of zooming and satisfies the conditional expressions (2) and (3).

  By changing the distance between the second lens group and the third lens group at the time of zooming, this variable gap has a floating function, which is advantageous for suppressing aberration fluctuations at the time of zooming.

  By configuring the variable interval so as to satisfy the conditional expressions (2) and (3), as described above, aberration correction is performed while suppressing the total length, and the second lens group is moved to the focusing movement group. This is advantageous for downsizing.

  In the fourth and fifth aspects of the present invention, the conditional expression (4) is satisfied.

  In the present invention, the second lens group has a three-lens configuration, and the third lens group has a one-lens configuration. In this case, by satisfying conditional expression (4), the power of the third lens group can be relaxed or the diameter can be easily reduced. If the lower limit of 0.04 in conditional expression (4) is exceeded, it will be difficult to correct off-axis aberrations, and it will be necessary to increase the power of the third lens group or to complicate the configuration. Exceeding the upper limit of 0.18 is not preferable because the total length of the entire system becomes long.

  In the case of a lens barrel structure that retracts, etc., this configuration is advantageous because the configuration length of each lens group can be shortened.

  Moreover, the effect which suppresses the increase in a full length can also be acquired by making focusing into a 3rd lens group. At this time, it is desirable that the configuration satisfies the conditional expression (4), and if the lower limit is exceeded, there is no allowance for feeding, and the photographing performance of a short-distance subject deteriorates. If the upper limit is exceeded, the focus sensitivity becomes dull, the driving system for focusing becomes large, and the power consumption increases.

  In the sixth aspect of the present invention, the following conditional expression (5) for the amount of change in the distance between the second lens group and the third lens group is satisfied.

−0.005 <(D ₂ (t) −D ₂ (w)) / f _w <0.5 (5)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
f _w : Focal length at the wide-angle end of the zoom lens,
It is.

  If the upper limit of 0.5 in conditional expression (5) is exceeded, the beam height of the first lens group at the wide-angle end will increase, leading to an increase in the front lens diameter, and the diameter of the final lens will increase, leading to a reduction in size. Disadvantageous. Further, when the third lens group holding frame is held upright from the second lens group holding frame, the length of the shaft is increased by the amount of movement of the third lens group, which is disadvantageous in terms of thinness in terms of the lens frame structure. . In particular, when a retractable lens frame structure or the like is used, it is difficult to reduce the thickness of the lens frame because the thickness when retracted is limited. If the lower limit of -0.005 of conditional expression (5) is exceeded, it will be difficult to secure a margin for variations in image plane position during manufacturing and a space necessary for focusing.

  In the seventh aspect of the present invention, the second lens group is one cemented lens composed of three lenses.

  In order to achieve a thin lens barrel (lens frame), it is necessary to make the holding lens frame member as thin as possible as well as the lens group. By using only a cemented lens as the configuration of the second lens group, it is only necessary to hold the lens in one place, the thickness of the frame can be reduced, and the zoom movable range can be secured, which is advantageous for thinning. . The effect is particularly great when the lens barrel structure is retracted.

  The eighth aspect of the present invention satisfies the following conditional expression (6) that defines the radius of curvature of the lens surface closest to the image side of the first lens group.

-0.41 <f _w / RDY (R) _L2 <0.41 (6)
Where RDY (R) _L2 : radius of curvature on the optical axis of the lens surface closest to the image side of the first lens group,
It is.

  By satisfying this conditional expression, the image side surface of the first lens unit approaches a flat surface, and the first lens unit can be thinned. In addition, the power on the incident side of the positive lens is reduced, and the occurrence of aberration can be suppressed.

  In the ninth aspect of the present invention, the lens barrel is retracted with the interval between the groups being smaller than that at the wide-angle end.

  The present invention is advantageous in maintaining optical performance while suppressing the thickness of each group. Therefore, it is easy to obtain the effect of reducing the final dimension by retracting.

  In the tenth aspect of the present invention, only the third lens unit moves during focusing.

  The present invention facilitates downsizing the third lens group, and is advantageous for maintaining focus sensitivity. Therefore, when the third lens group is a focus group, the burden on the drive system can be reduced.

  When focusing with the first lens group, it is necessary to consider a short focus space, which is disadvantageous for the thin lens frame. The second lens group is difficult to configure because there is a large variation in aberrations, the focus drive direction changes between the wide-angle side and the telephoto side, and there is a focal length range that requires a significant focus space.

  In the eleventh aspect of the present invention, the distance between the second lens group and the third lens group changes during zooming.

  A slight change in the distance between the second lens group and the third lens group has a floating effect, which is advantageous for suppressing aberration fluctuations during zooming.

  In the twelfth aspect of the present invention, the first lens group moves toward the object side after moving toward the image side upon zooming from the wide-angle end to the telephoto end.

  As a result, the main image position adjustment function can be provided to the first lens group. Also, when the distance between the second and third lens groups changes during zooming, aberrations due to zooming can be suppressed by adjusting the amount of movement.

  In the thirteenth aspect of the present invention, the following conditional expression (7) is satisfied.

1.40 <D ₁ (w) / f _w <2.80 (7)
Where D ₁ (w): the air spacing on the optical axis between the first lens group and the second lens group at the wide-angle end,
f _w : Focal length at the wide-angle end of the zoom lens,
It is.

  This conditional expression is a condition for specifying the distance between the first and second lens groups in the wide-angle end state to improve the balance between miniaturization, high zoom ratio, and ensuring optical performance. By making sure that the lower limit of 1.40 is not exceeded, it is advantageous to maintain a variable distance and secure a zoom ratio without increasing the refractive power of the first and second lens units excessively. This is advantageous for aberration correction and maintaining the zoom ratio. By not exceeding the upper limit of 2.80, it is advantageous to suppress an increase in the light beam height in the first lens group and to suppress an increase in the front lens diameter. Alternatively, the increase in the total length is suppressed, which is advantageous for making the lens frame thinner when retracted.

  In the fourteenth aspect of the present invention (14), the following conditional expression (8) is satisfied.

0.5 <D ₂ (t) / D ₂ (w) <2.0 (8)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
It is.

  This conditional expression prescribes conditions for a preferable change in the distance between the second and third lens groups when the third lens group is a focusing lens group.

  By making sure that the lower limit of 0.5 is not exceeded, the telephoto type group interval comprised of the first and second lens group synthesis system and the negative third lens group is maintained, and the telephoto end This is advantageous for shortening the overall length. By not exceeding the upper limit of 2.0, the amount of focus movement by the third lens group during close-up shooting can be suppressed, which is advantageous for thinning the lens frame.

  In the fifteenth aspect of the present invention, the second lens group includes a positive lens and a negative lens.

  Such a configuration is advantageous for adjusting chromatic aberration and principal points in the second lens group.

  Further, as in the sixteenth aspect of the present invention (claim 16), the second lens group includes one cemented lens composed of three lenses of a positive lens, a negative lens, and a positive lens in order from the object side. This is advantageous in reducing the aberration of the second lens group itself.

  Further, the incident side surface of the cemented lens has a positive refracting power on the optical axis, and the refractive power decreases as the distance from the optical axis increases, thereby ensuring the positive refracting power of the second lens group. It is advantageous for correcting spherical aberration that is likely to occur on this surface while securing a zoom ratio by moving the lens closer to the object side.

  In addition, the exit side surface of the cemented lens has a shape in which the refractive power decreases toward the periphery (the positive refractive power decreases or the negative refractive power increases), which is advantageous for correcting curvature of field.

  Further, if the Abbe number of the negative lens in the cemented lens is smaller than the Abbe number of any positive lens in the cemented lens, and the cemented surface is a concave surface of the negative lens, the cemented surface has a negative refractive power. Correction of chromatic aberration can be performed satisfactorily.

  In other words, spherical aberration is mainly caused by the object-side lens surface of the cemented lens, chromatic aberration is mainly controlled by the power and Abbe number rather than the surface shape of the negative lens in the middle, and mainly off-axis by the lens surface on the image side. Aberration control can be realized. Although it is not main, naturally there is also an effect of aberration control at the joint surface, so it is preferable to use it together with the above main effect.

  Further, as in the seventeenth aspect of the present invention, the second lens group includes, from the object side, a single lens having a positive refractive power, and a single cemented lens including a positive lens and a negative lens. It is good.

  With such a configuration, the principal point of the second lens group can be easily moved closer to the object, which is advantageous for increasing the zoom ratio while suppressing the total length of the telephoto end. It is also advantageous for reducing the diameter of the second lens group. In addition, the above-described effect of joining the positive lens and the negative lens can be obtained.

  Further, if the single lens of the second lens group is a lens having a refractive power on the object side that is larger than the refractive power on the image side, a high zoom ratio is obtained by adjusting the principal point, and the second due to the convergence effect of the axial light beam. This is advantageous for reducing the size of the lens group.

  Further, if the image side surface of the cemented lens is a concave surface, it is advantageous for canceling various aberrations caused by the third lens unit having a positive refractive power.

  In the eighteenth aspect (18th aspect) of the present invention, the following conditional expression (9) is satisfied with respect to the focal length of the third lens unit.

3.8 <f ₃ / f _w <15.0 (9)
Where f _{3 is} the focal length of the third lens group,
f _w : Focal length at the wide-angle end of the zoom lens,
It is.

  In the present invention, the third lens unit is advantageously reduced in size by the moving method of the third lens unit. When the third lens group is a focus lens group, the focus sensitivity of the third lens group at the telephoto end is easily increased, so that the refractive power of the third lens group satisfies the conditional expression (9). It can be made reasonably small, which is advantageous for further downsizing. By making sure that the lower limit of 3.8 of conditional expression (9) is not exceeded, the amount of movement of the third lens unit during focusing is suppressed, which is advantageous for thinning. By making it not exceed the upper limit of 15.0, the refractive power in the third lens group can be suppressed, and the influence on the aberration can be easily reduced.

  In the nineteenth (claim 19) of the present invention, the following conditional expression (10) is satisfied.

0.01 <D _3G / _ft <0.08 (10)
Where D _3G : is the thickness on the axis of the third lens group,
f _t : focal length of the zoom lens in the telephoto end state,
It is.

  It is preferable that the above conditional expression (10) is satisfied so that the third lens group becomes a thick positive lens having an appropriate thickness. By making sure that the lower limit of 0.01 of this conditional expression is not exceeded, it is advantageous to ensure the strength of the positive lens necessary for the third lens group. By not exceeding the upper limit of 0.08, the axial thickness of the third lens group is suppressed, which is advantageous in reducing the size of the zoom lens when retracted.

  As in the twentieth aspect of the present invention, it is preferable that the following conditional expression (A) is satisfied.

2.5 ≦ f _t / f _w <5.5 (A)
Where f _t : focal length of the zoom lens in the telephoto end state,
f _w : Focal length at the wide-angle end of the zoom lens,
It is.

  The present invention is preferably a zoom lens having an appropriate zoom ratio of 2.5 or more, since it is easy to balance the size of the entire system and the optical performance. If the lower limit of 2.5 of conditional expression (A) is not exceeded, the zoom ratio in general use is satisfied. If the upper limit of 5.5 is not exceeded, an increase in the number of lenses for correcting aberrations is suppressed, which is advantageous for cost reduction.

  Further, as in the twenty-first (claim 21) of the present invention, a configuration is provided in which an aperture stop is disposed immediately before the second lens group and moves integrally with the second lens group at the time of zooming. It is preferable.

  With this configuration, an increase in the diameter of the first lens group can be prevented, and the off-axis principal ray emitted from the third lens group can be easily made parallel to the optical axis. In addition, since there is no second lens group on the object side of the aperture stop and the lenses of the second lens group are concentrated on the image side of the aperture stop, aberration deterioration due to relative decentration of the lenses in the second lens group is also caused. It can be configured to be suppressed. Further, the moving mechanism of the aperture stop can be shared with the second lens group, and the configuration can be easily simplified.

  Further, as in the twenty-second aspect of the present invention, it is preferable that the zoom lens according to any one of the present invention described above and an image pickup element arranged on the image side and converting an optical image into an electric signal are provided. .

  The zoom lens of the present invention is advantageous for downsizing and securing a field angle at the wide-angle end. Moreover, since it is easy to suppress the change of the incident angle of the light ray on the imaging surface, it is preferable to use the imaging device having the above-described imaging device.

  Each of the above-described inventions may arbitrarily satisfy a plurality at the same time, whereby a better effect can be obtained.

  Moreover, it is good also as a structure which made the component requirement described dependent on the specific invention dependent on another structure.

  Further, if each conditional expression is satisfied by being arbitrarily combined, a better effect can be obtained.

  Moreover, in order to make the above-mentioned effect better, each conditional expression is preferably configured as follows.

  For conditional expression (1), it is more preferable to set the lower limit value to 0.50, and further to 0.55.

  Further, it is more preferable that the upper limit value is 0.63.

  For conditional expression (5), it is more preferable to set the lower limit to −0.003.

  Further, it is more preferable that the upper limit value is 0.4, further 0.3.

  For conditional expression (6), it is more preferable to set the lower limit to −0.40, and more preferably to −0.38.

  Further, it is more preferable that the upper limit value is 0.40, further 0.38.

  For conditional expression (7), it is more preferable to set the lower limit to 1.5.

  Further, the upper limit value is more preferably 2.5, and further preferably 2.2.

  For conditional expression (8), it is more preferable to set the lower limit to 0.6.

  Further, it is more preferable that the upper limit value is 1.5.

  For conditional expression (9), it is more preferable to set the lower limit to 3.9.

  Further, it is more preferable that the upper limit value is 10.0, further 7.0.

  For conditional expression (10), it is more preferable that the lower limit value be 0.03.

  In conditional expression (A), it is more preferable that the lower limit value is 2.6, and further 2.7.

  Further, it is more preferable that the upper limit value is 4.5, further 3.5.

  According to the present invention as described above, it is possible to secure an appropriate zoom ratio without bending the optical axis or retracting a part of the lens group to the outside of the optical axis, and it is advantageous for downsizing and ensuring optical performance. An imaging device using can be obtained.

Examples 1 to 7 of the zoom lens according to the present invention will be described below. FIGS. 1 to 7 show lens cross-sectional views at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 7, respectively. In the figure, the first lens group is G1, the aperture stop is S, the second lens group is G2, the third lens group is G3, the parallel plate constituting the low-pass filter with IR cut coating, etc. is F, the electronic imaging element ( The parallel plate of the cover glass of CCD or CMOS) is indicated by C, and the image plane (light receiving surface of the electronic image sensor) is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action.
In addition, Example 5 in Examples 1-7 is a reference example.

  As shown in FIG. 1, the zoom lens according to the first embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly widening the distance from 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, and the second lens group G2 includes a positive meniscus lens having a convex surface directed toward the object side and an object. The third lens group G3 is composed of one positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspheric surfaces are the image side surface of the biconcave negative lens of the first lens group G1, the most object side surface and the most image side surface of the three-junction lens of the second lens group G2, and the positive surface of the third lens group G3. It is used for four surfaces on the object side of the meniscus lens.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly widening the distance from 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, and the second lens group G2 includes a positive meniscus lens having a convex surface directed toward the object side and an object. The third lens group G3 is composed of one positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspheric surfaces are the image side surface of the biconcave negative lens of the first lens group G1, the most object side surface and the most image side surface of the three-junction lens of the second lens group G2, and the positive surface of the third lens group G3. It is used for four surfaces on the object side of the meniscus lens.

  As shown in FIG. 3, the zoom lens according to the third embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly widening the distance from the second lens group G2.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. The third lens group G3 is composed of a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. Consists of a single lens. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspheric surfaces are both surfaces of the positive meniscus lens of the first lens group G1, the most object side surface and the most image side surface of the triplet cemented lens of the second lens group G2, and both surfaces of the positive meniscus lens of the third lens group G3. It is used for 6 sides.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly increasing the distance from the second lens group G2 and then slightly reducing it.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. The third lens group G3 is composed of a positive meniscus lens having a convex surface facing the object side, a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. Consists of a single lens. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspherical surfaces are used on both surfaces of the positive meniscus lens of the first lens group G1, and on the four surfaces of the most cemented lens in the second lens group G2, the most object side surface and the most image side surface.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while widening the distance from 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 facing the object side, and the second lens group G2 has a biconvex positive lens and a convex surface facing the object side. The third lens group G3 is composed of one biconvex positive lens. The cemented lens is a positive meniscus lens and a negative meniscus lens having a convex surface facing the object side. The aperture stop S is located closer to the image side than the object side surface of the biconvex positive lens of the second lens group G2.

  The aspheric surfaces are 4 on the image side surface of the biconcave negative lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the object side surface of the biconvex positive lens of the third lens group G3. Used on the surface.

  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, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly reducing the distance from 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, and the second lens group G2 includes a positive meniscus lens having a convex surface directed toward the object side and an object. The third lens group G3 is composed of one positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspheric surfaces are the image side surface of the biconcave negative lens of the first lens group G1, the most object side surface and the most image side surface of the three-junction lens of the second lens group G2, and the positive surface of the third lens group G3. Used on both sides of the meniscus lens.

  As shown in FIG. 7, the zoom lens according to the seventh embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. Consists of a lens group G3. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves along a locus convex toward the image side. Located on the side. The aperture stop S and the second lens group G2 move monotonously toward the object side while integrally reducing the distance between the first lens group G1. The third lens group G3 moves toward the object side while slightly increasing the distance from the second lens group G2 and then slightly reducing it.

  In order from the object side, the first lens group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 has a convex surface facing the object side. The third lens group G3 is composed of one biconvex positive lens. The positive lens is a positive meniscus lens, a negative meniscus lens having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is positioned on the image side of the most object side surface of the three-piece cemented lens of the second lens group G2.

  The aspheric surfaces are the image side surface of the negative meniscus lens and the object side surface of the positive meniscus lens of the first lens group G1, and the most object side surface and the most image side surface of the three-junction lens of the second lens group G2. And 6 surfaces on both sides of the biconvex positive lens of the third lens group G3.

  In any of the above embodiments, focusing is performed by moving the third lens group G3.

Hereinafter, numerical data of each embodiment described above, but the symbols are outside the above, f is the focal length, F _NO is the F-number, 2 [omega is field angle, WE denotes a wide angle end, ST intermediate state, TE is The telephoto end, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, d ₁ , d ₂ ... _Are the distances between the lens surfaces, n _d1 , n _d2 are the refractive index of the d-line of each lens, ν _d1 , ν _d2 ... is the Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

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

Example 1
r ₁ = -55.947 d ₁ = 0.90 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 6.646 (aspherical surface) d ₂ = 1.62
r ₃ = 11.161 d ₃ = 1.82 n _d2 = 2.00069 ν _d2 = 25.46
r ₄ = 30.512 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.67
r ₆ = 5.808 (aspherical surface) d ₆ = 3.51 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = 16.319 d ₇ = 0.60 n _d4 = 1.84666 ν _d4 = 23.78
r ₈ = 5.200 d ₈ = 1.36 n _d5 = 1.58313 ν _d5 = 59.38
r ₉ = 26.430 (aspherical surface) d ₉ = (variable)
r ₁₀ = 24.745 (aspherical surface) d ₁₀ = 1.24 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₁ = 7929.558 d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.45
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -3.702
A ₄ = 1.29210 × 10 ^-3
A ₆ = -2.94031 × 10 ^-5
A ₈ = 6.63852 × 10 ^-7
A ₁₀ = -7.48401 × 10 ^-9
6th surface K = -2.011
A ₄ = 1.29270 × 10 ^-3
A ₆ = -8.81428 × 10 ^-6
A ₈ = 1.57107 × 10 ^-6
A ₁₀ = -3.88466 × 10 ^-8
Surface 9 K = 0.000
A ₄ = 1.94125 × 10 ^-3
A ₆ = 3.03189 × 10 ^-5
A ₈ = 1.16357 × 10 ^-5
A ₁₀ = 1.55401 × 10 ^-7
10th surface K = 0.000
A ₄ = -1.01517 × 10 ^-4
A ₆ = 5.70765 × 10 ^-6
A ₈ = 0
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 7.51 14.60 21.63
F _NO 2.88 3.86 4.84
2ω (°) 70.01 35.27 23.89
d ₄ 15.42 4.74 1.07
d ₉ 4.10 4.19 4.41
d ₁₁ 6.29 11.60 16.79.

Example 2
r ₁ = -200.434 d ₁ = 0.90 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 6.474 (aspherical surface) d ₂ = 1.53
r ₃ = 9.933 d ₃ = 2.02 n _d2 = 2.00069 ν _d2 = 25.46
r ₄ = 21.902 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.63
r ₆ = 5.753 (aspherical surface) d ₆ = 2.06 n _d3 = 1.80610 ν _d3 = 40.92
r ₇ = 35.230 d ₇ = 1.27 n _d4 = 1.84666 ν _d4 = 23.78
r ₈ = 5.202 d ₈ = 2.06 n _d5 = 1.58313 ν _d5 = 59.38
r ₉ = 16.552 (aspherical surface) d ₉ = (variable)
r ₁₀ = 14.000 (aspherical surface) d ₁₀ = 1.24 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₁ = 41.056 d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.43
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -3.501
A ₄ = 1.39590 × 10 ^-3
A ₆ = -2.94154 × 10 ^-5
A ₈ = 6.73010 × 10 ^-7
A ₁₀ = -7.13429 × 10 ^-9
6th page K = -2.429
A ₄ = 1.61259 × 10 ^-3
A ₆ = -1.94631 × 10 ^-5
A ₈ = 2.01443 × 10 ^-6
A ₁₀ = -5.44542 × 10 ^-8
Surface 9 K = -4.333
A ₄ = 2.27790 × 10 ^-3
A ₆ = 1.03782 × 10 ^-5
A ₈ = 2.09837 × 10 ^-5
A ₁₀ = -4.69417 × 10 ^-7
10th surface K = 0.000
A ₄ = -1.47199 × 10 ^-4
A ₆ = 5.67379 × 10 ^-6
A ₈ = 4.82046 × 10 ^-7
A ₁₀ = -1.84788 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 7.51 14.38 21.64
F _NO 2.88 3.78 4.75
2ω (°) 69.34 35.82 23.90
d ₄ 16.35 5.11 1.03
d ₉ 4.20 4.23 4.65
d ₁₁ 5.83 10.66 15.58.

Example 3
r ₁ = 19.064 d ₁ = 0.80 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 5.104 d ₂ = 1.87
r ₃ = 10.613 (aspherical surface) d ₃ = 1.50 n _d2 = 1.82114 ν _d2 = 24.06
r ₄ = 17.740 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.50
r ₆ = 4.218 (aspherical surface) d ₆ = 1.25 n _d3 = 1.80610 ν _d3 = 40.92
r ₇ = 16.475 d ₇ = 0.50 n _d4 = 1.72825 ν _d4 = 28.46
r ₈ = 3.000 d ₈ = 1.98 n _d5 = 1.58313 ν _d5 = 59.38
r ₉ = 6.705 (aspherical surface) d ₉ = (variable)
r ₁₀ = 15.406 (aspherical surface) d ₁₀ = 1.20 n _d6 = 1.52511 ν _d6 = 56.22
r ₁₁ = 679.942 (aspherical surface) d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.40
r ₁₆ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -13.399
A ₄ = 1.00692 × 10 ^-3
A ₆ = -5.17345 × 10 ^-5
A ₈ = 2.70682 × 10 ^-6
A ₁₀ = -8.69858 × 10 ^-8
4th surface K = 4.762
A ₄ = -9.39622 × 10 ^-4
A ₆ = 1.08563 × 10 ^-5
A ₈ = -5.52833 × 10 ^-7
A ₁₀ = -3.72262 × 10 ^-8
6th surface K = -1.661
A ₄ = 2.81854 × 10 ^-3
A ₆ = 3.99977 × 10 ^-5
A ₈ = 1.43030 × 10 ^-6
A ₁₀ = 1.39779 × 10 ^-7
Surface 9 K = -1.556
A ₄ = 5.79158 × 10 ^-3
A ₆ = 5.27276 × 10 ^-4
A ₈ = 2.64149 × 10 ^-7
A ₁₀ = 1.62265 × 10 ^-5
Surface 10 K = -14.699
A ₄ = 1.27364 × 10 ^-3
A ₆ = 1.39733 × 10 ^-4
A ₈ = 2.54309 × 10 ^-5
A ₁₀ = -7.92228 × 10 ^-7
11th surface K = 0.000
A ₄ = 6.13478 × 10 ^-4
A ₆ = 1.52095 × 10 ^-4
A ₈ = 7.94767 × 10 ^-6
A ₁₀ = 1.36613 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 6.61 12.75 19.11
F _NO 3.48 4.64 5.80
2ω (°) 62.40 33.44 22.45
d ₄ 13.97 4.45 0.90
d ₉ 2.98 3.71 3.63
d ₁₁ 5.54 9.39 13.94.

Example 4
r ₁ = 69.726 d ₁ = 0.50 n _d1 = 1.69350 ν _d1 = 53.21
r ₂ = 4.746 d ₂ = 1.96
r ₃ = 12.885 (aspherical surface) d ₃ = 1.36 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 25.844 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.50
r ₆ = 4.943 (aspherical surface) d ₆ = 3.04 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = 25.950 d ₇ = 0.50 n _d4 = 1.71736 ν _d4 = 29.52
r ₈ = 3.545 d ₈ = 1.57 n _d5 = 1.51633 ν _d5 = 64.14
r ₉ = -140.225 (aspherical surface) d ₉ = (variable)
r ₁₀ = 36.103 d ₁₀ = 1.08 n _d6 = 1.58393 ν _d6 = 30.21
r ₁₁ = 157.196 d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.60
r ₁₆ = ∞ (image plane)
Aspheric coefficient 3rd surface K = 2.135
A ₄ = -3.15464 × 10 ^-4
A ₆ = -1.04123 × 10 ^-5
A ₈ = -2.90693 × 10 ^-7
A ₁₀ = 0
4th surface K = -1.605
A ₄ = -6.13441 × 10 ^-4
A ₆ = -1.89803 × 10 ^-5
A ₈ = -5.74661 × 10 ^-7
A ₁₀ = 0
6th surface K = -1.070
A ₄ = 9.28135 × 10 ^-4
A ₆ = 1.60749 × 10 ^-5
A ₈ = 9.55801 × 10 ^-7
A ₁₀ = 0
Surface 9 K = 0.000
A ₄ = 2.77025 × 10 ^-3
A ₆ = 8.45677 × 10 ^-5
A ₈ = 2.81700 × 10 ^-5
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.11 11.77 17.64
F _NO 3.24 4.42 5.65
2ω (°) 70.69 36.52 24.36
d ₄ 10.68 3.49 0.90
d ₉ 3.68 3.69 3.68
d ₁₁ 4.04 8.76 13.77.

Example 5
r ₁ = -160.146 d ₁ = 0.90 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 7.098 (aspherical surface) d ₂ = 1.65
r ₃ = 10.592 d ₃ = 2.00 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 26.737 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.50
r ₆ = 6.763 (aspherical surface) d ₆ = 2.00 n _d3 = 1.58913 ν _d3 = 61.25
r ₇ = -36.924 (aspherical surface) d ₇ = 0.10
r ₈ = 5.800 d ₈ = 1.50 n _d4 = 1.74320 ν _d4 = 49.34
r ₉ = 8.590 d ₉ = 0.55 n _d5 = 1.84666 ν _d5 = 23.78
r ₁₀ = 3.731 d ₁₀ = (variable)
r ₁₁ = 18.510 (aspherical surface) d ₁₁ = 1.70 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -100.022 d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.50 n _d7 = 1.54771 ν _d7 = 62.84
r ₁₄ = ∞ d ₁₄ = 0.50
r ₁₅ = ∞ d ₁₅ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₆ = ∞ d ₁₆ = 0.47
r ₁₇ = ∞ (image plane)
Aspheric coefficient 2nd surface K = 0.451
A ₄ = -3.50597 × 10 ^-4
A ₆ = 1.68189 × 10 ^-6
A ₈ = -9.27265 × 10 ^-7
A ₁₀ = 3.65434 × 10 ^-8
A ₁₂ = -8.50610 × 10 ^-10
6th surface K = -0.342
A ₄ = -3.00803 × 10 ^-4
A ₆ = 1.21000 × 10 ^-5
A ₈ = -1.61039 × 10 ^-6
A ₁₀ = 0
A ₁₂ = 0
Surface 7 K = -16.702
A ₄ = -1.08960 × 10 ^-4
A ₆ = 1.42203 × 10 ^-5
A ₈ = -1.79719 × 10 ^-6
A ₁₀ = 0
A ₁₂ = 0
11th surface K = -12.387
A ₄ = 2.18644 × 10 ^-4
A ₆ = 5.62619 × 10 ^-6
A ₈ = 0
A ₁₀ = 0
A ₁₂ = 0
Zoom data (∞)
WE ST TE
f (mm) 7.51 12.27 21.75
F _NO 2.85 3.47 4.70
2ω (°) 69.50 41.96 23.85
d ₄ 16.82 7.45 0.90
d ₁₀ 4.71 5.24 6.22
d ₁₂ 5.48 8.53 14.96.

Example 6
r ₁ = -2679.606 d ₁ = 1.00 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 3.719 (aspherical surface) d ₂ = 1.02
r ₃ = 5.756 d ₃ = 2.10 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 13.814 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.50
r ₆ = 3.765 (aspherical surface) d ₆ = 1.00 n _d3 = 1.80610 ν _d3 = 40.92
r ₇ = 15.152 d ₇ = 0.50 n _d4 = 1.76182 ν _d4 = 26.52
r ₈ = 3.002 d ₈ = 1.88 n _d5 = 1.51633 ν _d5 = 64.14
r ₉ = 12.981 (aspherical surface) d ₉ = (variable)
r ₁₀ = 6.725 (aspherical surface) d ₁₀ = 1.00 n _d6 = 1.52511 ν _d6 = 56.23
r ₁₁ = 13.188 (aspherical surface) d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.39
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.809
A ₄ = 8.14420 × 10 ^-4
A ₆ = 2.31684 × 10 ^-6
A ₈ = -2.63770 × 10 ^-8
A ₁₀ = 0
6th surface K = -0.759
A ₄ = 1.33919 × 10 ^-3
A ₆ = 7.55420 × 10 ^-5
A ₈ = 1.15979 × 10 ^-6
A ₁₀ = 3.88227 × 10 ^-7
Surface 9 K = 0.000
A ₄ = 2.77245 × 10 ^-3
A ₆ = 6.32079 × 10 ^-4
A ₈ = -5.51581 × 10 ^-5
A ₁₀ = 2.88512 × 10 ^-5
10th surface K = 0.000
A ₄ = -2.56927 × 10 ^-3
A ₆ = -1.07060 × 10 ^-4
A ₈ = 2.26819 × 10 ^-5
A ₁₀ = 9.93781 × 10 ^-7
11th surface K = 0.000
A ₄ = -3.97145 × 10 ^-4
A ₆ = -1.29520 × 10 ^-5
A ₈ = -1.87201 × 10 ^-6
A ₁₀ = 2.25706 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.23 10.00 15.17
F _NO 3.37 4.57 5.90
2ω (°) 79.23 42.60 28.30
d ₄ 8.86 3.04 0.90
d ₉ 2.16 1.72 1.50
d ₁₁ 4.91 9.10 13.42.

Example 7
r ₁ = 31.493 d ₁ = 1.00 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 4.015 (aspherical surface) d ₂ = 1.36
r ₃ = 6.467 (aspherical surface) d ₃ = 1.80 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 13.950 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.45
r ₆ = 3.743 (aspherical surface) d ₆ = 1.30 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = 20.976 d ₇ = 0.50 n _d4 = 1.71736 ν _d4 = 29.52
r ₈ = 3.002 d ₈ = 2.03 n _d5 = 1.51633 ν _d5 = 64.14
r ₉ = 9.297 (aspherical surface) d ₉ = (variable)
r ₁₀ = 19.045 (aspherical surface) d ₁₀ = 1.00 n _d6 = 1.52511 ν _d6 = 56.23
r ₁₁ = -241.584 (aspherical surface) d ₁₁ = (variable)
r ₁₂ = ∞ d ₁₂ = 0.50 n _d7 = 1.51633 ν _d7 = 64.14
r ₁₃ = ∞ d ₁₃ = 0.50
r ₁₄ = ∞ d ₁₄ = 0.50 n _d8 = 1.51633 ν _d8 = 64.14
r ₁₅ = ∞ d ₁₅ = 0.40
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.788
A ₄ = 5.88309 × 10 ^-4
A ₆ = 1.25094 × 10 ^-5
A ₈ = -6.84764 × 10 ^-8
A ₁₀ = 1.92475 × 10 ^-9
Third side K = 0.000
A ₄ = 2.80805 × 10 ^-10
A ₆ = 7.99547 × 10 ^-7
A ₈ = -3.58622 × 10 ^-12
A ₁₀ = 0
6th surface K = -1.016
A ₄ = 2.19556 × 10 ^-3
A ₆ = 9.52058 × 10 ^-5
A ₈ = 2.20537 × 10 ^-6
A ₁₀ = -7.19757 × 10 ^-8
Surface 9 K = 0.000
A ₄ = 6.49949 × 10 ^-3
A ₆ = 6.51196 × 10 ^-4
A ₈ = 8.19880 × 10 ^-5
A ₁₀ = 1.62716 × 10 ^-5
10th surface K = 0.000
A ₄ = -8.16440 × 10 ^-11
A ₆ = 4.00208 × 10 ^-5
A ₈ = 1.51332 × 10 ^-5
A ₁₀ = 2.94028 × 10 ^-6
11th surface K = 0.000
A ₄ = 7.72945 × 10 ^-7
A ₆ = 5.03191 × 10 ^-5
A ₈ = -1.14557 × 10 ^-5
A ₁₀ = 4.64487 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.53 10.00 16.04
F _NO 3.48 4.49 5.80
2ω (°) 71.60 42.04 26.68
d ₄ 12.20 4.63 0.95
d ₉ 2.50 3.01 2.50
d ₁₁ 4.49 7.40 12.12.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 7 are shown in FIGS. In these aberration diagrams, (a) is the wide angle end, (b) is the intermediate state, (c) is the spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) at the telephoto end. ). In each figure, “FIY” indicates the maximum image height (mm).

  Next, the basic parameter values of the conditional expressions (1) to (10) and (A) and the values of the conditional expressions in the above embodiments will be shown.

Example 1 2 3 4 5 6 7
f _w 7.51 7.51 6.61 6.11 7.51 5.23 5.53
f _t 21.63 21.64 19.11 17.64 21.75 15.17 16.04
Σd _1G 4.34 4.45 4.17 3.81 4.55 4.12 4.16
RDY (R) _L2 30.51 21.90 17.74 25.84 26.74 13.81 13.95
D ₁ (w) 14.76 15.72 13.47 10.18 16.32 8.36 11.75
D ₂ (w) 4.10 4.20 2.98 3.68 4.71 2.16 2.50
D ₂ (Intermediate) 4.19 4.23 3.71 3.69 5.24 1.72 3.01
D ₂ (t) 4.41 4.65 3.63 3.68 6.22 1.50 2.50
f ₃ 47.24 39.80 30.00 80.00 29.88 24.81 33.66
D _3G 1.24 1.24 1.20 1.08 1.70 1.00 1.00
(1) Σd _1G / f _w 0.58 0.59 0.63 0.62 0.61 0.79 0.75
(2) D ₂ (w) / f ₃ 0.087 0.106 0.099 0.046 0.158 0.087 0.074
* D ₂ (intermediate) / f ₃ 0.089 0.106 0.124 0.046 0.175 0.069 0.089
(3) D ₂ (t) / f ₃ 0.093 0.117 0.121 0.046 0.208 0.060 0.074
_{(5) (D 2 (t} ) -D 2 (w)) / f w
0.0411 0.0601 0.0985 -0.0013 0.2009 -0.1253 0.0000 (6) f _w / RDY (R) _L2
0.25 0.34 0.37 0.24 0.28 0.38 0.40
(7) D ₁ (w) / f _w 1.96 2.09 2.04 1.67 2.17 1.60 2.13
(8) D ₂ (t) / D ₂ (w)
1.08 1.11 1.22 1.00 1.32 0.70 1.00
(9) f ₃ / f _w 6.29 5.30 4.54 13.10 3.98 4.74 6.09
_{(10) D 3G / f t} 0.0571 0.0573 0.0628 0.0610 0.0782 0.0659 0.0624 (A) f t / f w 2.88 2.88 2.89 2.89 2.90 2.90 2.90
.

  FIGS. 15 to 21 are cross-sectional views showing the retracted state when the zoom lenses of Examples 1 to 7 are not used, respectively. In any of the embodiments, the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, and the front of the third lens group G3 and the image plane I. Each of the lens groups G1 to G3 is accommodated on the image plane I side by shortening the distance from the parallel flat plate F as much as possible (of course, by shortening from the wide-angle end state).

  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. 22, the magnification on the circumference (image height) of the radius R inscribed in the short 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. 22, a point P ₁ on the circumference of an arbitrary radius r ₁ (ω) positioned 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) = αf tan ω (0 ≦ α ≦ 1)
Here, ω is the half-angle of the subject, and f is the focal length of the imaging optical system (in the present invention, the zoom lens).

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

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

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

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

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

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

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

  Preferably, the radius R satisfies the following conditional expression.

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

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

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

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

  23 to 25 are conceptual diagrams of the configuration of a digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 41. FIG. FIG. 23 is a front perspective view showing the appearance of the digital camera 40, FIG. 24 is a rear front view thereof, and FIG. However, in FIGS. 23 and 25, the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 located on the photographing optical path 42, a finder optical system 43 located on the finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length. When the photographic optical system 41 is retracted, the photographic optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60, including the change button 61, the setting change switch 62, and the like. Then, when the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 enters the non-collapsed state of FIG. 25, and when the shutter button 45 disposed on the upper part of the camera 40 is pressed, the photographing is performed in conjunction therewith. Photographing is performed through the optical system 41, for example, the zoom lens of the first embodiment. An object image formed by the photographic optical system 41 is formed on the imaging surface (photoelectric conversion surface) of the CCD 49 via a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording / writing electronically using a floppy disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

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

  FIG. 26 is a block diagram showing a configuration of an internal circuit of the main part of the digital camera 40. In the following description, the processing unit 51 includes, for example, the CDS / ADC unit 24, the temporary storage memory 17, the image processing unit 18, and the like, and the storage unit 52 includes, for example, the storage medium unit 19 and the like.

  As shown in FIG. 26, the digital camera 40 is connected to the operation unit 12, the control unit 13 connected to the operation unit 12, and the control signal output port of the control unit 13 via buses 14 and 15. An imaging drive circuit 16, a temporary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21 are provided.

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

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

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

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

  The temporary storage memory 17 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 24. The image processing unit 18 reads out the RAW data stored in the temporary storage memory 17 or the RAW data stored in the storage medium unit 19, and performs various corrections including distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs image processing electrically.

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

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

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

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

FIG. 2 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the zoom lens of the present invention. It is the same figure as FIG. 1 of Example 2 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 3 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 6 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 7 of the zoom lens of this invention. 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. 3 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 1 is not used. FIG. 6 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 2 is not used. FIG. 6 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 3 is not used. FIG. 6 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 4 is not used. FIG. 10 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 5 is not used. FIG. 10 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 6 is not used. FIG. 12 is a cross-sectional view illustrating a retracted state when the zoom lens of Example 7 is not used. It is a figure for demonstrating the basic concept for carrying out the digital correction of the distortion of an image. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 24 is a rear perspective view of the digital camera of FIG. 23. It is sectional drawing of the digital camera of FIG. FIG. 24 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 23.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group S ... Aperture stop F ... Low pass filter C ... Cover glass I ... Image plane E ... Observer eyeball 12 ... Operation part 13 ... Control part 14,15 ... bus 16 ... imaging drive circuit 17 ... temporary storage memory 18 ... image processing section 19 ... storage medium section 20 ... display section 21 ... setting information storage memory section 22 ... bus 24 ... CDS / ADC section 40 ... digital camera 41 ... imaging optics System 42 ... Optical path for photographing 43 ... Viewfinder optical system 44 ... Optical path for viewfinder 45 ... Shutter button 46 ... Flash 47 ... Liquid crystal display monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Finder objective optical system 55 ... Erect prism system 55a, 55b, 55c ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focal length Change button 62 ... Setting change switch

Claims (17)

In order from the object side, the lens unit includes three lens groups, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. A zoom lens in which an interval between the second lens group and the third lens group is changed at the time of zooming, and an interval between the second lens group and the third lens group is changed at the time of zooming;
At least the second lens group and the third lens group from the wide-angle end to the telephoto end so that the distance between the first lens group and the second lens group becomes narrower in the telephoto end state than in the wide-angle end state. Move only to the object side when scaling to
The first lens group is composed of two lenses, a negative lens and a positive lens, in order from the object side.
The second lens group consists of one cemented lens composed of three lenses ,
The third lens group is composed of one positive lens,
A zoom lens satisfying the following conditional expression:
0.45 <Σd _1G / f _w <0.65 (1)
Where Σd _1G : thickness of the first lens group on the optical axis,
f _w : Focal length at the wide-angle end of the zoom lens,
It is. Claim 1 zoom lens, wherein the satisfying the expression below.
0.04 <D ₂ (w) / f ₃ <0.23 (2)
0.04 <D ₂ (t) / f ₃ <0.23 (3)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
f ₃ : focal length of the third lens group,
It is. 3. The zoom lens according to claim 1, wherein the following conditional expression is satisfied in any state from the wide-angle end to the telephoto end.
0.04 <D ₂ / f ₃ <0.18 (4)
Where D ₂ is the air spacing on the optical axis between the second lens group and the third lens group in any state from the wide-angle end to the telephoto end.
f ₃ : focal length of the third lens group,
It is. Wherein any one of claims zoom lens of claims 1 to 3, characterized in that distance between the second lens group and the third lens group satisfies the following condition.
−0.005 <(D ₂ (t) −D ₂ (w)) / f _w <0.5 (5)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
It is. Wherein any one of claims zoom lens of claims 1 to 4, the first lens group satisfies the following conditional expression.
-0.41 <f _w / RDY (R) _L2 <0.41 (6)
Where RDY (R) _L2 : radius of curvature on the optical axis of the lens surface closest to the image side of the first lens group,
It is. Any one claim of the zoom lens of claims 1 5, characterized in that than at the wide angle end state to the collapsed to reduce the distance of each lens group. Any one claim of the zoom lens of claims 1 6, characterized in that only the third lens group upon focusing moves. Wherein any one of claims zoom lens of claims 1 to 7, characterized in that the first lens group moves from the wide angle end toward the object side after moving toward the image side during zooming to the telephoto end. The following conditional expression (7) any one of claims zoom lens of claims 1 to 8, characterized by satisfying the.
1.40 <D ₁ (w) / f _w <2.80 (7)
Where D ₁ (w): the air spacing on the optical axis between the first lens group and the second lens group at the wide-angle end,
It is. The zoom lens according to any one of claims 1 to 9, wherein the following conditional expression (8) is satisfied.
0.5 <D ₂ (t) / D ₂ (w) <2.0 (8)
Where D ₂ (w): the air spacing on the optical axis between the second lens group and the third lens group at the wide-angle end,
D ₂ (t): an air interval on the optical axis between the second lens group and the third lens group at the telephoto end,
It is. Any one zoom lens according to claim 1 to 10, wherein the second lens group includes a positive lens and a negative lens. The said 2nd lens group consists of one cemented lens comprised by three lenses, a positive lens, a negative lens, and a positive lens in order from an object side , The any one of Claim 1 to 11 characterized by the above-mentioned. Zoom lens described in the item . The zoom lens according to any one of claims 1 to 12, wherein the third lens group satisfies the following conditional expression (9).
3.8 <f ₃ / f _w <15.0 (9)
Where f _{3 is} the focal length of the third lens group,
It is. The zoom lens according to any one of claims 1 to 13, wherein the third lens group satisfies the following conditional expression (10).
0.01 <D _3G / _ft <0.08 (10)
Where D _3G : is the thickness on the axis of the third lens group,
f _t : focal length of the zoom lens in the telephoto end state,
It is. Any one zoom lens according to claims 1 to 14, characterized in that the following condition is satisfied.
2.5 ≦ f _t / f _w <5.5 (A)
Where f _t : focal length of the zoom lens in the telephoto end state,
It is. 16. The aperture stop according to claim 1, further comprising an aperture stop that is disposed immediately before the second lens group and moves integrally with the second lens group during zooming. Zoom lens. A zoom lens according to any one of claims 1 16, disposed on the image side of the zoom lens, an imaging apparatus characterized by comprising an imaging device that converts an optical image into an electrical signal.

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