JP4873937B2 - Three-group zoom lens and image pickup apparatus including the same - Google Patents

Description

  The present invention relates to a three-group zoom lens and an image pickup apparatus including the same, and particularly to a three-group 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 has been reduced in size by a normal retractable method,
Negative and positive type 2 group zoom lens,
Negative, positive, negative type 3 group zoom lens,
Negative, positive, positive three-group zoom lens,
It has been known.

  Among these, the negative and positive type two-group zoom lens has a small number of lens groups, which is advantageous in reducing the total thickness of the lens frame that directly holds the lens. 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. However, 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 is reverse in the magnification state before and after the same magnification imaging state. It becomes. 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. Therefore, the first lens group is moved for focusing or the entire zoom lens is moved, leading 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. Disadvantageous.

  In addition, the negative, positive, and negative type three-group zoom lens is advantageous for downsizing because the front lens diameter can be reduced. However, it is difficult to brighten the F number, and the incident angle to the image pickup device becomes large and is susceptible to shading.

  Although it is advantageous for downsizing, the image is enlarged by the negative lens group on the image side, so that it is easily affected by manufacturing errors and it is difficult to obtain stable optical performance.

  On the other hand, a negative, positive, and positive type three-group zoom lens is advantageous in that stable optical performance can be easily obtained and the increase in total length can be suppressed by performing focusing in the third lens group.

  Among the negative, positive, and positive three-group zoom lenses, it is generally known that the third lens group moves toward the image side at the telephoto end with respect to the wide-angle end or does not move substantially due to the zooming operation. Yes. 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 becomes high, which is disadvantageous for reducing the lens diameter. It becomes. In addition, since the focus sensitivity (the amount of movement of the image plane position when the focus lens moves by the unit movement amount) tends to be low, the third lens group inevitably requires a strong power, and the lens diameter. The lens thickness tends to increase due to the balance between the two.

Further, as examples in which the third lens group moves toward the object side during zooming to the telephoto end, Patent Documents 1 to 4 are used.
Those described in (1) are known.
JP 2000-284177 A JP 2001-242378 A Patent 3,513,369 gazette Example 3, 4 Japanese Patent No. 3,606,548, Example 2

  However, the zoom lens described in Patent Document 3 is disadvantageous in reducing the thickness in the retracted state because the entire length of the zoom lens is long and the thickness of each lens group is large. In addition, a sufficient focus drive range by moving the third lens group at the telephoto end cannot be secured.

  In the zoom lenses described in Patent Document 1, Patent Document 2, and Patent Document 4, the second and third lens groups are moved together during zooming, and the third lens group is moved only during focusing. However, both have a long overall lens length and a large thickness of each lens group, which is disadvantageous for thinning.

  The present invention has been made in view of such problems of 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 an object of the present invention to provide a three-group zoom lens that can be secured, which is advantageous for ensuring miniaturization and optical performance, and an imaging apparatus using the same.

The present invention is, in order from the object side, a three-group zoom lens including a first lens unit having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
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. Moves only to the object side when zooming
The second lens group includes at least three of a positive lens, a negative lens, and a positive lens in order from the object side.
Each lens consists of one cemented lens joined on the optical axis.
The third lens group is composed of one positive lens,
A three-group zoom lens satisfying the following conditional expressions (1) and (2):
_{1.0 <C jmax / f t <} 2.0 ··· (1)
4.0 <C _j (w) / _fw <6.0 (2)
Where C _{jmax is} the maximum value of the distance from the entrance surface of the first lens unit to the image plane in the zooming range from the wide-angle end to the telephoto end,
f _t : focal length at the telephoto end of the three-group zoom lens,
C _j (w): distance from the entrance surface of the first lens unit to the image surface at the wide-angle end,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

Hereinafter, a zoom lens constituting the modification and the background of the present invention will be described.

The three-group zoom lens of this configuration is a three-group zoom lens 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 in order from the object side. ,
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. Moves only to the object side when zooming
The second lens group is composed of one cemented lens in which at least three lenses of a positive lens, a negative lens, and a positive lens are cemented on the optical axis in order from the object side,
The third lens group is composed of one positive lens.

Hereinafter, the reason and operation of the zoom lens having this configuration will be described.

The above-described configuration is common, and is a three-group zoom lens including, in order from the object side, a first lens unit having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. ,
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. And the third lens unit is composed of a single positive lens. That is, the third lens group is configured to move to the object side when zooming to the telephoto side.

  With this configuration, the height of the light beam of the third lens group can be made lower than when the third lens group is fixed or moved to the image side during zooming. Therefore, the diameter of the third lens group can be reduced.

  In particular, since the third lens group is a single positive lens, the minimum configuration is simple, which is advantageous for downsizing when retracted.

  The second lens group is composed of one cemented lens in which at least three lenses of a positive lens, a negative lens, and a positive lens are cemented on the optical axis in order from the object side.

  With this configuration, the second lens group includes three lenses that easily suppress the occurrence of aberrations in the second lens group, and the second lens group includes one cemented lens. The air space inside is omitted, and the second lens group itself is advantageously reduced in size and secured in the movement range of the third lens group.

  In order to achieve a reduction in thickness when the zoom lens is retracted, it is effective to reduce the thickness of the lens barrel member as well as the lens group as much as possible. As described above, since the configuration of the second lens group is only a cemented lens, it is only necessary to hold at least one of the lenses in the second lens group, and the thickness of the frame can be reduced. It is advantageous for thinning when retracted.

  It is more preferable to reduce the weight of the third lens group by using a plastic single lens.

  Further, focusing is preferably performed by moving only the third lens group.

In this configuration , the third lens unit moves toward the object side as the telephoto side. In this case, the focus sensitivity in the third lens group becomes high, and the power of the third lens group can be relaxed. Therefore, the thickness of the third lens group can be reduced, which is advantageous for reducing the thickness when the lens barrel is retracted.

  Further, when the third lens group is a focus group, the third lens group is only one lens, and the weight of the lens can be suppressed, so that the drive system can be simplified and the lens frame can be made smaller. Contribute.

  The focus sensitivity of the third lens group depends on the magnification of the third lens group. Therefore, it is preferable to satisfy the following conditional expression so that the focus sensitivity of the third lens unit at the telephoto end is appropriately increased.

0.5 <1-β _3T ² <1.0 (B)
Where β _3T : lateral magnification at the telephoto end of the third lens group,
It is.

  If the upper limit of 1.0 of the conditional expression (B) is exceeded, the lateral magnification in the third lens group increases in the negative direction and the distance to the image plane increases, so the effect of downsizing is reduced. If the lower limit of 0.5 is not reached, the amount of movement of the third lens group increases, the space for the focusing operation increases, and the effect of downsizing the entire zoom lens during use decreases.

  In addition, it is preferable that the first lens group includes a negative lens and a positive lens in order from the object side.

  With this configuration, it is possible to easily balance aberration such as chromatic aberration while reducing the size of the first lens unit closer to the object and in use. Further, it is effective for both maintaining optical performance and making the lens frame thinner when retracted.

Another three-group zoom lens having this configuration includes, in order from the object side, a first lens group having a negative refractive power,
A three-group zoom lens comprising a second lens group having positive refracting power and a third lens group having positive refracting power;
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. Moves only to the object side when zooming
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 includes three lenses including a positive lens and a negative lens,
The third lens group includes one positive lens,
The following conditional expression (1) is satisfied.

_{1.0 <C jmax / f t <} 2.0 ··· (1)
Where C _{jmax is} the maximum value of the distance from the entrance surface of the first lens unit to the image plane in the zooming range from the wide-angle end to the telephoto end,
f _t : focal length at the telephoto end of the three-group zoom lens,
It is.

  When the first lens group has the above-described configuration, it is easy to achieve a balance between miniaturization and securing of aberration performance.

  By configuring the second lens group as described above, a balance between thinning and optical performance can be preferably configured. Further, it is advantageous for securing a moving space for the third lens group.

  Conditional expression (1) defines the maximum lens total length with respect to the focal length at the telephoto end of the zoom lens, and is a condition for improving the balance between thinning of the lens frame and aberration correction.

  If the lower limit of 1.0 of the conditional expression (1) is exceeded, the power of each group becomes strong, and aberrations such as off-axis aberration in the first lens group and on-axis aberration in the second lens group on the wide angle side. It becomes difficult to correct in a balanced manner. Or the influence on the aberration by a manufacturing error becomes large, and the adjustment at the time of an assembly becomes difficult.

  If the upper limit of 2.0 of conditional expression (1) is exceeded, the total length of the zoom lens becomes long, and therefore the total length of the lens frame becomes short. Therefore, in order to make the lens frame thinner, it is necessary to increase the number of collapsible steps, leading to a complicated lens frame mechanism and an increase in diameter. Or, it becomes difficult to obtain a desired zoom ratio.

  Moreover, it is preferable that the following conditional expression (2) is satisfied.

4.0 <C _j (w) / f _w <6.0 (2)
Where C _j (w): the distance from the entrance surface of the first lens group to the image plane at the wide-angle end,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

  Conditional expression (2) defines the total length of the zoom lens at the wide-angle end with respect to the focal length at the wide-angle end of the zoom lens, and is a condition for facilitating both miniaturization and ensuring a zoom ratio. If the lower limit of 4.0 to condition (2) is not exceeded, it will be easy to suppress an increase in the total length in the telephoto end state. Or it becomes easy to obtain a desired zoom ratio. If the upper limit of 6.0 of the conditional expression (2) is not exceeded, it is possible to prevent the light ray height in the first lens group from increasing and to prevent the front lens diameter from increasing. Alternatively, it is possible to suppress an increase in the total length of the zoom lens and to suppress an increase in the number of retracted steps of the lens frame.

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

−0.005 <(D ₂ (t) −D ₂ (w)) / f _w <0.5 (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 _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

  Conditional expression (3) defines the difference between the second and third lens groups at the telephoto end and the wide-angle end in terms of the focal length at the wide-angle end, and achieves both ease of image position correction and downsizing. It is a condition for. If the lower limit of -0.005 of conditional expression (3) is not exceeded, it will be easy to secure the interval necessary for adjusting the image plane position deviation by adjusting the position of the third lens group. In addition, when focusing is performed with the third lens group, it is easy to secure an interval necessary for focusing at the telephoto end. If the upper limit of 0.5 of the conditional expression (3) is not exceeded, the light ray height of the first lens group at the wide-angle end is suppressed from increasing, and the increase in the front lens diameter is easily suppressed. Alternatively, it is possible to suppress an increase in the off-axis ray height of the third lens group that is the final lens at the telephoto end, which is advantageous in reducing the lens diameter.

  In addition, when the holding frame that holds the third lens group is held upright from the holding frame of the second lens group, the length of the axis becomes longer according to the amount of movement of the third lens group. Therefore, by satisfying conditional expression (3), it is possible to easily reduce the thickness when retracted.

  In addition, it is preferable that the second lens group includes a single cemented lens including three lenses of a positive lens, a negative lens, and a positive lens in order from the object side.

  According to the description of the first zoom lens described above, the second lens can be configured in this way while the three lenses of positive, negative, and positive lenses that can easily suppress the occurrence of aberrations in the second lens group. By configuring the group with a single cemented lens, the second lens group itself can be downsized and the moving range of the third lens group can be secured.

  Alternatively, it is preferable that the second lens group includes a single lens positive lens and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side.

  By adopting such a configuration, the lens arrangement is such that the principal point is the object side, which is advantageous in reducing the size of the front lens and securing the zoom ratio.

Still another three-group zoom lens of this configuration is a three-group zoom 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 in order from the object side. A lens,
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. Moves only to the object side when zooming
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 includes three lenses including a positive lens and a negative lens,
The third lens group includes one positive lens,
The following conditional expressions (4) and (5) are satisfied.

1.2 <| Δ _2g / f _w | <2.0 (4)
0.4 <Σd _2g / f _w <0.74 (5)
Where Δ _2g is the amount of movement of the second lens unit during zooming from the wide-angle end to the telephoto end,
Σd _2g : thickness of the second lens group on the optical axis,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

  As described above, by specifying the number of each lens group, it is possible to achieve a good balance between miniaturization, imaging performance, securing a zoom ratio, and the like.

  Conditional expression (4) defines the amount of movement of the second lens unit in zooming at the wide-angle end focal length, and balances securing an appropriate zooming ratio, miniaturization, adjustment of the exit pupil, and the like. Is the condition.

  When the lower limit of 1.2 of the conditional expression (4) is exceeded, it becomes difficult to obtain a desired zoom ratio. When the upper limit of 2.0 is exceeded, it becomes difficult to make the entire length compact at the telephoto end. In addition, the variation of the exit pupil position is likely to be large, and it becomes difficult to ensure good shading characteristics over the entire zoom range.

  Conditional expression (5) defines the thickness of the second lens group on the optical axis in terms of the focal length at the wide-angle end, and is a condition for balancing downsizing and the influence of assembly errors.

  If the lower limit of 0.4 of the conditional expression (5) is exceeded, it will be susceptible to eccentricity during assembly and processing tolerances, making it difficult to ensure stable quality. If the upper limit of 0.74 is exceeded, the thickness of the second lens group increases, which is disadvantageous for thinning the lens barrel when retracted.

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

−0.005 <(D ₂ (t) −D ₂ (w)) / f _w <0.5 (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,
It is.

  Since the operation of the conditional expression (3) has been described above, it will be omitted.

  In addition, it is preferable that the second lens group includes a single cemented lens including a positive lens, a negative lens, and a positive lens in order from the object side.

  Since this operation has been described above, it will be omitted.

  Alternatively, it is preferable that the second lens group includes a single lens positive lens and a cemented lens in which a positive lens and a negative lens are cemented in order from the object side.

  Since this operation has been described above, it will be omitted.

  Moreover, it is preferable that the following conditional expression (6) is satisfied.

1.3 <C _j (t) / _ft <1.8 (6)
Where C _j (t): distance from the entrance surface of the first lens group to the image plane at the telephoto end,
f _t : focal length at the telephoto end of the three-group zoom lens,
It is.

  Conditional expression (6) defines the total length of the zoom lens at the telephoto end by the focal length at the telephoto end, and is a condition for enabling the configuration of the lens barrel to be simplified by shortening the total length.

  If the lower limit of 1.3 of conditional expression (6) is not exceeded, an increase in the total length in the wide-angle end state can be easily suppressed. Alternatively, it is easy to obtain a desired zoom ratio. If the upper limit of 1.8 of conditional expression (6) is not exceeded, the entire length of the lens frame can be easily suppressed, which is advantageous for downsizing.

  In addition, it is preferable that the third lens unit moves for focusing and satisfies the following conditional expression (7).

3.0 <f ₃ / f _w <10 (7)
Where f _{3 is} the focal length of the third lens group,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

  Conditional expression (7) defines the focal length of the third lens group in terms of the focal length at the wide-angle end of the zoom lens. In the present invention, the third lens unit is advantageously reduced in size by the moving method of the third lens unit. In particular, when the third lens group is a focus lens group, the burden on the driving mechanism can be reduced compared to other focusing methods. However, in the present invention, the focus sensitivity of the third lens group at the telephoto end is large. The refractive power of the third lens group can be made reasonably small so as to satisfy the conditional expression (7), which is advantageous for further downsizing.

  If the lower limit of 3.0 of conditional expression (7) is not exceeded, it is easy to suppress the light beam height at the first lens group at the wide-angle end, and it becomes easy to reduce the front lens diameter (the diameter of the first lens group). . Alternatively, an increase in the thickness of the third lens group is suppressed, which is advantageous for reducing the thickness of the lens frame. If the upper limit of 10 in the conditional expression (7) is not exceeded, the amount of movement of the third lens unit during focusing is suppressed, which is advantageous for thinning.

  Moreover, 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 at the telephoto end of the three-group zoom lens,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is.

  This conditional expression (A) defines the zoom ratio of the zoom lens. In the present invention, it is preferable to use a three-unit zoom lens having an appropriate zoom ratio of 2.5 or more because the size of the entire system and the optical performance are easily balanced.

  If the lower limit of 2.5 of the 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.

  In addition, it is preferable to have a configuration including an aperture stop that is disposed immediately before the second lens group and moves integrally with the second lens group at the time of zooming.

  With such a 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. Also, the movement mechanism of the aperture stop can be shared with the second lens group, and the configuration can be simplified easily.

  In addition, it is preferable that the imaging apparatus includes any one of the above-described three-group zoom lenses and an imaging element that is arranged on the image side and converts an optical image into an electric signal.

  The zoom lens of the present invention is advantageous in reducing the size and securing the angle of view at the wide-angle end, and is easy to have a substantially telecentric configuration. Therefore, the incident angle of the light beam on the imaging surface can be suppressed, and the influence of color shading can be reduced. Therefore, it is preferable to use the imaging device having the above-described imaging element.

  Each of the above-described configurations 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 structural requirement described dependent on a specific structure 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 more favorable, it is preferable to adopt the following configuration for each conditional expression.
For conditional expression (1), it is more preferable to set the lower limit value to 1.3, and further to 1.5, in order to make the balance between the thinning of the lens frame and aberration correction better.

  Further, it is more preferable that the upper limit value is 1.95, more preferably 1.9.

  For conditional expression (2), it is more preferable to set the lower limit value to 4.3, and further to 4.5, in order to achieve better compatibility between miniaturization and securing of a zoom ratio.

  Further, it is more preferable that the upper limit value is 5.8, and further 5.7.

  For conditional expression (3), it is more preferable to set the lower limit value to -0.04, and further to -0.03, in order to improve the compatibility between ease of image position correction and downsizing.

  Further, the upper limit value is more preferably 0.47, and further preferably 0.46.

  In conditional expression (4), it is more preferable to set the lower limit value to 1.3, and further to 1.35, in order to achieve a better balance of securing the zoom ratio, miniaturization, and adjustment of the exit pupil.

  Further, it is more preferable that the upper limit value is 1.9, and further 1.8.

  For conditional expression (5), it is more preferable to set the lower limit value to 0.45, more preferably 0.5, in order to make the balance between miniaturization and the influence of assembly errors better.

  Regarding conditional expression (6), in order to make the balance of the total length better, the lower limit value is preferably 1.4, and more preferably 1.5.

  Further, it is more preferable that the upper limit value is 1.76.

  Regarding conditional expression (7), in order to balance the reduction in the diameter of the third lens unit and the reduction in the overall length, it is more preferable that the lower limit value is 3.5, and further 4.0.

  It is more preferable that the upper limit value is 9.0.

  In the conditional expression (A), it is more preferable to set the lower limit value to 2.6, and further to 2.7, in order to improve the balance between miniaturization and securing the zoom ratio.

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

  For conditional expression (B), it is more preferable to set the lower limit value to 0.5 and further to 0.7 in order to improve the balance between ensuring focus sensitivity and miniaturization.

  Further, it is more preferable that the upper limit value is 0.97.

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

Hereinafter, Examples 1 to 8 of the third group zoom lens will be described. In Examples 2 and 6, the configuration of the second lens group is a positive lens, a positive lens, and a negative lens in order from the object side, and is described as a reference example. FIGS. 1 to 8 show lens cross-sectional views of 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 8, 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 ( CCD and CMO
The parallel plate of the cover glass of S) is indicated by C, and the image plane (light receiving surface of the electronic image sensor) is indicated by I. Note that a multilayer film for limiting the wavelength band may be applied to the surface of the cover glass G. Further, the cover glass G may have a low-pass filter function.

  As shown in FIG. 1, the zoom optical system according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a first lens group having a positive refractive power. The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end from the position of the wide-angle end. Located on the image 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 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. 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 third lens group G3 includes one biconvex positive 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 the image side surface of the negative 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 the biconvex shape of the third lens group G3. The positive lens is used for four surfaces on the object side.

  As shown in FIG. 2, the zoom optical system 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 first lens group having a positive refractive power. Consists of three lens groups G3, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves with a concave locus on the object side, and at the telephoto end, the object is slightly more intermediate than in the intermediate state. It is located on the image side from the wide-angle end position. 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 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 includes a biconvex positive lens, The third lens group G3 is composed of a single biconvex positive lens. The positive lens is a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The aperture stop S is located at the same position as the object side surface of the biconvex positive lens of the second lens group G2.

  The aspherical surfaces are used on the three surfaces of the negative meniscus lens image side surface of the first lens group G1 and both surfaces of the biconvex positive lens of the second lens group G2.

  As shown in FIG. 3, the zoom optical system 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 first lens group having a positive refractive power. Consists of three lens groups G3, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves with a concave locus on the object side, and at the telephoto end, the object is slightly more intermediate than in the intermediate state. It is located on the image side from the wide-angle end position. 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 to the object side while once increasing the distance from the second lens group G2 and then 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. 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 third lens group G3 includes one biconvex positive 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 surface is the image side surface of the negative meniscus lens of the first lens group G1, the object side surface of the positive meniscus lens of the first lens group G1, and the most object side surface of the three-piece cemented lens of the second lens group G2. And 6 surfaces of the image side surface and both surfaces of the biconvex positive lens of the third lens group G3.

  As shown in FIG. 4, the zoom optical system according to the fourth 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 first lens group having a positive refractive power. Consists of three lens groups G3, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves with a concave locus on the object side, and at the telephoto end, the object is slightly more intermediate than in the intermediate state. It is located on the image side from the wide-angle end position. 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 to the object side while once increasing the distance from the second lens group G2 and then 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, 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 meniscus 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. 5, the zoom optical system according to the fifth 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 first lens group having a positive refractive power. The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end from the position of the wide-angle end. Located on the image 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 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. 6, the zoom optical system according to the sixth 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 first lens group having a positive refractive power. The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end from the position of the wide-angle end. Located on the image 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 positive 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 at the same position as 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, on both surfaces of the biconvex positive lens of the second lens group G2, and on the image side surface of the biconvex positive lens of the third lens group G3. Used on the surface.

  As shown in FIG. 7, the zoom optical system 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 first lens group having a positive refractive power. The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end from the position of the wide-angle end. Located on the image 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 to the object side while once increasing the distance from the second lens group G2 and then 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 includes a biconvex positive lens and both lenses. The third lens group G3 is composed of one positive meniscus lens having a convex surface facing the object side. The third lens group G3 is composed of a cemented lens composed of a concave negative lens and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is located at the same position as the object side surface of the biconvex positive lens of the second lens group G2.

  The aspherical surfaces are the image side surface of the negative 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 the positive meniscus of the third lens group G3. It is used on the 5 sides of the lens.

  As shown in FIG. 8, the zoom optical system according to the eighth embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a first lens group having a positive refractive power. The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end from the position of the wide-angle end. Located slightly on the image 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 reducing 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 includes a biconvex positive lens and both lenses. The third lens group G3 is composed of one positive meniscus lens having a convex surface facing the object side. The third lens group G3 is composed of a cemented lens composed of a concave negative lens and a positive meniscus lens having a convex surface facing the object side. The aperture stop S is located at the same position as the object side surface of the biconvex positive lens of the second lens group G2.

  The aspheric surfaces are the image side surface of the positive meniscus 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 meniscus of the third lens group G3. It is used on the 5 sides of the lens.

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
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A ₄ , A ₆ , A ₈ , and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.

Example 1
r ₁ = 50.852 d ₁ = 0.90 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 5.799 (aspherical surface) d ₂ = 1.89
r ₃ = 9.201 d ₃ = 1.76 n _d2 = 2.00069 ν _d2 = 25.46
r ₄ = 16.258 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.60
r ₆ = 5.636 (aspherical surface) d ₆ = 2.63 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = 11.974 d ₇ = 1.71 n _d4 = 1.80518 ν _d4 = 25.42
r ₈ = 4.090 d ₈ = 1.25 n _d5 = 1.58313 ν _d5 = 59.38
r ₉ = 13.539 (aspherical surface) d ₉ = (variable)
r ₁₀ = 18.182 (aspherical surface) d ₁₀ = 1.50 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₁ = -61.937 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 = 0.47
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -1.118
A ₄ = 4.40772 × 10 ^-4
A ₆ = -1.79165 × 10 ^-7
A ₈ = 6.84992 × 10 ^-8
A ₁₀ = -4.27115 × 10 ^-10
6th surface K = -0.831
A ₄ = 5.53954 × 10 ^-4
A ₆ = -6.08508 × 10 ^-7
A ₈ = 1.25836 × 10 ^-6
A ₁₀ = -3.07335 × 10 ^-8
Surface 9 K = 0.000
A ₄ = 1.86701 × 10 ^-3
A ₆ = 9.48986 × 10 ^-5
A ₈ = -1.36654 × 10 ^-7
A ₁₀ = 1.56679 × 10 ^-6
10th surface K = 0.000
A ₄ = -7.43754 × 10 ^-5
A ₆ = 7.82756 × 10 ^-6
A ₈ = 0
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 7.90 15.23 22.84
F _NO 2.97 3.93 4.95
2ω (°) 62.52 33.69 22.70
d ₄ 16.00 4.96 1.00
d ₉ 3.47 3.89 5.15
d ₁₁ 7.21 12.48 17.95.

Example 2
r ₁ = 60.375 d ₁ = 0.90 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 5.749 (aspherical surface) d ₂ = 2.08
r ₃ = 9.939 d ₃ = 2.00 n _d2 = 2.00069 ν _d2 = 25.46
r ₄ = 19.633 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.00
r ₆ = 6.733 (aspherical surface) d ₆ = 2.00 n _d3 = 1.58913 ν _d3 = 61.28
r ₇ = -20.821 (aspherical surface) d ₇ = 0.10
r ₈ = 5.168 d ₈ = 1.70 n _d4 = 1.49700 ν _d4 = 81.54
r ₉ = 7.903 d ₉ = 0.50 n _d5 = 2.00069 ν _d5 = 25.46
r ₁₀ = 3.793 d ₁₀ = (variable)
r ₁₁ = 21.078 d ₁₁ = 1.70 n _d6 = 1.52542 ν _d6 = 55.78
r ₁₂ = -42.921 d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.86 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 = 0.50
r ₁₇ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.352
A ₄ = -1.27821 × 10 ^-4
A ₆ = 3.81118 × 10 ^-7
A ₈ = -1.53718 × 10 ^-7
A ₁₀ = -3.01038 × 10 ^-10
6th surface K = -0.663
A ₄ = -2.82950 × 10 ^-4
A ₆ = -1.04899 × 10 ^-6
A ₈ = -1.26909 × 10 ^-6
A ₁₀ = 0
Surface 7 K = -0.563
A ₄ = -3.61449 × 10 ^-5
A ₆ = -1.05788 × 10 ^-5
A ₈ = -5.36698 × 10 ^-7
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 7.00 11.86 20.20
F _NO 2.85 3.51 4.61
2ω (°) 69.04 42.45 25.50
d ₄ 16.80 6.71 0.50
d ₁₀ 4.51 5.26 6.05
d ₁₂ 4.54 7.56 13.36.

Example 3
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 = 0.42
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 4.47 7.38 12.10.

Example 4
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 5
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 6
r ₁ = -253.431 d ₁ = 1.00 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 6.524 (aspherical surface) d ₂ = 1.57
r ₃ = 9.882 d ₃ = 2.00 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 24.764 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = 0.00
r ₆ = 7.186 (aspherical surface) d ₆ = 2.00 n _d3 = 1.69350 ν _d3 = 53.20
r ₇ = -62.824 (aspherical surface) d ₇ = 0.10
r ₈ = 7.116 d ₈ = 1.50 n _d4 = 1.88300 ν _d4 = 40.76
r ₉ = 7.772 d ₉ = 0.60 n _d5 = 1.92286 ν _d5 = 18.90
r ₁₀ = 4.109 d ₁₀ = (variable)
r ₁₁ = 19.941 d ₁₁ = 1.70 n _d6 = 1.58913 ν _d6 = 61.14
r ₁₂ = -37.021 (aspherical surface) d ₁₂ = (variable)
r ₁₃ = ∞ d ₁₃ = 0.86 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 = 0.50
r ₁₇ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.403
A ₄ = -5.30123 × 10 ^-5
A ₆ = 1.55843 × 10 ^-6
A ₈ = -8.23618 × 10 ^-8
A ₁₀ = 3.83367 × 10 ^-10
6th surface K = -0.552
A ₄ = -1.95147 × 10 ^-4
A ₆ = -8.83262 × 10 ^-6
A ₈ = -4.39594 × 10 ^-7
A ₁₀ = 0
Surface 7 K = -117.722
A ₄ = -1.76410 × 10 ^-4
A ₆ = -7.63343 × 10 ^-6
A ₈ = -4.35389 × 10 ^-7
A ₁₀ = 0
Surface 12 K = -7.421
A ₄ = 5.77763 × 10 ^-6
A ₆ = -2.75734 × 10 ^-6
A ₈ = 0
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 7.18 11.15 20.67
F _NO 2.85 3.40 4.62
2ω (°) 72.33 46.25 25.25
d ₄ 15.64 7.63 0.50
d ₁₀ 3.90 5.02 7.17
d ₁₂ 6.17 8.63 15.59.

Example 7
r ₁ = 157.020 d ₁ = 1.00 n _d1 = 1.80610 ν _d1 = 40.92
r ₂ = 4.547 (aspherical surface) d ₂ = 1.05
r ₃ = 6.272 d ₃ = 2.20 n _d2 = 1.80810 ν _d2 = 22.76
r ₄ = 13.255 d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.45
r ₆ = 3.721 (aspherical surface) d ₆ = 1.40 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = -7358.609 d ₇ = 0.50 n _d4 = 1.68893 ν _d4 = 31.07
r ₈ = 3.002 d ₈ = 1.19 n _d5 = 1.51633 ν _d5 = 64.14
r ₉ = 6.657 (aspherical surface) d ₉ = (variable)
r ₁₀ = 11.922 (aspherical surface) d ₁₀ = 1.10 n _d6 = 1.52511 ν _d6 = 56.23
r ₁₁ = 30423.657 (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 = 0.49
r ₁₆ = ∞ (image plane)
Aspheric coefficient 2nd surface K = -0.273
A ₄ = -4.57253 × 10 ^-5
A ₆ = -8.76429 × 10 ^-6
A ₈ = 2.14403 × 10 ^-8
A ₁₀ = -2.20356 × 10 ^-8
6th surface K = -0.978
A ₄ = 2.62235 × 10 ^-3
A ₆ = 5.71552 × 10 ^-5
A ₈ = 1.38662 × 10 ^-5
A ₁₀ = -7.25720 × 10 ^-8
Surface 9 K = 0.000
A ₄ = 7.42985 × 10 ^-3
A ₆ = 6.75400 × 10 ^-4
A ₈ = 1.92625 × 10 ^-4
A ₁₀ = 1.93182 × 10 ^-5
10th surface K = 0.000
A ₄ = 5.04258 × 10 ^-4
A ₆ = 2.09830 × 10 ^-4
A ₈ = 1.45376 × 10 ^-5
A ₁₀ = 2.75747 × 10 ^-6
11th surface K = 0.000
A ₄ = 4.21538 × 10 ^-4
A ₆ = 1.53746 × 10 ^-4
A ₈ = 4.60241 × 10 ^-6
A ₁₀ = 4.35430 × 10 ^-6
Zoom data (∞)
WE ST TE
f (mm) 5.96 9.94 17.14
F _NO 3.41 4.28 5.79
2ω (°) 72.71 43.42 25.23
d ₄ 10.66 4.78 0.95
d ₉ 2.66 3.12 3.06
d ₁₁ 5.40 8.27 13.96.

Example 8
r ₁ = 212.622 d ₁ = 0.80 n _d1 = 1.69350 ν _d1 = 53.21
r ₂ = 5.061 d ₂ = 1.84
r ₃ = 9.120 d ₃ = 1.50 n _d2 = 1.84666 ν _d2 = 23.78
r ₄ = 14.258 (aspherical surface) d ₄ = (variable)
r ₅ = ∞ (aperture) d ₅ = -0.50
r ₆ = 4.470 (aspherical surface) d ₆ = 2.32 n _d3 = 1.74320 ν _d3 = 49.34
r ₇ = -22.186 d ₇ = 0.80 n _d4 = 1.71736 ν _d4 = 29.52
r ₈ = 4.101 d ₈ = 1.37 n _d5 = 1.51633 ν _d5 = 64.14
r ₉ = 14.762 (aspherical surface) d ₉ = (variable)
r ₁₀ = 10.675 (aspherical surface) d ₁₀ = 1.21 n _d6 = 1.58393 ν _d6 = 30.21
r ₁₁ = 16.123 (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 = 0.60
r ₁₆ = ∞ (image plane)
Aspheric coefficient 4th surface K = 0.000
A ₄ = -2.93212 × 10 ^-4
A ₆ = -8.62541 × 10 ^-6
A ₈ = -2.81496 × 10 ^-7
A ₁₀ = 0
6th surface K = -0.964
A ₄ = 1.16351 × 10 ^-3
A ₆ = 4.17698 × 10 ^-5
A ₈ = 6.21747 × 10 ^-7
A ₁₀ = 0
Surface 9 K = 0.000
A ₄ = 4.34772 × 10 ^-3
A ₆ = 3.69556 × 10 ^-4
A ₈ = 4.92494 × 10 ^-5
A ₁₀ = 0
10th surface K = 0.000
A ₄ = -1.12133 × 10 ^-3
A ₆ = 5.83908 × 10 ^-5
A ₈ = 0
A ₁₀ = 0
11th surface K = 0.000
A ₄ = -9.59381 × 10 ^-4
A ₆ = 2.73144 × 10 ^-5
A ₈ = 0
A ₁₀ = 0
Zoom data (∞)
WE ST TE
f (mm) 6.31 12.16 18.24
F _NO 3.21 4.42 5.69
2ω (°) 69.52 35.50 23.64
d ₄ 10.22 3.36 0.90
d ₉ 3.29 3.27 3.25
d ₁₁ 4.06 8.62 13.42.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 8 are shown in FIGS. In these aberration diagrams, (a) shows the spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) at the wide-angle end, and (b) at the telephoto end. In each figure, “FIY” indicates the maximum image height.

  Next, parameter values relating to the angle of view and the conditional expressions (1) to (7), (A), and (B) in the above-described embodiments will be described.

Example 1 2 3 4 5 6 7 8
(1) 1.74 1.94 1.85 1.73 1.76 1.87 1.67 1.59
(2) 5.02 5.60 5.36 4.99 5.08 5.37 4.82 4.59
(3) 0.21 0.22 0.00 0.10 0.04 0.45 0.07 -0.01
(4) 1.57 1.48 1.38 1.37 1.44 1.77 1.50 1.48
(5) 0.71 0.61 0.69 0.56 0.73 0.59 0.52 0.71
(6) 1.62 1.65 1.62 1.52 1.60 1.75 1.63 1.59
(7) 3.41 3.88 6.09 4.54 6.29 3.10 3.80 7.92
(A) 2.89 2.88 2.90 2.89 2.88 2.88 2.88 2.89
(B) 0.94 0.83 0.66 0.79 0.65 0.97 0.92 0.56.

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

For example, as shown in FIG. 17, 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. 17, 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) = 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.

  18 to 20 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. 18 is a front perspective view showing the external appearance of the digital camera 40, FIG. 19 is a rear front view thereof, and FIG. 20 is a schematic cross-sectional view showing the configuration of the digital camera 40. However, in FIGS. 18 and 20, 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. 20, 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. 21 is a block diagram showing the internal circuitry of the main part of the digital camera 40. In the following description, the processing unit 51 includes, for example, the CDS / ADC unit 24, the 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. 21, 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. 3 is a lens cross-sectional view at the wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the third group zoom lens of the present invention. FIG. 6 is a view similar to FIG. 1 of Embodiment 2 of the three-group zoom lens of the present invention. FIG. 6 is a view similar to FIG. 1 of Embodiment 3 of the three-group zoom lens of the present invention. FIG. 6 is a view similar to FIG. 1 of Embodiment 4 of the three-group zoom lens of the present invention. FIG. 6 is a view similar to FIG. 1 of Embodiment 5 of the three-group zoom lens of the present invention. FIG. 6 is a view similar to FIG. 1 of Example 6 of the three-group zoom lens of the present invention. FIG. 10 is a view similar to FIG. 1 of Embodiment 7 of the three-group zoom lens of the present invention. FIG. 9 is a view similar to FIG. 1 of Embodiment 8 of the three-group 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. 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. 19 is a rear perspective view of the digital camera of FIG. 18. It is sectional drawing of the digital camera of FIG. FIG. 19 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 18.

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 (10)

A three-group zoom lens comprising, 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,
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. Moves only to the object side when zooming
The second lens group is composed of one cemented lens in which at least three lenses of a positive lens, a negative lens, and a positive lens are cemented on the optical axis in order from the object side,
The third lens group is composed of one positive lens,
A three-group zoom lens satisfying the following conditional expressions (1) and (2):
_{1.0 <C jmax / f t <} 2.0 ··· (1)
4.0 <C _j (w) / _fw <6.0 (2)
Where C _{jmax is} the maximum value of the distance from the entrance surface of the first lens unit to the image plane in the zooming range from the wide-angle end to the telephoto end,
f _t : focal length at the telephoto end of the three-group zoom lens,
C _j (w): distance from the entrance surface of the first lens unit to the image surface at the wide-angle end,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is. 2. The three-group zoom lens according to claim 1, wherein only the third lens group moves during focusing. 3. The three-group zoom lens according to claim 2, wherein the following conditional expression (B) is satisfied.
0.5 <1-β _3T ² <1.0 (B)
Where β _3T : lateral magnification at the telephoto end of the third lens group,
It is. 4. The three-group zoom lens according to claim 1, wherein the first lens group includes two lenses of a negative lens and a positive lens in order from the object side. 5. The three-group zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied.
_{-0.005 <(D 2 (t)} -D 2 (w)) / f w <0.5 ··· (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 _w : Focal length at the wide-angle end of the three-group zoom lens,
It is. 6. The three-group zoom lens according to claim 1, wherein the following conditional expression (6) is satisfied.
1.3 <C _j (t) / _ft <1.8 (6)
Where C _j (t): distance from the entrance surface of the first lens group to the image plane at the telephoto end,
f _t : focal length at the telephoto end of the three-group zoom lens,
It is. 7. The three-unit zoom lens according to claim 1, wherein the third lens unit moves for focusing and satisfies the following conditional expression (7): 7.
3.0 <f ₃ / _fw <10 (7)
Where f _{3 is} the focal length of the third lens group,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is. The three-unit zoom lens according to claim 1, wherein the following condition is satisfied.
2.5 ≦ f _t / f _w <5.5 (A)
Where f _t : focal length at the telephoto end of the three-group zoom lens,
f _w : Focal length at the wide-angle end of the three-group zoom lens,
It is. 9. 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. 10. 3 group zoom lens. 10. An image pickup comprising: the third group zoom lens according to claim 1; and an image pickup device that is disposed on an image side of the third group zoom lens and converts an optical image into an electric signal. apparatus.

Images