JP2006301154A - Zoom lens and electronic imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high variable power zoom lens that has a magnification of three times or more while having a sufficient wide angle area and a compact configuration. <P>SOLUTION: The zoom lens includes, in order from the object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power, changes distances between the lens groups to vary a magnification, and satisfies four conditional equations (1) to (4); (1) 0.80<IH/f<SB>w</SB><1.5, (2) 2.7<f<SB>t</SB>/f<SB>w</SB><12, (3) 0.05<¾d<SB>a</SB>/f<SB>1G</SB>¾<10, and (4) 0<d<SB>b</SB>/f<SB>2G</SB><3, where IH is photographing image height of the zoom lens, f<SB>w</SB>is the focal length at the wide angle end of the total system of the zoom lens, f<SB>t</SB>is the focal length at the telephoto end of the total system of the zoom lens, f<SB>1G</SB>is the focal length of the first lens group, f<SB>2G</SB>is the focal length of the second lengs group, and d<SB>a</SB>is the on-axis interval between the first lens group and the second lens group when the total system of the zoom lens has any focal length f<SB>ra</SB>satisfying the condition (a) of IH/0.92<f<SB>ra</SB><IH/0.8, wherein d<SB>b</SB>is the on-axis internal between the first lens group and the second lens group when the total system of the zoom lens group has any focal length f<SB>rb</SB>satisfying the condition (b) of 2.7<f<SB>rb</SB>/f<SB>ra</SB><5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a zoom lens and an electronic imaging device using the same, and more particularly to a zoom lens and an electronic imaging device including a wide field angle region.

  There is a growing demand for a zoom lens that has high imaging performance applicable to a so-called lens-integrated digital camera and that includes a wide field angle region. Further, these zoom lenses are expected not only to have a wide shooting range, but also to expand the flexibility of changing the shooting range in combination with a so-called digital zoom function for enlarging a part of a shot image. However, in the case of digital zoom, since a part of the photographed image is enlarged, the image quality is deteriorated more than the photographing lens performance and the imaging device performance. Therefore, a zoom lens having a certain zoom ratio is desired.

  So far, a zoom lens or the like that is compact, has a zoom magnification exceeding 3 times, and includes a wide angle of view has not been proposed.

As proposals so far, there are zoom lenses for photographing with a zoom magnification exceeding 3 times and a comparatively wide angle of view, such as Patent Document 1 and Patent Document 2, but further widening is desired. Yes.
JP 2004-191599 A JP 2001-42218 A JP 2004-4533 A JP 2004-564343 A

  The present invention has been made in view of such a situation of the prior art, and an object thereof is to provide a zoom lens having a sufficiently wide angle range and a high zoom ratio and an imaging device using the same. .

  Furthermore, an object of the present invention is to provide a zoom lens and an electronic imaging device for taking a picture using an electronic imaging device, which is a zoom lens having a zoom ratio of 3 times or more while having a compact configuration. .

  The first zoom lens of the present invention that achieves the above object has, 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, The zoom lens system is characterized in that the following conditional expressions (1) to (4) are satisfied by changing the interval between the lens units during zooming.

0.80 <IH / f _w <1.5 (1)
2.7 < _ft / _fw <12 (2)
0.05 <| d _a / f _1G | <10 (3)
0 <d _b / f _2G <3 (4)
Where IH is the image height of the zoom lens,
f _w is the focal length at the wide-angle end of the entire zoom lens system,
f _t is the focal length at the telephoto end of the entire zoom lens system,
f _1G is the focal length of the first lens group,
f _2G is the focal length of the second lens group,
d _a is the axial distance between the first lens group and the second lens group when the entire zoom lens system has any focal length f _ra that satisfies the following condition (a):
IH / 0.92 <f _ra <IH / 0.8 (a)
d _b is the axial distance between the first lens group and the second lens group when the entire zoom lens system has any focal length _fr that satisfies the following condition (b):
2.7 <f _rb / f _ra <5 (b)
It is.

  Hereinafter, the reason and action of the above configuration in the first zoom lens of the present invention will be described.

  In order from the object side, a negative first lens group and a positive second lens group disposed on the image side of the first lens group with a variable interval in between are incident at a large angle of view. The light beam is refracted with a negative refracting power and guided to the second lens group having a positive refracting power.

  Therefore, by satisfying conditional expression (1), it is possible to reduce the outer diameter of the first lens group while maintaining a wide shooting angle of view due to the focal length at the wide-angle end. By reducing the outer diameter of the first lens group, it is advantageous to make the configuration length of the first lens group compact and to increase the power of the first lens group.

  In the present invention, the positive third lens group is further arranged on the image plane side of the positive second lens group, so that the image plane of the luminous flux is satisfied while satisfying the zoom ratio defined by the conditional expression (2). It is possible to reduce the change in the incident angle to the.

  In particular, when an electronic image sensor that converts an optical image into an electrical signal is arranged on the image side of the zoom lens, the zoom lens of the present invention can ensure telecentricity, so that light is incident on the image sensor at an angle. It is possible to reduce the adverse effects caused by doing.

  If the lower limit of 0.80 of conditional expression (1) is exceeded, the shooting range becomes narrow, and the shooting range cannot be covered even by image processing or the like. On the other hand, if the upper limit of 1.5 of the conditional expression (1) is exceeded, the refractive power of the entire optical system becomes too strong, and if an attempt is made to secure a zoom ratio that satisfies the conditional expression (2), It becomes difficult to correct aberrations in groups.

  If the upper limit of 12 in conditional expression (2) is exceeded, the burden of refracting power sharing on the negative first lens group will increase, making it difficult to ensure compactness while correcting aberration fluctuations. Exceeding the lower limit of 2.7 of the conditional expression (2) is not preferable because the degree of deterioration in image quality when shooting a distant subject is greatly increased with respect to the improvement in compactness.

  If the upper limit of conditional expression (2) is exceeded, the amount of movement of the second lens group tends to be large, and the compactness is impaired.

Conditional expression (3) defines the power in the first lens group at the interval between the first and second lens groups at an arbitrary focal length _fra defined by expression (a).

  If the lower limit of 0.05 of conditional expression (3) is exceeded, the power of the first lens group becomes too weak and the total length when the telephoto end is used becomes long. On the other hand, if the upper limit of 10 in the conditional expression (3) is exceeded, the distance between the first lens group and the second lens group becomes too large, which is contrary to compactness.

Conditional expression (4) defines the power in the second lens group at the interval between the first and second lens groups at an arbitrary focal length _frb in which the zoom ratio defined in expression (b) is ensured.

  If the lower limit of 0 in the conditional expression (4) is exceeded, the first lens group and the second lens group interfere with each other. Exceeding the upper limit of 3 to conditional expression (4) complicates the configuration after the second lens group, such as an increase in the power of the second lens group.

  For conditional expression (1), it is more preferable that the photographing range is made wider and the lower limit value is 0.85, further 0.87.

  In order to make it easier to reduce the aberration in each group, it is more preferable that the upper limit value is 1.3, and further 1.1.

  Regarding conditional expression (2), in order to improve the image quality at the time of distant view shooting, it is more preferable to set the lower limit value to 3.5, and further to 4.0.

  In order to make it more compact, it is more preferable that the upper limit value is 7.0, and even 6.0.

  For conditional expression (3), it is more preferable to set the lower limit to 1.0, and further to 2.0 in order to reduce the overall length.

  More preferably, the upper limit value is 7.0, more preferably 5.0.

  Regarding conditional expression (4), if the upper limit value is 1.0, and further 0.2, it is more preferable because the configuration after the second lens group can be further simplified.

  In addition, in order to reduce the light emission angle of the entire zoom lens system and to facilitate aberration correction of the entire system while suppressing the increase in the outer diameter of the first lens group, it is easier to correct the aberration than the first lens group. It is preferable to provide an aperture stop (aperture stop) closer to the object side than the lens closest to the image side of the second lens group on the surface side.

In addition, further, f _ra = f _w, may be as f _rb = f _t.

  In that case, conditional expression (1) is replaced by conditional expression (a), and conditional expression (2) is replaced by conditional expression (b).

  The second zoom lens of the present invention is characterized in that, in the first zoom lens, the following conditional expression (5) is satisfied.

−0.07 <IH / r ₁ <0.07 (5)
Here, r ₁ is the paraxial radius of curvature of the most object side lens surface in the first lens group.

  The third zoom lens according to the present invention is characterized in that, in the second zoom lens, the following conditional expression (5 ′) is satisfied instead of conditional expression (5).

−0.015 <IH / r ₁ <0.04 (5 ′)
Hereinafter, the reason and operation of the second and third zoom lenses according to the present invention will be described.

  Increasing the paraxial radius of curvature of the lens surface (first surface) closest to the object in the first lens group can make the entrance pupil position shallower, so that the lens outer diameter can be reduced. In addition, the difference in angle formed between each light beam constituting the incident light beam off the axis and the first surface is reduced, which is advantageous for correction of coma aberration. In addition, the imaging range can be widened while maintaining the imaging performance. Further, the first surface having a large change in the axial beam diameter has a small curvature near the optical axis, so that the change in spherical aberration due to zooming can be reduced, and the aberration correction burden on the second lens group can be reduced, which is preferable.

  If the lower limit of -0.07 in conditional expression (5) is exceeded, the incident angle of the off-axis light beam becomes large on the first surface, and it becomes difficult to maintain the imaging performance. When the upper limit of 0.07 is exceeded, the entrance pupil position becomes shallow, the outer diameter of the lens becomes large and the compactness is impaired, and the lens configuration of the first lens group must be complicated in order to secure the angle of view. Or, it is disadvantageous for correction of coma aberration. Therefore, the configuration of the entire lens system becomes complicated, which is not preferable. Alternatively, the field angle must be reduced and the shooting range must be reduced.

  In conditional expression (5), it is more preferable that the lower limit value be −0.015, more preferably 0.0.

  Alternatively, the upper limit value is more preferably 0.04, and further preferably 0.033.

  For example, it is more preferable to reduce both the upper and lower limits of the conditional expression (5) to obtain the conditional expression (5 ′). This is advantageous by reducing the outer diameter of the lens, maintaining the imaging performance, and ensuring a wide imaging range.

  Further, when the lens component closest to the object side in the first lens group has a concave surface on the image side, it is possible to prevent the radius of curvature of the concave surface from becoming too small, and to correct spherical aberration and coma aberration well. .

  In the fourth zoom lens of the present invention, in the first to third zoom lenses, at the time of zooming from the wide angle end to the telephoto end, the first lens group moves, and the second lens group moves toward the object side. And an aperture stop that moves together with the second lens group upon zooming.

  Hereinafter, the reason and action of the above-described configuration in the fourth zoom lens of the present invention will be described.

  By moving the aperture stop together with the second lens group that performs zooming, the change in the range of the incident light beam to the second lens group can be reduced. Therefore, it is possible to suppress fluctuations in aberrations associated with the movement of the second lens group.

  More preferably, by moving the first lens group to the image side after zooming from the wide-angle end to the telephoto end and then moving to the object side, a compact zoom lens including a lens barrel structure can be obtained.

  According to a fifth zoom lens of the present invention, in the fourth zoom lens, the aperture stop is disposed between the first lens group and the second lens group.

  The reason and action of the fifth zoom lens according to the present invention will be described below.

  With such a configuration, the entrance pupil can be made shallow, and the outer diameter of the first lens group can be reduced. In addition, the influence of the decentering of the lens element due to the manufacturing error in the second lens group can be easily reduced, and the lens frame structure and the lens configuration can be easily simplified.

  According to a sixth zoom lens of the present invention, in the first to fifth zoom lenses, the zoom lens includes, in order from the object side, a lens group having refractive power, the first lens group having negative refractive power, and the positive lens group. The zoom lens is a three-unit zoom lens including a second lens unit having refractive power and a third lens unit having positive refractive power.

  The reason and action of the sixth zoom lens according to the present invention will be described below.

  With such a configuration, a retrofocus system that is advantageous for a wide-angle lens system with a small number of groups as a whole can be achieved, and exit pupil control suitable for an electronic imaging device can be performed.

  More preferably, moving the third lens group at the time of zooming is more advantageous for controlling the exit pupil.

  According to a seventh zoom lens of the present invention, in the first to sixth zoom lenses, the most object side lens L11 of the first lens group is a negative meniscus lens having a convex surface facing the object side. To do.

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

  With such a configuration, it is easy to suppress excessive generation of negative distortion while increasing the angle of view at the wide-angle end.

  According to an eighth zoom lens of the present invention, in the first to seventh zoom lenses, the first lens group is disposed on the image side of the negative lens with an air space on the axis between the negative lens and the axis from the object side. And a negative meniscus lens having a convex surface facing the object side.

  Hereinafter, the reason and action of the above configuration in the eighth zoom lens of the present invention will be described.

  With such a configuration, off-axis rays can be gradually bent, so that occurrence of off-axis aberrations can be suppressed.

  According to a ninth zoom lens of the present invention, in the first to eighth zoom lenses, the first lens group includes a negative lens having an aspherical surface.

  The reason and operation of the ninth zoom lens according to the present invention will be described below.

  With such a configuration, the lens can be made small by efficiently correcting off-axis aberrations such as field curvature.

  According to a tenth zoom lens of the present invention, in the first to ninth zoom lenses, the first lens group is arranged on the image side of the negative lens with an air space on the axis from the negative lens to the object side. The negative lens disposed on the image side has an aspherical surface.

  The reason and action of the above-described configuration in the tenth zoom lens of the present invention will be described below.

  The negative lens on the image side has a smaller outer diameter than the negative lens on the object side, and is advantageous for using an aspherical surface in terms of manufacturing cost. Further, by providing an aspherical surface for this negative lens, an effect can be obtained in terms of balance with correction of other aberrations.

  According to an eleventh zoom lens of the present invention, in the tenth zoom lens, the negative lens arranged on the image side has two aspheric surfaces.

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

  With such a configuration, the effect of an aspheric surface can be gradually given to the off-axis light beam, which is preferable in terms of aberration correction. In addition, since one lens has a plurality of aspheric surfaces, the number of lenses having aspheric surfaces can be reduced. This can be advantageous in terms of manufacturing such as manufacturing cost. Specifically, it is more preferable in terms of manufacturing cost if only the negative lens arranged on the image side among the lenses in the first lens group is an aspherical lens.

  In a twelfth zoom lens according to the present invention, in the first to eleventh zoom lenses, the first lens group includes three lens elements of a negative lens L11, a negative lens L12, and a positive lens L13 in order from the object side. It is characterized by.

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

  With such a configuration, off-axis rays can be gradually bent by the two negative lenses L11 and L12, so that occurrence of off-axis aberrations can be suppressed. Furthermore, chromatic aberration can be corrected by disposing the positive lens L13 on the image plane side. By using two negative lenses L11 and L12 and one positive lens L13 in the entire first lens group, the principal point can be arranged on the object side, and the outer diameter of the lens can be made compact.

  According to a thirteenth zoom lens of the present invention, in the first to twelfth zoom lenses, the third lens group is composed of one positive lens.

  The reason and action of the above-described configuration in the thirteenth zoom lens of the present invention will be described below.

  If the zooming and aberration correction are mainly performed by the first lens group and the second lens group, and the third lens group is a single positive lens, a reduction in thickness can be realized.

  According to a fourteenth zoom lens of the present invention, in the first to thirteenth zoom lenses, the third lens group includes one positive lens having at least one aspheric surface.

  The reason and action of the above configuration in the fourteenth zoom lens of the present invention will be described below.

  By providing an aspheric surface, it is easy to achieve both correction of off-axis aberrations and ensuring telecentricity, and the third lens group can be made thinner.

  According to a fifteenth zoom lens of the present invention, in the first to fourteenth zoom lenses, the second lens group includes a positive lens component, a negative lens component, and a positive lens component in order from the object side. Is. However, the lens component is a lens in which the object side surface and the image side surface are in contact with air and there is no space between these surfaces, that is, a single lens or a cemented lens.

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

  By adopting such a configuration, it is possible to suppress aberration fluctuations accompanying the movement of the group. That is, it is desirable that the second lens group can be charged with a main magnification change, and the configuration of the entire optical system can be simplified.

  According to a sixteenth zoom lens of the present invention, in the first to fifteenth zoom lenses, the second lens group has a positive lens component closest to the object side, and the positive lens component satisfies the following conditional expression: It is characterized by this.

−8 <(r ₂₁ + r ₂₂ ) / (r ₂₁ −r ₂₂ ) <0 (6)
However, the lens component is a lens in which the object side surface and the image side surface are in contact with air and there is no space between those surfaces, that is, a single lens or a cemented lens,
r ₂₁ is the paraxial radius of curvature of the object side surface of the positive lens component,
r ₂₂ is the paraxial radius of curvature of the image side surface of the positive lens component,
It is.

  The seventeenth zoom lens according to the present invention is characterized in that, in the sixteenth zoom lens, the following conditional expression (6 ′) is satisfied instead of conditional expression (6).

−2 <(r ₂₁ + r ₂₂ ) / (r ₂₁ −r ₂₂ ) <− 0.5 (6 ′)
Hereinafter, the reason and action of the above-described configuration in the 16th and 17th zoom lenses of the present invention will be described.

  In the second lens group, by arranging a positive lens having a strong convex surface on the object side closest to the object side, the main point of the second lens group is closer to the object side, and high zooming is easily achieved. In particular, as described above (the twelfth zoom lens or the like), in order to make the outer diameter of the first lens group compact, this configuration is used when the principal point of the first lens group is arranged on the object side. Is valid.

  If the lower limit −8 of conditional expression (6) is exceeded, the power of the lens becomes weak, and as a result, it becomes difficult to simplify the configuration of the second lens group. When the upper limit of 0 to conditional expression (6) is exceeded, the effect of disposing the principal point on the object side becomes small.

  In conditional expression (6), it is more preferable to set the lower limit to −2 and further to −1.5 in order to secure the power of the lens component.

  Alternatively, it is more preferable to set the upper limit value to −0.5, and further to −0.8 in order to easily secure the zoom ratio.

  For example, it is more preferable to reduce both the upper and lower limits of the conditional expression (6) to obtain the conditional expression (6 ′).

  According to an eighteenth zoom lens of the present invention, in the first to seventeenth zoom lenses, a lens surface closest to the object side of the second lens group is an aspherical surface.

  The reason and action of the above configuration in the 18th zoom lens of the present invention will be described below.

  With this configuration, the aberration of the axial light beam can be corrected well. In particular, when the aperture stop is disposed on the object side of the second lens group, the effect is enhanced. Further, the most object side lens of the second lens group may be a positive lens convex on the object side. It is easy to reduce the lens diameter of the second lens group by converging the axial light beam incident on the second lens group. If this convex surface has a strong power, it is advantageous for making the diameter of the second lens group small, but spherical aberration is also likely to occur. Therefore, it is possible to correct spherical aberration by making this surface an aspherical surface. it can.

  According to a nineteenth zoom lens of the present invention, in the fifteenth to eighteenth zoom lenses, the second lens group includes, in order from the object side, a single lens having a positive refractive power, a cemented lens of a positive lens and a negative lens, and positive refraction. It is composed of a single lens of force.

  The reason and action of the above-described configuration in the nineteenth zoom lens of the present invention will be described below.

  By incorporating positive and negative cemented lenses, it is possible to suppress the deterioration of performance due to the relative eccentricity of the negative lens with respect to the positive lens. In addition, the power arrangement is substantially symmetrical within the second lens group, which is advantageous for correcting the aberration of the second lens group itself, and that two positive lenses are arranged on the object side, so that the main point of the second lens group is Can be configured closer to the object, which is advantageous for securing a zoom ratio that satisfies the condition (2).

  The electronic imaging device of the present invention is an electronic imaging device including a zoom lens and an electronic imaging device that is disposed on the image side and converts an optical image into an electrical signal. The zoom lens is any one of the above.

  Below, the reason and effect | action which take the said structure in the electronic imaging device of this invention are demonstrated.

  It is preferable to provide an electronic imaging device in which an electronic imaging device that converts an optical image into an electric signal is disposed on the image side of any zoom lens of the present invention.

  In the zoom lens of the present invention, since telecentricity can be ensured, adverse effects caused by oblique incidence of light rays on the image sensor can be reduced. In that case, the captured image height IH of the zoom lens means half of the diagonal length of the effective imaging region on the electronic image sensor. The effective imaging area means the maximum range of the imaging area used for displaying, printing, and the like for the received image in the photoelectric conversion surface of the electronic imaging device.

  In the present invention described above, distortion aberration correction by image processing as proposed in Patent Document 3 and Patent Document 4 may be performed. Patent Documents 3 to 4 also report that distortion correction is easier than coma aberration and spherical aberration in aberration correction by image processing. Of course, image processing may be performed with equipment other than the photographed camera equipment after photographing.

  Further, any one of the following conditional expressions (7) to (11) may be satisfied individually or plurally.

IH / HB ₁ <0.5 (7)
0.2 <IH / HB ₁ <0.5 (7 ′)
However, HB ₁ is the distance from the top of the image side lens surface to the rear principal point of the first lens group, and the object side direction is positive.

  If the upper limit of 0.5 in conditional expressions (7) and (7 ′) is exceeded, the rear principal point position of the first lens group (distance from the top of the image side lens surface of the first lens group to the rear principal point) Becomes shorter, and the height of the light incident on the first lens becomes higher. As a result, it is disadvantageous for reducing the diameter of the first lens. If the lower limit of 0.2 of the conditional expression (7 ') is exceeded and the principal point position of the first lens group is too close to the object side, the power of the first lens group becomes too strong and it becomes difficult to correct aberrations.

  In the conditional expression (7 ′), it is more preferable that the lower limit value is 0.3, further 0.35.

  In the conditional expression (7) or (7 ′), it is more preferable that the upper limit value is 0.47, and further 0.45.

Also,
3.2 <f _2G / f _w (8)
3.2 <f _2G / f _w <5.5 (8 ′)
Where f _2G is the focal length of the second lens group,
It is.

  If the lower limit of 3.2 to conditional expression (8) is exceeded, the power of the second lens group becomes too strong, making it difficult to suppress aberration fluctuations associated with group movement for zooming.

  It is further preferable that an upper limit value is set in the conditional expression (8) to satisfy the conditional expression (8 ′).

  If the upper limit of 5.5 of the conditional expression (8 ′) is exceeded, the power of the second lens group that mainly performs zooming becomes weak, the zooming function is lowered, and as a result, it is difficult to realize a high zooming ratio. .

  In the conditional expression (8 ′), it is more preferable that the lower limit value is 3.3, further 3.5.

  In the conditional expression (8 ′), it is more preferable that the upper limit value is 5.0, more preferably 4.0.

Also,
IH / HD _12w <0.13 (9)
HD _12w is the distance from the rear principal point of the first lens group to the front principal point of the second lens group at the wide angle end, and the image side direction is positive.

  If the upper limit of 0.13 of conditional expression (9) is exceeded, the distance between the principal points of the first and second lens groups will be shortened. Therefore, it becomes difficult to further reduce the distance between the principal points of the first lens group and the second lens group at the telephoto end, and it becomes difficult to obtain a high zoom ratio.

  In conditional expression (9), it is more preferable that the upper limit value is 0.12, and further 0.11.

Also,
TL _w / f _w > 13.5 (10)
Where TL _w is the axial distance from the entrance surface of the zoom lens to the image plane at the wide-angle end,
It is.

  If the lower limit of 13.5 of conditional expression (10) is exceeded, it will be difficult to sufficiently correct aberrations while maintaining a wide angle of view.

  In conditional expression (10), it is more preferable to set the lower limit to 14.0, more preferably 15.0.

  In addition, it is preferable to set an upper limit value in conditional expression (10) and make it smaller than 25.0 to shorten the entire length of the zoom lens at the wide angle end.

Also,
2.0 <| f _1G / f _w | <3.5 (11)
If the upper limit of 3.5 of the conditional expression (11) is exceeded and the focal length of the first lens unit becomes long, the total lens length at the wide angle end becomes long, which is disadvantageous for miniaturization. If the lower limit of 2.0 is exceeded and the focal length of the first lens group becomes short, the magnification of the second lens group at the telephoto end becomes too large, and performance degradation due to manufacturing errors tends to increase.

  In conditional expression (11), it is more preferable to set the lower limit to 2.4, and even 2.7.

  In the conditional expression (11), it is more preferable that the upper limit value is 3.4, more preferably 3.3.

  Each of the above-described configurations and conditional expressions are more effective because the respective effects are obtained by appropriately combining them.

  According to the present invention described above, it is possible to obtain a zoom lens having a high zoom ratio and an electronic image pickup apparatus using the zoom lens while having a sufficiently wide angle region and being advantageous for downsizing.

  Examples 1 to 4 of the zoom lens according to the present invention will be described below. 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 4 are shown in FIGS. 1 to 4, the first lens group is G1, the aperture stop is S, the second lens group is G2, the third lens group is G3, and a low-pass filter with a wavelength band limiting coat that limits infrared light is configured. The parallel plate of the cover glass of the electronic image sensor such as F, CCD, or CMOS is indicated by C, and the image plane is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action.

  As shown in FIG. 1, the zoom lens according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. The first lens group G1 moves along a concave locus toward the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is configured. The aperture stop S and the second lens group G2 are monotonously moved to the object side integrally, and the third lens group G3 is moved to the image plane side.

  In order from the object side, the first lens group G1 includes two negative meniscus lenses 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. It consists of a lens, a cemented lens 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 biconvex positive lens. The third lens group G3 has one biconvex positive lens. Consists of.

  The aspherical surfaces are both surfaces of the second negative meniscus lens from the object side of the first lens group G1, the object side surface of the biconvex positive lens on the object side of the second lens group G2, and the biconvex positive of the third lens group G3. It is used on the 5 sides of the lens.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. The first lens group G1 moves along a concave locus toward the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is configured. The aperture stop S and the second lens group G2 are monotonously moved toward the object side integrally, and the third lens group G3 is moved from the wide-angle end to the intermediate state toward the image plane side. It is substantially fixed from the intermediate state to the telephoto end.

  In order from the object side, the first lens group G1 includes two negative meniscus lenses 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. It consists of a lens, a cemented lens 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 biconvex positive lens. The third lens group G3 has one biconvex positive lens. Consists of.

  The aspherical surfaces are both surfaces of the second negative meniscus lens from the object side of the first lens group G1, the object side surface of the biconvex positive lens on the object side of the second lens group G2, and the biconvex positive of the third lens group G3. It is used on the 5 sides of the lens.

  As shown in FIG. 3, the zoom lens of Embodiment 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. The first lens group G1 moves along a concave locus toward the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is configured. The aperture stop S and the second lens group G2 are monotonously moved to the object side integrally, and the third lens group G3 is moved to the image plane side.

  In order from the object side, the first lens group G1 is composed of two negative meniscus lenses 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 is disposed on the object side. A positive meniscus lens having a convex surface, a cemented lens 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 biconvex positive lens. The third lens group G3 includes: It consists of one biconvex positive lens.

  The aspheric surfaces are the surfaces of the second negative meniscus lens from the object side of the first lens group G1, the object side surface of the positive meniscus lens of the second lens group G2, and both surfaces of the biconvex positive lens of the third lens group G3. Used on 5 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 positive refraction. The first lens group G1 moves along a concave locus toward the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end, the wide-angle end is configured. The aperture stop S and the second lens group G2 are monotonously moved to the object side integrally, and the third lens group G3 is moved to the image plane side.

  In order from the object side, the first lens group G1 includes two negative meniscus lenses 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. It consists of a lens, a cemented lens 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 biconvex positive lens. The third lens group G3 has one biconvex positive lens. Consists of.

  The aspherical surfaces are both surfaces of the second negative meniscus lens from the object side of the first lens group G1, the object side surface of the biconvex positive lens on the object side of the second lens group G2, and the biconvex positive of the third lens group G3. It is used on the 5 sides of the lens.

  For each of the zoom lenses described above, the short distance focusing may be performed by moving the entire lens or a specific lens group. Further, it is preferable to move only the third lens group, since the change in magnification is suppressed and fewer lenses are moved.

  The range of the actual field angle 2ω from the wide-angle end to the telephoto end in the first to fourth embodiments is as follows.

Example 1 Actual angle of view 2ω 91.7 ° to 21.8 °
Example 2 Actual angle of view 2ω 91.7 ° to 21.7 °
Example 3 Actual angle of view 2ω 91.6 ° to 22.3 °
Example 4 Actual angle of view 2ω 82.9 ° to 21.9 °.

In the following, the numerical data of each of the above embodiments is shown. Symbols are the above, f is the total focal length, _FNO is the F number, WE is the wide angle end, ST is the intermediate state, TE is the telephoto end, r ₁ , r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1, n _d2 ... d-line refractive index of each lens, ν _d1, ν _d2 ... each It is the Abbe number of the 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 aspherical coefficients, respectively.

Example 1
r ₁ = 120.490 d ₁ = 1.31 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 8.803 d ₂ = 2.41
r ₃ = 18.045 (aspherical surface) d ₃ = 1.43 n _d2 = 1.74330 ν _d2 = 49.33
r ₄ = 8.094 (aspherical surface) d ₄ = 3.05
r ₅ = 14.990 d ₅ = 2.92 n _d3 = 1.84666 ν _d3 = 23.78
r ₆ = 40.520 d ₆ = (variable)
r ₇ = ∞ (aperture) d ₇ = 0.50
r ₈ = 14.360 (aspherical surface) d ₈ = 1.96 n _d4 = 1.74330 ν _d4 = 49.33
r ₉ = -331.278 d ₉ = 0.37
r ₁₀ = 12.927 d ₁₀ = 3.50 n _d5 = 1.77250 ν _d5 = 49.60
r ₁₁ = 115.263 d ₁₁ = 2.37 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₂ = 7.486 d ₁₂ = 0.69
r ₁₃ = 33.417 d ₁₃ = 1.95 n _d7 = 1.48749 ν _d7 = 70.23
r ₁₄ = -13.786 d ₁₄ = (variable)
r ₁₅ = 21.995 (aspherical surface) d ₁₅ = 2.97 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -21.106 (aspherical surface) d ₁₆ = (variable)
r ₁₇ = ∞ d ₁₇ = 0.76 n _d9 = 1.54771 ν _d9 = 62.84
r ₁₈ = ∞ d ₁₈ = 0.44
r ₁₉ = ∞ d ₁₉ = 0.40 n _d10 = 1.51633 ν _d10 = 64.14
r ₂₀ = ∞ d ₂₀ = 0.60
r ₂₁ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -2.076
A ₄ = 6.45927 × 10 ^-5
A ₆ = 6.49359 × 10 ^-6
A ₈ = -8.75295 × 10 ^-8
A ₁₀ = 3.45632 × 10 ^-10
4th surface K = -0.123
A ₄ = -2.45406 × 10 ^-4
A ₆ = 6.68743 × 10 ^-6
A ₈ = -1.43236 × 10 ^-7
A ₁₀ = -2.58394 × 10 ^-10
Surface 8 K = -2.842
A ₄ = 5.45802 × 10 ^-5
A ₆ = -8.40498 × 10 ^-7
A ₈ = 3.93728 × 10 ^-8
A ₁₀ = -8.90443 × 10 ^-10
Surface 15 K = 17.207
A ₄ = -4.08931 × 10 ^-4
A ₆ = 3.36877 × 10 ^-5
A ₈ = -1.34835 × 10 ^-6
A ₁₀ = 1.83688 × 10 ^-8
16th surface K = -5.667
A ₄ = -2.68421 × 10 ^-4
A ₆ = 8.59656 × 10 ^-5
A ₈ = -4.00016 × 10 ^-6
A ₁₀ = 9.20195 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 3.991 8.545 18.189
F _NO 2.80 3.67 4.80
d ₆ 26.79 9.98 2.08
d ₁₄ 5.33 12.90 28.33
d ₁₆ 2.41 2.20 1.98.

Example 2
r ₁ = 118.807 d ₁ = 1.31 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 8.809 d ₂ = 2.41
r ₃ = 18.035 (aspherical surface) d ₃ = 1.39 n _d2 = 1.74330 ν _d2 = 49.33
r ₄ = 7.941 (aspherical surface) d ₄ = 3.10
r ₅ = 15.161 d ₅ = 3.00 n _d3 = 1.84666 ν _d3 = 23.78
r ₆ = 44.116 d ₆ = (variable)
r ₇ = ∞ (aperture) d ₇ = 0.50
r ₈ = 12.553 (aspherical surface) d ₈ = 2.00 n _d4 = 1.74330 ν _d4 = 49.33
r ₉ = -1072.915 d ₉ = 0.47
r ₁₀ = 14.652 d ₁₀ = 2.88 n _d5 = 1.77250 ν _d5 = 49.60
r ₁₁ = 116.690 d ₁₁ = 2.58 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₂ = 7.579 d ₁₂ = 0.66
r ₁₃ = 28.801 d ₁₃ = 1.98 n _d7 = 1.48749 ν _d7 = 70.23
r ₁₄ = -13.779 d ₁₄ = (variable)
r ₁₅ = 25.196 (aspherical surface) d ₁₅ = 3.23 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -20.772 (aspherical surface) d ₁₆ = (variable)
r ₁₇ = ∞ d ₁₇ = 0.76 n _d9 = 1.54771 ν _d9 = 62.84
r ₁₈ = ∞ d ₁₈ = 0.44
r ₁₉ = ∞ d ₁₉ = 0.40 n _d10 = 1.51633 ν _d10 = 64.14
r ₂₀ = ∞ d ₂₀ = 0.60
r ₂₁ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -2.753
A ₄ = 5.55177 × 10 ^-5
A ₆ = 6.78542 × 10 ^-6
A ₈ = -8.75312 × 10 ^-8
A ₁₀ = 3.00839 × 10 ^-10
4th surface K = -0.154
A ₄ = -2.78544 × 10 ^-4
A ₆ = 7.01729 × 10 ^-6
A ₈ = -1.42051 × 10 ^-7
A ₁₀ = -3.59350 × 10 ^-10
Surface 8 K = -2.029
A ₄ = 4.38908 × 10 ^-5
A ₆ = -2.45433 × 10 ^-7
A ₈ = -8.67387 × 10 ^-9
A ₁₀ = 4.57999 × 10 ^-10
Surface 15 K = 26.077
A ₄ = -4.19155 × 10 ^-4
A ₆ = 3.06327 × 10 ^-5
A ₈ = -1.13473 × 10 ^-6
A ₁₀ = 3.54518 × 10 ^-9
16th surface K = -3.248
A ₄ = -2.66612 × 10 ^-4
A ₆ = 8.09076 × 10 ^-5
A ₈ = -3.64091 × 10 ^-6
A ₁₀ = 7.64667 × 10 ^-8
Zoom data (∞)
WE ST TE
f (mm) 3.990 8.545 18.288
F _NO 2.80 3.67 4.80
d ₆ 26.74 9.60 1.50
d ₁₄ 5.18 12.57 28.03
d ₁₆ 2.52 2.40 2.40.

Example 3
r ₁ = 4500.383 d ₁ = 1.32 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 9.359 d ₂ = 2.41
r ₃ = 24.524 (aspherical surface) d ₃ = 1.39 n _d2 = 1.74330 ν _d2 = 49.33
r ₄ = 8.963 (aspherical surface) d ₄ = 2.41
r ₅ = 17.943 d ₅ = 2.89 n _d3 = 1.84666 ν _d3 = 23.78
r ₆ = 284.297 d ₆ = (variable)
r ₇ = ∞ (aperture) d ₇ = 0.50
r ₈ = 19.436 (aspherical surface) d ₈ = 1.53 n _d4 = 1.74330 ν _d4 = 49.33
r ₉ = 137.997 d ₉ = 0.18
r ₁₀ = 11.381 d ₁₀ = 3.19 n _d5 = 1.77250 ν _d5 = 49.60
r ₁₁ = 4390.531 d ₁₁ = 3.25 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₂ = 8.260 d ₁₂ = 0.69
r ₁₃ = 26.872 d ₁₃ = 2.09 n _d7 = 1.48749 ν _d7 = 70.23
r ₁₄ = -12.935 d ₁₄ = (variable)
r ₁₅ = 24.500 (aspherical surface) d ₁₅ = 1.90 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -24.796 (aspherical surface) d ₁₆ = (variable)
r ₁₇ = ∞ d ₁₇ = 0.76 n _d9 = 1.54771 ν _d9 = 62.84
r ₁₈ = ∞ d ₁₈ = 0.44
r ₁₉ = ∞ d ₁₉ = 0.40 n _d10 = 1.51633 ν _d10 = 64.14
r ₂₀ = ∞ d ₂₀ = 0.60
r ₂₁ = ∞ (image plane)
Aspheric coefficient 3rd surface K = 0.000
A ₄ = -1.09346 × 10 ^-22
A ₆ = 7.42289 × 10 ^-6
A ₈ = -8.34361 × 10 ^-8
A ₁₀ = 2.82193 × 10 ^-10
4th surface K = -0.145
A ₄ = -2.76977 × 10 ^-4
A ₆ = 8.02851 × 10 ^-6
A ₈ = -1.22644 × 10 ^-7
A ₁₀ = -8.03256 × 10 ^-13
Surface 8 K = -4.326
A ₄ = 3.58731 × 10 ^-6
A ₆ = 1.37882 × 10 ^-6
A ₈ = -1.18290 × 10 ^-7
A ₁₀ = 3.57210 × 10 ^-9
Surface 15 K = 27.818
A ₄ = -5.16300 × 10 ^-4
A ₆ = -6.63410 × 10 ^-7
A ₈ = -1.73194 × 10 ^-6
A ₁₀ = -5.52968 × 10 ^-10
16th surface K = 0.000
A ₄ = -2.87839 × 10 ^-4
A ₆ = 4.85820 × 10 ^-5
A ₈ = -5.34160 × 10 ^-6
A ₁₀ = 1.27186 × 10 ^-7
Zoom data (∞)
WE ST TE
f (mm) 3.995 8.550 17.995
F _NO 2.77 3.36 4.83
d ₆ 27.65 10.79 2.05
d ₁₄ 3.80 13.22 27.89
d ₁₆ 4.77 3.08 1.86.

Example 4
r ₁ = 121.056 d ₁ = 1.43 n _d1 = 1.77250 ν _d1 = 49.60
r ₂ = 9.380 d ₂ = 2.15
r ₃ = 16.015 (aspherical surface) d ₃ = 1.44 n _d2 = 1.74330 ν _d2 = 49.33
r ₄ = 8.193 (aspherical surface) d ₄ = 2.98
r ₅ = 16.120 d ₅ = 2.94 n _d3 = 1.84666 ν _d3 = 23.78
r ₆ = 45.014 d ₆ = (variable)
r ₇ = ∞ (aperture) d ₇ = 0.47
r ₈ = 14.773 (aspherical surface) d ₈ = 1.86 n _d4 = 1.74330 ν _d4 = 49.33
r ₉ = -994.295 d ₉ = 0.33
r ₁₀ = 13.147 d ₁₀ = 2.82 n _d5 = 1.77250 ν _d5 = 49.60
r ₁₁ = 72.079 d ₁₁ = 2.42 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₂ = 8.130 d ₁₂ = 0.66
r ₁₃ = 29.342 d ₁₃ = 1.71 n _d7 = 1.48749 ν _d7 = 70.23
r ₁₄ = -16.090 d ₁₄ = (variable)
r ₁₅ = 25.866 (aspherical surface) d ₁₅ = 2.62 n _d8 = 1.49700 ν _d8 = 81.54
r ₁₆ = -21.997 (aspherical surface) d ₁₆ = (variable)
r ₁₇ = ∞ d ₁₇ = 0.76 n _d9 = 1.54771 ν _d9 = 62.84
r ₁₈ = ∞ d ₁₈ = 0.44
r ₁₉ = ∞ d ₁₉ = 0.40 n _d10 = 1.51633 ν _d10 = 64.14
r ₂₀ = ∞ d ₂₀ = 0.60
r ₂₁ = ∞ (image plane)
Aspheric coefficient 3rd surface K = -8.593
A ₄ = -5.21721 × 10 ^-5
A ₆ = 1.35472 × 10 ^-5
A ₈ = -1.60073 × 10 ^-7
A ₁₀ = 8.18893 × 10 ^-10
4th surface K = -0.267
A ₄ = -5.36622 × 10 ^-4
A ₆ = 1.87785 × 10 ^-5
A ₈ = -2.34186 × 10 ^-7
A ₁₀ = 6.47476 × 10 ^-10
Surface 8 K = -2.764
A ₄ = 3.65365 × 10 ^-5
A ₆ = 1.70796 × 10 ^-6
A ₈ = -1.47291 × 10 ^-7
A ₁₀ = 4.47653 × 10 ^-9
15th surface K = 31.103
A ₄ = -5.88505 × 10 ^-4
A ₆ = 5.86985 × 10 ^-6
A ₈ = -6.62903 × 10 ^-7
A ₁₀ = 3.27987 × 10 ^-9
16th surface K = -3.969
A ₄ = -6.53373 × 10 ^-4
A ₆ = 9.42874 × 10 ^-5
A ₈ = -6.79301 × 10 ^-6
A ₁₀ = 1.91081 × 10 ^-7
Zoom data (∞)
WE ST TE
f (mm) 4.460 9.095 18.274
F _NO 2.80 3.67 4.80
d ₆ 26.31 10.64 2.46
d ₁₄ 5.71 13.58 26.94
d ₁₆ 3.41 2.53 2.23.

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 4 are shown in FIGS. In these aberration diagrams, (a) is a wide-angle end, (b) is an intermediate state, and (c) is spherical aberration, astigmatism, distortion, and lateral chromatic aberration at a telephoto end. In each figure, “FIY” indicates the maximum image height.

Then, the angle in the above embodiment, the value of the conditional expression (1) to (10), _{and, IH, f w, f t} , d a, d b, f ra, f ra / IH, f rb, The values of f _rb / f _ra , f _1G , f _2G , r ₁ , r ₂₁ , r ₂₂ , HB ₁ , HD _12w , and TL _w are shown.

Example 1 Example 2 Example 3 Example 4
Conditional expression (1) 0.902 0.902 0.901 0.807
Conditional expression (2) 4.558 4.583 4.504 4.097
Conditional expression (3) 2.315 2.301 2.169 2.035
Conditional expression (4) 0.145 0.104 0.135 0.167
Conditional expression (5) 0.0299 0.0303 0.0008 0.0297
Conditional expression (6) -0.917 -0.977 -1.328 -0.971
Conditional expression (7) 0.424 0.412 0.399 0.440
Conditional expression (8) 3.598 3.599 3.797 3.309
Conditional expression (9) 0.104 0.103 0.098 0.106
Conditional expression (10) 15.57 15.58 15.56 13.78
Conditional expression (11) 2.899 2.912 3.191 2.899
IH 3.60 3.60 3.60 3.60
f _w 3.991 3.990 3.995 4.460
f _t 18.189 18.288 17.995 18.274
d _a 26.79 26.74 27.65 26.31
d _b 2.08 1.50 2.05 2.46
f _ra (Select focal length at wide angle end) 3.991 3.990 3.995 4.460
f _ra / IH 1.109 1.108 1.110 1.239
f _rb (Select the focal length at the telephoto end) 18.189 18.288 17.995 18.274
f _rb / f _ra 4.557 4.583 4.504 4.097
f _1G -11.57 -11.62 -12.75 -12.93
f _2G 14.36 14.36 15.17 14.76
r ₁ 120.490 118.807 4500.383 121.056
r ₂₁ 14.36 12.553 19.436 14.773
r ₂₂ -331.278 -1072.915 137.997 -994.295
HB ₁ 8.49 8.73 9.02 8.18
HD _12w 34.68 35.08 36.92 34.06
TL _w 62.15 62.15 62.17 61.45
.

  9 to 11 are conceptual diagrams of the configuration of the digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 41. FIG. 9 is a front perspective view showing the appearance of the digital camera 40, FIG. 10 is a rear front view thereof, and FIG. 11 is a schematic cross-sectional view showing the configuration of the digital camera 40. However, FIGS. 9 and 11 show a state in which the photographing optical system 41 is not retracted. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter button 45, a flash 46, a liquid crystal display monitor 47, a focal length change button 61, When the photographing optical system 41 is retracted, including the setting change switch 62, the photographing optical system 41, the finder optical system 43, and the flash 46 are covered with the cover 60 by sliding the cover 60. When the cover 60 is opened and the camera 40 is set to the photographing state, the photographing optical system 41 is brought into the non-collapsed state of FIG. 11, 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 the low-pass filter F and the 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 two prisms, and includes a zoom optical system whose focal length changes in conjunction with the zoom lens of the photographing optical system 41. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the erecting prism 55 that is an image erecting member. Behind the erecting prism 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.

  In the digital camera 40 configured in this way, the imaging optical system 41 has a sufficiently wide angle range and a compact configuration according to the present invention. Therefore, high performance, small size, 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. 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. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 10 is a rear perspective view of the digital camera of FIG. 9. It is sectional drawing of the digital camera of FIG.

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 40 ... Digital camera 41 ... Shooting optical system 42 ... Optical path for photographing 43 ... finder optical system 44 ... optical path for finder 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 ... Viewfinder objective optical system 55 ... Erect prism 57 ... Field frame 59 ... Eyepiece optical system 60 ... Cover 61 ... Focal length change button 62 ... Setting change switch

Claims (20)

In order from the object side, there are a first lens unit with negative refracting power, a second lens group with positive refracting power, and a third lens group with positive refracting power. A zoom lens satisfying the expressions (1) to (4).
0.80 <IH / f _w <1.5 (1)
2.7 < _ft / _fw <12 (2)
0.05 <| d _a / f _1G | <10 (3)
0 <d _b / f _2G <3 (4)
Where IH is the image height of the zoom lens,
f _w is the focal length at the wide-angle end of the entire zoom lens system,
f _t is the focal length at the telephoto end of the entire zoom lens system,
f _1G is the focal length of the first lens group,
f _2G is the focal length of the second lens group,
d _a is the axial distance between the first lens group and the second lens group when the entire zoom lens system has any focal length f _ra that satisfies the following condition (a):
IH / 0.92 <f _ra <IH / 0.8 (a)
d _b is the axial distance between the first lens group and the second lens group when the entire zoom lens system has any focal length _fr that satisfies the following condition (b):
2.7 <f _rb / f _ra <5 (b)
It is. 2. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied.
−0.07 <IH / r ₁ <0.07 (5)
Where r ₁ is the paraxial radius of curvature of the most object side lens surface in the first lens group,
It is. 3. The zoom lens according to claim 2, wherein the following conditional expression (5 ′) is satisfied instead of conditional expression (5).
−0.015 <IH / r ₁ <0.04 (5 ′) 4. The zoom lens according to claim 1, wherein the first lens group moves, the second lens group moves toward the object side, and at the time of zooming from the wide-angle end to the telephoto end. A zoom lens comprising an aperture stop that moves together with the second lens group upon zooming. 5. The zoom lens according to claim 4, wherein the aperture stop is disposed between the first lens group and the second lens group. 6. 6. The zoom lens according to claim 1, wherein the zoom lens includes, in order from the object side, a lens group having refractive power, a first lens group having negative refractive power, and a lens group having positive refractive power. A zoom lens comprising a second lens group and a third lens group having a positive refractive power and a third lens group. 7. The zoom lens according to claim 1, wherein the most object side lens L <b> 11 of the first lens group is a negative meniscus lens having a convex surface directed toward the object side. 8. . 8. The zoom lens according to claim 1, wherein the first lens group is disposed on the image side of the negative lens with an air space on the axis between the negative lens and the axis from the object side. A zoom lens comprising a negative meniscus lens having a convex surface facing the surface. 9. The zoom lens according to claim 1, wherein the first lens group includes a negative lens having an aspherical surface. 10. 10. The zoom lens according to claim 1, wherein the first lens group is a negative lens disposed on the image side of the negative lens with an air space between the negative lens and the axis from the object side. And the negative lens disposed on the image side has an aspherical surface. The zoom lens according to claim 10, wherein the negative lens disposed on the image side has two aspheric surfaces. The zoom lens according to any one of claims 1 to 11, wherein the first lens group includes three lens elements in order from the object side: a negative lens L11, a negative lens L12, and a positive lens L13. A featured zoom lens. The zoom lens according to any one of claims 1 to 12, wherein the third lens group is composed of one positive lens. 14. The zoom lens according to claim 1, wherein the third lens group includes one positive lens having at least one aspheric surface. 15. The zoom lens according to claim 1, wherein the second lens group includes a positive lens component, a negative lens component, and a positive lens component in order from the object side. However, the lens component is a lens in which the object side surface and the image side surface are in contact with air and there is no space between these surfaces, that is, a single lens or a cemented lens. 16. The zoom lens according to claim 1, wherein the second lens group has a positive lens component closest to the object side, and the positive lens component satisfies the following conditional expression. Zoom lens.
−8 <(r ₂₁ + r ₂₂ ) / (r ₂₁ −r ₂₂ ) <0 (6)
However, the lens component is a lens in which the object side surface and the image side surface are in contact with air and there is no space between those surfaces, that is, a single lens or a cemented lens,
r ₂₁ is the paraxial radius of curvature of the object side surface of the positive lens component,
r ₂₂ is the paraxial radius of curvature of the image side surface of the positive lens component,
It is. The zoom lens according to claim 16, wherein the following conditional expression (6 ') is satisfied instead of conditional expression (6).
−2 <(r ₂₁ + r ₂₂ ) / (r ₂₁ −r ₂₂ ) <− 0.5 (6 ′) 18. The zoom lens according to claim 1, wherein a lens surface closest to the object side of the second lens group is an aspherical surface. The zoom lens according to any one of claims 15 to 18, wherein the second lens group includes, in order from the object side, a single lens having a positive refractive power, a cemented lens of a positive lens and a negative lens, and a positive refractive power. A zoom lens comprising a single lens. 20. An electronic image pickup apparatus comprising a zoom lens and an electronic image pickup device that is disposed on an image side of the zoom lens and converts an optical image into an electric signal, wherein the zoom lens is according to claim 1. An electronic imaging apparatus, characterized by being a zoom lens.
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