JP2010164606A - Zoom lens and imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which is advantageous in terms of miniaturization, achieving a wide viewing angle and securing a zooming ratio, and which can easily maintain good image quality of a photographed image. <P>SOLUTION: The zoom lens includes in order from an object side: a first lens group G1 having positive, negative, positive and positive refractive power; a second lens group G2; a third lens group G3; and a fourth lens group G4; wherein on zooming from a wide-angle end to a telephoto end, a distance between the first lens group G1 and the second lens group G2 is increased, a distance between the second lens group G2 and the third lens group G3 is decreased, and a distance between the third lens group G3 and the fourth lens group G4 is varied. The first lens group G1 includes two negative and positive lenses. The second lens group G2 has a negative meniscus lens component with a convex surface directed to the object side, located closest to the object side. The third lens group G3 includes, in order from the object side, two positive and negative lenses. The fourth lens group G4 includes one positive lens component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a zoom lens and an image pickup apparatus using the same.

  In recent years, digital cameras that shoot a subject using a solid-state imaging device such as a CCD or CMOS instead of a silver salt film camera have become mainstream. Furthermore, it has come to have a number of categories in a wide range from high-functional types for business use to compact popular types. In the present invention, attention is focused on a category of a compact popular type.

  Users of such popular digital cameras have a desire to enjoy shooting in a wide range of scenes anytime and anywhere. For this reason, digital cameras with a small size in the thickness direction are favored because they are easy to carry in small products, especially clothes and bag pockets. Therefore, further downsizing is demanded. There is also a need for a zoom lens that ensures a high zoom ratio and a wide angle of view so that it can be used in a variety of shooting scenes.

  As a zoom lens that can maintain a relatively high zoom ratio, from the object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power. A zoom lens that includes a lens group and performs zooming by changing the length of each interval between the lens groups is known from the following patent documents.

JP 2008-102165 A JP 2008-102165 A

  However, although the inventions described in Documents 1 and 2 are suitable for reducing the thickness when the zoom lens is housed in the camera body, the angle of view in the diagonal direction at the wide-angle end is only about 65 °. Is.

  The present invention has been made in view of the above problems, and is intended to provide a zoom lens that is advantageous for downsizing, widening the angle of view, ensuring a zoom ratio, and easily maintaining the image quality of a captured image. It is what. It is another object of the present invention to provide a zoom lens that can easily reduce the manufacturing cost. Furthermore, it aims at providing the imaging device provided with such a zoom lens.

  In order to solve the above problems, the zoom lens of the present invention has a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power in order from the object side to the image side. A third lens group and a fourth lens group having positive refracting power, and disposed closer to the image side than the second lens group and closer to the object side than the lens surface closest to the image side in the third lens group; In the zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is widened and the distance between the second lens group and the third lens group is provided. And the distance between the third lens group and the fourth lens group varies.

  Such a type of zoom lens including a positive / negative / positive / positive lens group arrangement is advantageous in securing a zoom ratio. In addition, it is easy to separate the pupil from the image plane for exit, which is advantageous in securing a good image when an electronic image sensor is used.

  In addition, arranging the aperture stop at the above-described position is advantageous for reducing the diameter of the third lens group. If the height of the light beam incident on the third lens group is small, it is advantageous for aberration correction.

  In the zoom lens according to the present invention, the first lens group further includes a negative lens and a positive lens. This is advantageous in reducing the thickness of the first lens group in the thickness direction and the radial direction, and is advantageous in correcting various aberrations in the first lens group by canceling aberrations between the lenses. It makes it easy to suppress aberration fluctuations when the angle is increased and the zoom ratio is increased.

  The second lens group has a negative meniscus lens component having a convex surface on the object side and a concave surface on the image side on the most object side. In addition, the third lens group includes two lenses of a positive lens and a negative lens in order from the object side. The lens component is defined as a lens body having only two refracting surfaces in contact with air on the optical axis, that is, an object-side refracting surface and an image-side refracting surface.

  Reduction of the number of lenses is effective for the compact size when retracted. In the zoom lens of the present invention, the third lens group having the above-described configuration is advantageous in reducing the size of the third lens group, and the main point of the third lens group is located on the second lens group side so that the third lens group can be changed. It is advantageous for securing the double ratio.

  Then, in order to suppress the occurrence of off-axis aberration accompanying the wide angle of view while ensuring sufficient negative refractive power in the second lens group, the lens component closest to the object among the lens components in the second lens group Is the negative meniscus lens component described above. As a result, when the angle of view is increased, the incident angle of off-axis rays incident on the negative lens component near the wide-angle end can be easily suppressed, which is advantageous in reducing off-axis aberrations.

  Then, the fourth lens group is composed of one positive lens component, which is more advantageous for downsizing at the time of retracting.

  In the above-described invention, it is more preferable that any one or more of the following configurations and conditional expressions are simultaneously satisfied.

  The first lens group is preferably positioned closer to the object side at the telephoto end than at the wide angle end.

  Thereby, it becomes easy to ensure the zooming function by the second lens group.

  The negative lens in the first lens group is located closer to the object side than the positive lens in the first lens group, and the negative lens in the first lens group is a paraxial smaller than the absolute value of the paraxial radius of curvature of the object side surface. The positive lens in the first lens group has an image side surface having an absolute value of the paraxial radius of curvature greater than the absolute value of the paraxial radius of curvature of the object side surface. preferable.

  It is advantageous to reduce aberrations while suppressing the thickness of the first lens group on the optical axis. Furthermore, it is more preferable that both the negative lens and the positive lens in the first lens group are meniscus lenses having a convex surface on the object side.

  The incident angle of off-axis rays on each lens surface in the first lens group in the vicinity of the wide-angle end can be reduced, which is advantageous in reducing aberrations when widening the angle of view.

  In order to reduce the relative decentration between the positive lens and the negative lens, it is more preferable to join the positive lens and the negative lens.

  The second lens group preferably includes a positive lens and a negative lens arranged on the image side with respect to the negative meniscus lens component.

  It becomes easy to sufficiently secure the negative refractive power while reducing the aberration of the second lens group, which is advantageous for widening the angle of view. In addition, by securing the refractive power of the second lens group, it becomes easy to suppress the variable magnification burden of the third lens group, which is advantageous in reducing aberration fluctuations during variable magnification.

  In order to reduce the size, it is more preferable that the second lens group includes a negative meniscus lens component and the above-described negative lens and positive lens.

  The second lens group includes a negative meniscus lens component and a rear lens group disposed on the image side of the negative meniscus lens component and having a positive refractive power. The rear lens group includes the positive lens described above. It is more preferable to have a negative lens.

  The principal point of the second lens group can be located on the object side, which is advantageous for reducing the size of the second lens group in the radial direction. That is, it is advantageous for reducing the size when the angle of view is widened.

  In addition, in the vicinity of the wide-angle end, the combined system of the first lens group and the second lens group has a positive refractive power (first lens group), a negative refractive power (negative meniscus lens component), and a positive refractive power (rear lens). Group). Near one telephoto end, the combined system of the second lens group and the third lens group has a negative refractive power (negative meniscus lens component), a positive refractive power (rear lens group), and a positive refractive power (third lens group). Middle positive lens) and negative refractive power (negative lens in the third lens group).

  In this way, both the vicinity of the wide-angle end and the vicinity of the telephoto end have a symmetrical refractive power arrangement that is convenient for aberration correction.

  In the vicinity of the wide-angle end, Petzval sum, coma aberration, and chromatic aberration of magnification cancel each other out in the synthesizing system of the first lens group and the second lens group, which is advantageous for securing the angle of view and securing the performance. In the vicinity of the telephoto end, the Petzval sum, coma aberration, and chromatic aberration of magnification cancel each other out in the synthesizing system of the second lens group and the third lens group, and it is advantageous for securing optical performance when a high zoom ratio is achieved. It becomes.

  The second lens group preferably includes a negative lens having an aspheric surface disposed on the image side of the negative meniscus lens component.

  By using an aspherical surface for the negative lens, it is easy to control the thickness of the second lens group while balancing on-axis aberrations and off-axis aberrations, ensuring a wide angle of view and a zoom ratio. It will be advantageous.

  The negative lens in the second lens group is preferably an aspheric plastic lens.

  Arranging the second negative lens in the second lens group is advantageous in securing the negative refractive power of the second lens group while balancing the on-axis aberration and off-axis aberration together with the negative meniscus lens component. .

  Furthermore, since the negative lens in the rear group has an aspherical surface, it is more advantageous for correcting off-axis aberrations near the wide-angle end while suppressing the thickness of the second lens group. By making the material of the aspherical lens plastic, the aspherical lens can be easily manufactured.

  The third lens group is preferably positioned closer to the object side at the telephoto end than at the wide angle end.

  Thereby, it becomes easy to ensure the zooming function by the third lens group.

  At this time, it is preferable that the aperture stop moves integrally with the third lens group.

  Since the aperture stop moves to the object side at the telephoto end rather than the wide-angle end, it becomes easy to ensure the movement range of the third lens group. In addition, since the aperture stop is close to the third lens group at both the wide-angle end and the telephoto end, it is advantageous for reducing the diameter and thickness of the third lens group.

  The positive lens in the third lens group is preferably a biconvex shape, and the negative lens is preferably a meniscus shape having a convex object side surface and a concave image side surface.

  It is easy to position the principal point of the third lens group on the object side, and it is easy to bring the principal point of the third lens group closer to the second lens group having negative refractive power at the telephoto end, which is advantageous in securing a zoom ratio. It becomes. In addition, the convex surfaces on both sides of the positive lens and the convex surface on the object side surface of the negative component lens are continuously located along the optical axis, thereby converging the axial luminous flux diverging from the second lens group and converging the third lens group. This is even more advantageous for radial downsizing. Then, with the concave surface of the negative lens, the aberration generated on each convex surface of the third lens group is canceled, or the off-axis light beam is refracted in the direction away from the optical axis to secure the height of light incident on the fourth lens group. Thus, it becomes easy to provide a function of improving the telecentricity to the image side of the zoom lens.

  It is preferable that both the object side surface and the image side surface of the positive lens in the third lens group are aspherical surfaces.

  It is advantageous for correcting spherical aberration and coma, and even if the number of lenses in the third lens group is two, it is advantageous for securing optical performance.

  The image side surface of the negative lens in the third lens group is preferably an aspherical surface.

  By making the most image side surface in the third lens group an aspherical surface, the off-axis aberration can be improved.

  It is preferable that the fourth lens group moves toward the object side to perform focusing from a long distance object to a short distance object.

  Since the fourth lens group is easy to reduce in weight and easily reduce the focus sensitivity, it is preferable that the focusing accuracy can be ensured by moving the lens group during focusing.

  Further, since the fourth lens group only needs to have a function of mainly adjusting the exit pupil, the positive refractive power can be reduced. For this reason, the fourth lens group having a single positive lens is advantageous in reducing the size and cost.

  At this time, this positive lens is a meniscus lens having an aspherical surface, which is advantageous for correcting off-axis aberrations. This is particularly effective when the fourth lens group is the most image side lens group.

  In addition, since there are only four lens groups, the first lens group, the second lens group, the third lens group, and the fourth lens group, included in the zoom lens, it is advantageous for downsizing.

  Alternatively, a fifth lens group that is disposed on the image side of the fourth lens group and has a curved refracting surface may be provided. This is advantageous for correcting curvature of field or ensuring telecentricity.

  Furthermore, if the fifth lens group is fixed at the time of zooming from the wide-angle end to the telephoto end, the mechanical configuration can be easily simplified.

  Further, if there are only five lens groups included in the zoom lens, the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group, it is advantageous for miniaturization.

In the zoom lens of each invention described above, more preferable numerical conditions are shown below.

It is preferable that the first lens group satisfies the following conditional expression (1).
−3 <(R _1f + R _1r ) / (R _1f −R _1r ) <− 1 (1)
However,
R _1f is the paraxial radius of curvature of the lens surface closest to the object side of the first lens group,
R _1r is the paraxial radius of curvature of the lens surface closest to the image side of the first lens group,
It is.

  Conditional expression (1) specifies a preferable shape of the first lens group. By making sure that the lower limit of conditional expression (1) is not exceeded and the upper limit is not exceeded, it becomes easy to suppress over or under curvature of field due to widening of the angle of view. In addition, it is advantageous for correcting chromatic aberration of magnification at the telephoto end.

The negative meniscus lens component in the second lens group preferably satisfies the following conditional expression (2).
1 <(R _2nf + R _2nr ) / (R _2nf −R _2nr ) <1.4 (2)
However,
R _2nf is the paraxial radius of curvature of the object side surface of the negative meniscus lens component in the second lens group,
R _2nr is the paraxial radius of curvature of the image side surface of the negative meniscus lens component in the second lens group,
It is.

  Conditional expression (2) specifies a preferable shape of the negative meniscus lens component closest to the object side in the second lens group. By making the object side surface convex so as not to exceed the upper limit of conditional expression (2), it becomes easier to suppress the incident angle of the off-axis light beam incident on the negative meniscus lens component near the wide-angle end. This is advantageous for correcting aberrations. By suppressing the curvature of the image side surface of the negative meniscus lens component so as not to fall below the lower limit of conditional expression (2), it is advantageous for correcting spherical aberration in the vicinity of the telephoto end.

The first lens group and the negative meniscus lens component in the second lens group preferably satisfy the following conditional expression (3).
−0.3 <f _2n / f ₁ <−0.15 (3)
However,
f _2n is the focal length of the negative meniscus lens in the second lens group,
f ₁ is the focal length of the first lens group,
It is.

  Conditional expression (3) specifies a preferable refractive power ratio between the negative meniscus lens component in the first lens group and the second lens group. By making sure that the lower limit of conditional expression (3) is not exceeded, it is possible to sufficiently secure the negative refracting power of the composite system of the first lens group and the negative meniscus lens, which is advantageous for both miniaturization and ensuring the angle of view. Become. Ensuring the positive refracting power of the first lens group without exceeding the upper limit of conditional expression (3) is advantageous for correcting curvature of field.

It is preferable that the negative lens in the third lens group satisfies the following conditional expression (4).
1 <(R _3nf + R _3nr ) / (R _3nf −R _3nr ) <6 (4)
However,
R _3nf is the paraxial radius of curvature of the object side surface of the negative lens in the third lens group,
R _3nr is the paraxial radius of curvature of the image side surface of the negative lens in the third lens group.

  Conditional expression (4) specifies a preferable shape of the negative lens in the third lens group. By making the object side surface of the negative lens group positive refracting power so as not to fall below the lower limit of conditional expression (4), the effect of making the principal point of the third lens group closer to the object, the positive of the third lens group The effect of sharing refractive power can be secured, which is advantageous for downsizing and high zoom ratio. In addition, it is easy to cancel the aberration in the third lens group by securing the negative refractive power of the image side surface. In addition, coma and astigmatism can be easily suppressed by avoiding exceeding the upper limit of conditional expression (4) and avoiding the negative refracting power on the image side surface of the negative lens from becoming too strong.

It is preferable that the negative lens in the third lens group satisfies the following conditional expression (5).
15 <ν _3n <35 (5)
Where ν _3n is the Abbe number of the negative lens in the third lens group.

  Conditional expression (5) specifies a preferred Abbe number of the material of the negative lens in the third lens group. By making sure that the lower limit of conditional expression (5) is not exceeded, an increase in anomalous dispersion of the negative lens material can be suppressed, and an excessive correction function of chromatic aberration can be easily suppressed. Further, securing the dispersion of the negative lens so as not to exceed the upper limit of the conditional expression (5) is advantageous for correcting chromatic aberration in the third lens group.

The positive lens and the negative lens in the third lens group preferably satisfy the following conditional expression (6).
5 <ν _3p −ν _3n <70 (6)
However,
ν _3p is the Abbe number of the positive lens in the third lens group,
ν _3n is the Abbe number of the negative lens in the third lens group,
It is.

  Conditional expression (6) specifies a preferred Abbe number difference between the positive lens and the negative lens in the third lens group. By ensuring that the Abbe number difference between the two lenses does not fall below the lower limit of conditional expression (6), it becomes easier to suppress the occurrence of chromatic aberration in the third lens group, and the occurrence of chromatic aberration in the entire zoom range. It becomes easy to suppress. Further, by making sure that the upper limit of conditional expression (6) is not exceeded, it becomes easy to ensure the cost reduction of lens materials used and the ease of lens processing.

It is preferable that the zoom lens satisfies the following conditional expression (7).
4 <ft / fw (7)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
ft is the focal length of the entire zoom lens system at the telephoto end.

  Conditional expression (7) specifies a preferable zoom ratio of the entire zoom lens system. It is preferable that the zoom ratio is ensured so as not to fall below the lower limit of the conditional expression (7), so that various shooting scenes can be handled.

  In addition, an imaging apparatus according to the present invention includes a zoom lens, and an imaging element that has an imaging surface disposed on the image side and converts an optical image on the imaging surface formed by the zoom lens into an electrical signal. In the imaging apparatus, the zoom lens is any one of the zoom lenses described above.

  Thereby, it is possible to provide an imaging apparatus including a zoom lens that is compact but advantageous in securing a zoom ratio, a field angle, and securing optical performance.

It also has a signal processing circuit that processes the image data obtained by imaging with the imaging device and outputs it as image data whose shape has been changed, and the zoom lens is in the wide-angle end and in the most distant state Therefore, it is preferable that the following conditional expression (8) is satisfied.
_{0.7 <y 07 / (f w} · tanω 07w) <0.99 ··· (8)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
When the distance to the farthest point from the center in the effective image pickup plane of the image pickup device and a y _10,
y ₀₇ = 0.7 × y ₁₀
If effective image pickup area changes at the telephoto end from the wide-angle end, y ₁₀ is the maximum value of the possible values,
ω _07w is an angle formed between the incident light beam and the optical axis in the object space of the principal ray incident on the image position where the image height is y ₀₇ from the center on the imaging surface at the wide angle end.

  In the case of a zoom lens like the present invention, paying attention to the point that astigmatism correction and barrel distortion correction tend to have a trade-off relationship, the distortion aberration is allowed to some extent, and the zoom lens of the present invention is Image shape distortion can be corrected by an image processing function included in the imaging apparatus to be used. This will be described in detail below.

Here, it is assumed that an infinite object is imaged by an optical system having no distortion. In this case, since the image formed has no distortion,
f = y / tan ω (A)
Is established.
Where y is the height of the image point from the optical axis, f is the focal length of the imaging system, and ω is the angle with respect to the optical axis in the object direction corresponding to the image point connected from the center on the imaging surface to the y position. is there.

On the other hand, if the barrel distortion is allowed only when the optical system is near the wide-angle end,
f> y / tan ω (B)
It becomes. In other words, if ω and y are constant values, the focal length f at the wide-angle end may be long, and accordingly, it becomes easier to design with reduced aberrations (particularly astigmatism).

  Therefore, in the imaging apparatus of the present invention, image data obtained by the imaging element is processed by image processing. In this processing, the image data (image shape) is changed so as to correct the barrel distortion. In this way, the finally obtained image data is image data having a shape substantially similar to the object. Therefore, an object image may be output to a CRT or printer based on the image data.

  When such image data correction is performed, the effective imaging area at the wide-angle end has a barrel shape. Then, the image data of the barrel-shaped effective imaging area is changed to substantially rectangular image data.

  Conditional expression (8) defines the degree of barrel distortion at the wide-angle end. By satisfying conditional expression (8), astigmatism can be corrected without difficulty. Note that an image distorted in a barrel shape is photoelectrically converted by an image sensor to become image data distorted in a barrel shape. However, the image data distorted into a barrel shape is electrically processed by an image processing means which is a signal processing system of the electronic imaging apparatus, corresponding to a change in the shape of the image. In this way, even if the image data finally output from the image processing means is reproduced on the display device, the distortion is corrected and an image substantially similar to the subject shape is obtained.

  Here, by suppressing the occurrence of distortion by the zoom lens so as not to fall below the lower limit of the conditional expression (8), when the image distortion due to the distortion of the zoom lens is corrected by the signal processing circuit, the periphery of the corrected image Therefore, it is easy to suppress the deterioration of the sharpness of the peripheral portion of the image.

  Also, by allowing distortion of the zoom lens so as not to exceed the upper limit of the conditional expression (8), it is advantageous for correcting astigmatism of the zoom lens, which is advantageous for making the zoom lens thinner.

  Note that the effective imaging area at the wide-angle end may be determined so as to completely correct the distortion, but considering the influence of the perspective and the peripheral image deterioration, it is appropriate to be around -3% or around -5%. Alternatively, the image data may be changed while leaving barrel distortion.

  Further, if the correction amount of distortion aberration is adjusted for each color signal (for example, R (red), G (green), B (blue)), the chromatic aberration of magnification can be corrected.

  When the above-described zoom lens has a focusing function, each of the above-described configurations is a value in a state where the object at the farthest distance is in focus.

  Moreover, it is preferable that a plurality of the above-described inventions are simultaneously satisfied arbitrarily.

  Moreover, it is preferable to change each of the above-described conditions as follows, since the effect can be more reliably ensured.

  It is more preferable to set the lower limit of conditional expression (1) to −2, more preferably −1.7. Moreover, it is more preferable that the upper limit value of the conditional expression (1) is −1.1, −1.2, and further −1.3.

  More preferably, the lower limit value of conditional expression (2) should be 1.05, more preferably 1.1. Moreover, it is more preferable to set the upper limit of conditional expression (2) to 1.3, more preferably 1.2.

  More preferably, the lower limit value of conditional expression (3) is −0.25, more preferably −0.22. Moreover, it is more preferable that the upper limit value of conditional expression (3) is −0.15, more preferably −0.17.

  More preferably, the lower limit value of conditional expression (4) is 1.5, more preferably 2. Moreover, it is more preferable to set the upper limit of conditional expression (4) to 5.5, and more preferably 5.

  It is more preferable to set the lower limit of conditional expression (5) to 15.5, more preferably 16. Moreover, it is more preferable to set the upper limit of conditional expression (5) to 30 and further to 25.

  More preferably, the lower limit value of conditional expression (6) is set to 15, 40, and 55. In addition, it is more preferable that the upper limit value of conditional expression (6) is 68, more preferably 66.

  It is more preferable that the lower limit value of conditional expression (7) is set to 5 and further 6. In addition, it is preferable to set an upper limit value of conditional expression (7) so that it does not exceed 10 because the overall length can be reduced and fluctuations in aberration can be suppressed.

  It is more preferable to set the lower limit of conditional expression (8) to 0.7, more preferably 0.75. More preferably, the upper limit value of conditional expression (8) is 0.98, 0.95, or 0.92.

  According to the present invention, it is possible to provide a zoom lens that is advantageous in reducing the size, widening the angle of view, and securing a zoom ratio, and that can easily maintain the image quality of a captured image. In addition, it is possible to provide a zoom lens that can easily reduce the manufacturing cost. Furthermore, an imaging apparatus provided with such a zoom lens can be provided.

FIG. 2 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the zoom lens of the present invention. It is the same figure as FIG. 1 of Example 2 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 3 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom lens of this invention. 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. It is a figure which shows correction | amendment of a distortion aberration. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 13 is a rear perspective view of the digital camera of FIG. 12. It is sectional drawing of the digital camera of FIG. FIG. 13 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 12.

  In any of the embodiments based on the present invention described below, the above-described constituent elements are related to each other, so that a zoom ratio of about 7 times is ensured and the number of constituent lenses is small while being wide angle of view. This zoom lens is advantageous in reducing the size of the zoom lens and is easy to ensure optical performance.

  Examples 1 to 5 of the zoom lens according to the present invention will be described below. FIGS. 1 to 5 show lens cross-sectional views of Example 1 to Example 5 at (a) a wide angle end when focusing on an object point at infinity, (b) an intermediate state, and (c) a telephoto end, respectively.

  In each figure, the first lens group is G1, the second lens group is G2, the brightness stop is S, the third lens group is G3, the fourth lens group is G4, the optical low-pass filter with IR cut coat is F, and the electron The cover glass of the CCD that is the image sensor is indicated by C, and the image surface of the CCD is indicated by I. As for the IR cut coat, for example, the optical low pass filter F may be coated directly, or an infrared cut absorption filter may be arranged separately.

  In each embodiment, the fourth lens group G4 is extended to perform focusing from a long distance object to a short distance object.

  The aperture stop S has a fixed aperture size, and a convex surface that is the object side surface of the third lens group G3 is inserted into the aperture of the aperture stop S.

  Further, the exposure amount adjustment at the time of photographing is performed by inserting or removing the light amount adjustment filter (not shown) that moves together with the third lens group G3 immediately after the image side of the third lens group G3 into the optical path, and mechanical shutter (not used). (Shown).

  The plastic lens is used for the fourth lens group G4 in the first and second embodiments, and is used for the biconcave lens and the fourth lens group G4 in the second lens group G2 in the third and fourth embodiments. Used for the fourth lens group G4 and the fifth lens group G5.

  As shown in FIG. 1, the zoom lens of Example 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens unit having a positive refractive power. 3 lens group G3 and 4th lens group G4 of positive refractive power are comprised.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the object side from the wide-angle end to the telephoto end.

  The second lens group G2 moves from the wide-angle end to the intermediate state and moves toward the image side while increasing the distance from the first lens group G1 and narrowing the distance from the third lens group G3, and from the intermediate state to the telephoto end. The distance from the first lens group G1 is increased, and the distance from the third lens group G3 is decreased, and the object is moved to the object side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 and the aperture stop S move toward the object side from the wide-angle end to the telephoto end while narrowing the distance from the second lens group G2 and increasing the distance from the fourth lens group G4.

  The fourth lens group G4 moves from the wide-angle end to the intermediate state, moves toward the object side while widening the distance from the third lens group G3 and widening the distance from the image plane I, and moves from the intermediate state to the telephoto end. The distance to the lens group G3 is increased, and the distance to the image plane I is reduced, and the image side is moved to the image side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of 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, and the second lens group G2 has a convex surface facing the object side. , A negative meniscus lens having a convex surface, a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side. The third lens group G3 includes an aperture stop S, a biconvex positive lens, and an object side. The fourth lens group G4 includes one positive meniscus lens having a convex surface directed toward the object side.

  The aspherical surfaces are both surfaces of the biconcave negative lens of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, the image side surface of the negative meniscus lens, and the object of the positive meniscus lens of the fourth lens group G4. It is used for 6 sides.

  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 positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens unit having a positive refractive power. 3 lens group G3 and 4th lens group G4 of positive refractive power are comprised.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the object side from the wide-angle end to the telephoto end.

  The second lens group G2 moves from the wide-angle end to the intermediate state and moves toward the image side while increasing the distance from the first lens group G1 and narrowing the distance from the third lens group G3, and from the intermediate state to the telephoto end. The distance from the first lens group G1 is increased, and the distance from the third lens group G3 is decreased, and the object is moved to the object side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 and the aperture stop S move toward the object side from the wide-angle end to the telephoto end while narrowing the distance from the second lens group G2 and increasing the distance from the fourth lens group G4.

  The fourth lens group G4 moves from the wide-angle end to the intermediate state, moves toward the object side while widening the distance from the third lens group G3 and widening the distance from the image plane I, and moves from the intermediate state to the telephoto end. The distance to the lens group G3 is increased, and the distance to the image plane I is reduced, and the image side is moved to the image side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of 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, and the second lens group G2 has a convex surface facing the object side. A negative meniscus lens having a convex surface facing the image side, a negative meniscus lens having a convex surface facing the image side, and a negative meniscus lens having a convex surface facing the image side. The third lens group G3 includes an aperture stop S and a biconvex positive lens. The fourth lens group G4 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.

  The aspherical surfaces are the image side surface of the negative meniscus lens on the image side of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, the image side surface of the negative meniscus lens, and the surface of the fourth lens group G4. It is used for five surfaces on the image side of the positive meniscus lens.

  As shown in FIG. 3, the zoom lens of Example 3 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens unit having a positive refractive power. 3 lens group G3 and 4th lens group G4 of positive refractive power are comprised.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the object side from the wide-angle end to the telephoto end.

  The second lens group G2 moves from the wide-angle end to the intermediate state and moves toward the image side while increasing the distance from the first lens group G1 and narrowing the distance from the third lens group G3, and from the intermediate state to the telephoto end. The distance from the first lens group G1 is increased, and the distance from the third lens group G3 is decreased, and the object is moved to the object side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 and the aperture stop S move toward the object side from the wide-angle end to the telephoto end while narrowing the distance from the second lens group G2 and widening the distance from the fourth lens group G4.

  The fourth lens group G4 moves from the wide-angle end to the intermediate state, moves toward the object side while widening the distance from the third lens group G3 and widening the distance from the image plane I, and moves from the intermediate state to the telephoto end. The distance to the lens group G3 is increased, and the distance to the image plane I is reduced, and the image side is moved to the image side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of 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, and the second lens group G2 has a convex surface facing the object side. , A negative meniscus lens having a convex surface, a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side. The third lens group G3 includes an aperture stop S, a biconvex positive lens, and an object side. The fourth lens group G4 includes one positive meniscus lens having a convex surface directed toward the object side.

  The aspheric surfaces are the image side surface of the biconcave negative lens of the second lens group G2, the double side of the biconvex positive lens of the third lens group G3, the image side surface of the negative meniscus lens, and the positive meniscus of the fourth lens group G4. It is used for five surfaces on the image side of the lens.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens unit having a positive refractive power. 3 lens group G3 and 4th lens group G4 of positive refractive power are comprised.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the object side from the wide-angle end to the telephoto end.

  The second lens group G2 moves from the wide-angle end to the intermediate state and moves toward the image side while increasing the distance from the first lens group G1 and narrowing the distance from the third lens group G3, and from the intermediate state to the telephoto end. The distance from the first lens group G1 is increased, and the distance from the third lens group G3 is decreased, and the object is moved to the object side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 and the aperture stop S move toward the object side from the wide-angle end to the telephoto end while narrowing the distance from the second lens group G2 and increasing the distance from the fourth lens group G4.

  The fourth lens group G4 moves from the wide-angle end to the intermediate state, moves toward the object side while widening the distance from the third lens group G3 and widening the distance from the image plane I, and moves from the intermediate state to the telephoto end. The distance to the lens group G3 is increased, and the distance to the image plane I is reduced, and the image side is moved to the image side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  In order from the object side, the first lens group G1 includes a cemented lens of 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, and the second lens group G2 has a convex surface facing the object side. , A negative meniscus lens having a convex surface, a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side. The third lens group G3 includes an aperture stop S, a biconvex positive lens, and an object side. The fourth lens group G4 includes one positive meniscus lens having a convex surface directed toward the object side.

The aspheric surfaces are the image side surface of the biconcave negative lens of the second lens group G2, the double side of the biconvex positive lens of the third lens group G3, the image side surface of the negative meniscus lens, and the positive meniscus of the fourth lens group G4. It is used for five surfaces on the image side of the lens.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a first lens unit having a positive refractive power. The lens unit includes a three-lens group G3, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power.

  The movement state when zooming from the wide-angle end to the telephoto end is shown below.

  The first lens group G1 moves toward the object side from the wide-angle end to the telephoto end.

  The second lens group G2 moves from the wide-angle end to the intermediate state and moves toward the image side while increasing the distance from the first lens group G1 and narrowing the distance from the third lens group G3, and from the intermediate state to the telephoto end. The distance from the first lens group G1 is increased, and the distance from the third lens group G3 is decreased, and the object is moved to the object side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The third lens group G3 and the aperture stop S move toward the object side from the wide-angle end to the telephoto end while narrowing the distance from the second lens group G2 and increasing the distance from the fourth lens group G4.

  The fourth lens group G4 moves from the wide-angle end to the intermediate state, moves toward the object side while widening the distance from the third lens group G3 and widening the distance from the image plane I, and moves from the intermediate state to the telephoto end. The distance to the lens group G3 is increased, and the distance to the image plane I is reduced, and the image side is moved to the image side. At the telephoto end, it is positioned closer to the object side than the wide-angle end.

  The fourth lens group G4 is fixed.

  In order from the object side, the first lens group G1 includes a cemented lens of 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, and the second lens group G2 has a convex surface facing the object side. , A negative meniscus lens having a convex surface, a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side. The third lens group G3 includes an aperture stop S, a biconvex positive lens, and an object side. The fourth lens group G4 is composed of one biconvex positive lens, and the fifth lens group G5 is composed of one positive meniscus lens having a convex surface facing the image side.

  The aspheric surfaces are the double-sided negative lens of the second lens group G2, the double-sided positive lens of the third lens group G3, the image side surface of the negative meniscus lens, and the double-convex positive lens of the fourth lens group G4. It is used for seven surfaces on the object side, the object side surface of the positive meniscus lens in the fourth lens group G4.

  The numerical data of the lens in each example is shown below.

In the numerical data of the lens in each embodiment, r is the radius of curvature of each lens surface, d is the thickness or spacing of each lens, nd is the refractive index at the d-line of each lens, and νd is the Abbe at the d-line of each lens. Number, K is a conical coefficient, A4, A6, A8, and A10 are aspheric coefficients, and E ± N is × 10 ± ^N. The total length is obtained by adding the back focus BF to the distance on the optical axis from the entrance surface to the exit surface of the lens. The full length and the back focus BF are shown as air equivalent lengths. The value corresponding to the conditional expression in each embodiment is a value in a state where an object point at infinity is in focus.

  In each embodiment, regardless of the focal length of the entire zoom lens system, the angle of view change when the image height is fixed, the angle of view change when the distortion aberration is electrically corrected, and the value of the image height change. Is also described. In order to electrically correct barrel distortion (distortion) that occurs near the wide-angle end, the effective imaging area at the wide-angle end is barrel-shaped, so the image height is intermediate and the image at the telephoto end. The value is smaller than high.

  Each aspheric shape is expressed by the following expression using each aspheric coefficient in each embodiment.

Z = (Y ² / r) / [1+ {1− (1 + K) · (Y / r) ² } ^1/2 ]
+ A4 × Y ⁴ + A6 × Y ⁶ + A8 × Y ⁸ + A10 × Y ¹⁰
However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.

Numerical example 1
Unit mm

Surface data surface number r d nd νd
1 17.791 0.81 1.84666 23.78
2 12.005 3.08 1.77250 49.60
3 86.709 Variable
4 66.506 0.75 1.88300 40.76
5 4.480 2.46
6 (Aspherical surface) -31.306 0.65 1.58313 59.38
7 (Aspherical) 13.781 0.10
8 12.506 1.29 1.92286 18.90
9 315.181 Variable
10 (Aperture) ∞ -0.40
11 (Aspherical surface) 4.358 2.44 1.49700 81.61
12 (Aspherical surface) -12.005 0.10
13 7.191 1.31 2.10225 16.80
14 (Aspherical) 4.388 Variable
15 (Aspherical surface) 9.676 1.58 1.52542 55.78
16 45.813 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane ∞

Aspheric data 6th surface
K = 0.000, A4 = -8.08347E-04, A6 = 3.75656E-05, A8 = -8.70154E-07, A10 = -2.10000E-08
7th page
K = 0.000, A4 = -1.28371E-03, A6 = 4.25827E-05, A8 = -2.31366E-06
11th page
K = -0.740, A4 = 3.67824E-04, A6 = -2.24188E-05, A8 = 1.19854E-06
12th page
K = -5.083, A4 = 1.16962E-03, A6 = -2.27613E-04, A8 = 1.88604E-05
14th page
K = -3.443, A4 = 5.43899E-03, A6 = 1.19187E-04
15th page
K = 0.361, A4 = -1.48739E-04, A6 = 3.33684E-06, A8 = -1.10231E-07, A10 = -3.35750E-10

Zoom data (when the image height is constant at 3.83)
Wide angle Medium Telephoto focal length 5.07 12.87 34.28
F number 3.11 4.03 6.05
Angle of view 81.57 33.35 12.50

d3 0.30 6.25 11.70
d9 11.13 3.86 0.70
d14 5.45 6.59 18.30
d16 2.65 5.99 3.78

BF 4.19 7.54 5.35
Total lens length 35.24 38.40 50.21

Zoom lens group data Group Start surface Focal length
1 1 29.89
2 4 -6.08
3 11 8.95
4 15 23.00

Zoom data (when distortion is corrected electrically)
Wide angle Medium Telephoto focal length 5.07 12.87 34.28
F number 3.11 4.03 6.05
Angle of view 75.77 33.35 12.50
Image height 3.51 3.83 3.83

Numerical example 2
Unit mm

Surface data surface number r d nd νd
1 18.084 0.81 1.84666 23.78
2 11.051 3.10 1.81600 46.62
3 75.670 Variable
4 57.210 0.75 1.81600 46.62
5 4.021 2.19
6 -59.513 1.21 1.93067 19.09
7 -10.809 0.37
8 -7.550 0.70 1.58313 59.38
9 (Aspherical) -84.807 Variable
10 (Aperture) ∞ -0.30
11 (Aspherical) 4.636 2.56 1.49700 81.61
12 (Aspherical surface) -8.016 0.10
13 6.444 1.18 2.10225 16.80
14 (Aspherical) 4.080 Variable
15 9.893 1.60 1.52542 55.78
16 (Aspherical) 52.976 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane ∞

Aspheric data 9th surface
K = 516.240, A4 = -9.02519E-04, A6 = -2.11145E-05
11th page
K = -3.042, A4 = 2.08503E-03, A6 = -1.44832E-04
12th page
K = 1.146, A4 = 9.60208E-04, A6 = -9.14080E-05
14th page
K = -0.544, A4 = 1.26081E-03, A6 = 1.76501E-04, A8 = 5.49600E-07
16th page
K = 0.000, A4 = 6.63364E-05, A6 = -1.83062E-06

Zoom data (when the image height is constant at 3.83)
Wide angle Medium Telephoto focal length 5.06 12.84 34.18
F number 3.08 4.02 6.04
Angle of view 81.97 33.35 12.57

d3 0.30 6.18 11.70
d9 8.93 2.97 0.60
d14 5.30 5.92 18.08
d16 2.60 6.44 3.80

BF 4.11 7.97 5.33
Total lens length 32.90 37.31 49.98

Zoom lens group data Group Start surface Focal length
1 1 29.12
2 4 -5.36
3 11 8.11
4 15 22.86

Zoom data (when distortion is corrected electrically)
Wide angle Medium Telephoto focal length 5.06 12.84 34.18
F number 3.08 4.02 6.04
Angle of view 75.98 33.35 12.57
Image height 3.50 3.83 3.83

Numerical Example 3
Unit mm

Surface data surface number r d nd νd
1 20.001 0.81 1.84666 23.78
2 12.364 3.07 1.81600 46.62
3 124.634 Variable
4 94.246 0.75 1.88300 40.76
5 4.500 2.36
6 -34.701 0.70 1.52542 55.78
7 (Aspherical) 12.915 0.10
8 9.855 1.24 1.94595 17.98
9 31.445 Variable
10 (Aperture) ∞ -0.30
11 (Aspherical) 4.101 2.21 1.49700 81.61
12 (Aspherical surface) -10.543 0.30
13 9.216 1.34 2.00170 19.30
14 (Aspherical) 4.773 Variable
15 9.600 1.59 1.52542 55.78
16 (Aspherical) 44.033 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane ∞

Aspheric data 7th surface
K = 0.095, A4 = -4.32632E-04, A6 = -2.55053E-06, A8 = -1.11152E-06
11th page
K = -1.078, A4 = 1.00474E-03, A6 = -5.56504E-05
12th page
K = 0.000, A4 = 1.45394E-03, A6 = -2.47470E-04, A8 = 1.52715E-05
14th page
K = -1.142, A4 = 2.30205E-03, A6 = 3.35770E-04
16th page
K = 0.000, A4 = 1.16219E-04, A6 = -5.73103E-06, A8 = 1.27697E-07

Zoom data (when the image height is constant at 3.83)
Wide angle Medium telephoto focal length 5.08 12.86 34.21
F number 3.10 4.05 6.04
Angle of view 81.47 33.09 12.53

d3 0.30 6.22 11.70
d9 10.48 3.72 0.70
d14 5.36 6.57 17.85
d16 2.47 5.82 3.93

BF 4.00 7.35 5.46
Total lens length 34.30 38.02 49.87

Zoom lens group data Group Start surface Focal length
1 1 29.49
2 4 -5.89
3 11 8.62
4 15 23.00

Zoom data (when distortion is corrected electrically)
Wide angle Medium telephoto focal length 5.08 12.86 34.21
F number 3.10 4.05 6.04
Angle of view 75.69 33.09 12.53
Image height 3.51 3.83 3.83

Numerical Example 4
Unit mm

Surface data surface number r d nd νd
1 19.436 0.81 1.84666 23.78
2 12.179 3.01 1.80400 46.57
3 120.343 Variable
4 91.118 0.75 1.88300 40.76
5 4.500 2.36
6 -22.299 0.70 1.52542 55.78
7 (Aspherical) 16.643 0.10
8 11.204 1.24 1.94595 17.98
9 51.000 Variable
10 (Aperture) ∞ -0.30
11 (Aspherical) 4.082 2.12 1.49700 81.61
12 (Aspherical surface) -9.935 0.30
13 11.164 1.43 1.92287 20.80
14 (Aspherical) 4.922 Variable
15 9.605 1.59 1.52542 55.78
16 (Aspherical) 44.252 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane ∞

Aspheric data 7th surface
K = 2.468, A4 = -5.09398E-04, A6 = 1.08408E-07, A8 = -1.20478E-06
11th page
K = -1.082, A4 = 1.03781E-03, A6 = -5.80705E-05
12th page
K = 0.000, A4 = 1.63732E-03, A6 = -2.60167E-04, A8 = 1.54732E-05
14th page
K = -1.174, A4 = 2.25831E-03, A6 = 3.49404E-04
16th page
K = 0.000, A4 = 1.14861E-04, A6 = -5.05049E-06, A8 = 1.15219E-07

Zoom data (when the image height is constant at 3.83)
Wide angle Medium telephoto focal length 5.07 12.85 34.21
F number 3.12 4.06 6.04
Angle of view 81.60 33.14 12.53

d3 0.30 6.21 11.68
d9 10.92 3.86 0.70
d14 5.36 6.60 17.86
d16 2.57 5.90 4.05

BF 4.10 7.43 5.58
Total lens length 34.78 38.20 49.92

Zoom lens group data Group Start surface Focal length
1 1 29.40
2 4 -6.00
3 11 8.83
4 15 22.99

Zoom data (when distortion is corrected electrically)
Wide angle Medium Telephoto focal length 5.07 12.85 34.21
F number 3.12 4.06 6.04
Angle of view 75.87 33.14 12.53
Image height 3.51 3.83 3.83

Numerical Example 5
Unit mm

Surface data surface number r d nd νd
1 17.912 0.80 1.84666 23.78
2 12.037 2.98 1.77250 49.60
3 85.075 Variable
4 52.269 0.75 1.88300 40.76
5 4.500 2.41
6 (Aspherical surface) -30.820 0.60 1.58313 59.38
7 (Aspherical) 14.570 0.10
8 10.821 1.24 1.94595 17.98
9 42.997 Variable
10 (Aperture) ∞ -0.30
11 (Aspherical surface) 4.174 1.89 1.49700 81.61
12 (Aspherical surface) -12.814 0.10
13 6.462 1.35 2.10225 16.80
14 (Aspherical) 3.994 Variable
15 (Aspherical) 15.000 1.48 1.52542 55.78
16 -60.061 Variable
17 (Aspherical) 15.000 0.80 1.52542 55.78
18 -14.474 0.10
19 ∞ 0.30 1.51633 64.14
20 ∞ 0.50
21 ∞ 0.50 1.51633 64.14
22 ∞ 0.50
Image plane ∞

Aspheric data 6th surface
K = 7.548, A4 = -7.20453E-04, A6 = 4.60250E-06
7th page
K = -19.224, A4 = -3.45511E-04, A6 = -1.38155E-05
11th page
K = -0.986, A4 = 7.82686E-04, A6 = -9.16230E-05
12th page
K = -4.094, A4 = 1.33854E-04, A6 = -1.75238E-04, A8 = 1.11412E-05
14th page
K = -0.696, A4 = 2.85239E-03, A6 = 2.68798E-04
15th page
K = 0.000, A4 = 4.22970E-05, A6 = -4.51175E-06
16th page
K = 0.000, A4 = -5.73220E-04, A6 = 2.60520E-05

Zoom data (when the image height is constant at 3.83)
Wide angle Medium telephoto focal length 5.06 12.86 34.09
F number 3.14 4.03 6.04
Angle of View 81.51 32.86 12.55

d3 0.25 6.34 11.70
d9 11.22 3.94 0.70
d14 5.53 6.01 16.90
d16 2.00 5.69 4.59

BF 1.59 1.63 1.63
Total lens length 34.79 37.82 49.73

Zoom lens group data Group Start surface Focal length
1 1 30.33
2 4 -5.99
3 11 8.60
4 15 23.00
5 17 515.19

Zoom data (when distortion is corrected electrically)
Wide angle Medium telephoto focal length 5.08 12.86 34.09
F number 3.14 4.03 6.04
Angle of view 75.88 32.86 12.55
Image height 3.52 3.83 3.83

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 5 are shown in FIGS. In these aberration diagrams, (a) shows the wide-angle end, (b) the intermediate state, and (c) spherical aberration SA, astigmatism AS, distortion DT, and lateral chromatic aberration CC at the telephoto end. FNO represents an F number, and ω represents a half angle of view.

Next, the condition values and the conditional expressions (1) to (7) and the values of y ₀₇ , fw, and ω _{07w in} the above embodiments will be shown.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5
(1) -1.516 -1.628 -1.382 -1.385 -1.533
(2) 1.144 1.151 1.1 1.104 1.188
(3) -0.183 -0.183 -0.182 -0.183 -0.185
(4) 4.131 4.453 3.149 2.577 4.235
(5) 16.8 16.8 19.3 20.8 16.8
(6) 64.81 64.81 62.31 60.81 64.81
(7) 6.757 6.76 6.732 6.753 6.730
(8) 0.983 0.930 0.929 0.927 0.935
y ₀₇ 2.43 2.55 2.55 2.55 2.68
fw 5.07 5.06 5.08 5.07 5.06
ω _07w 28.24 29.67 29.57 29.69 29.5

  In each embodiment, the following configuration may be adopted.

  In the zoom lens of this embodiment, barrel distortion occurs at the wide-angle end on the rectangular photoelectric conversion surface. On the other hand, the occurrence of distortion is suppressed near the intermediate focal length state and at the telephoto end. In order to electrically correct the distortion, the effective imaging area is preferably barrel-shaped at the wide-angle end and rectangular at the intermediate focal length state or the telephoto end. Then, the effective imaging area set in advance is image-converted by image processing and converted into rectangular image information with reduced distortion. The image height IHw at the wide-angle end is made smaller than the image height IHs at the intermediate focal length state and the image height IHt at the telephoto end.

  As shown in FIG. 11, the magnification on the circumference (image height) of the radius R inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface is fixed, and this circumference is corrected. The standard. 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. 11, 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 on the radius r ₂ ′ (ω) circumference to be corrected in a direction away from the center of the circle. To point Q ₂ . Here, r ′ (ω) can be expressed as follows.
r ′ (ω) = αftanω (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 the other points on the circumference of the circle (image height) of radius r (ω) are moved in a substantially radial direction to obtain a radius r ′ ( If correction can be performed by moving the concentric circles so that ω), it is considered advantageous in terms of data amount and calculation amount.

However, the optical image is no longer a continuous amount (due to sampling) when captured by the electronic image sensor. Therefore, strictly speaking, the circle with the radius R drawn on the optical image is not an accurate circle unless the pixels on the electronic image sensor are arranged radially. That is, in the shape correction of the image data represented for each discrete coordinate point, there is no circle that can fix the magnification. Therefore, it is preferable to use a method of determining the coordinates (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 of 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 pixels, 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) = αftanω
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. Then, in the vicinity of the telescope in the divided zone, approximately r ′ (ω) = αftanω
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 / tanω
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 / tanω
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.

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

  In general, in an electronic still camera, an image of a subject is separated into three primary color images of a first primary color, a second primary color, and a third primary color, and a color image is reproduced by superimposing respective output signals by calculation. I have to. When the zoom lens has chromatic aberration of magnification, the image of the first primary color is formed at the position where the image of the second primary color and the third primary light is formed, considering the image of the first primary color as a reference. Will deviate from the position. In order to electronically correct the magnification chromatic aberration of the image, the amount of deviation of the imaging position of the light of the second primary color and the third primary color with respect to the first primary color is determined for each pixel of the image sensor based on the aberration information of the zoom lens. Find in advance. Then, coordinate conversion may be performed for each pixel of the captured image so as to correct only the amount of deviation from the first primary color.

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

  The chromatic aberration of magnification varies depending on the zoom, focus, and aperture value, but for each lens position (zoom, focus, and aperture value), the shift amounts of the second primary color and the third primary color from the first primary color are stored and retained as correction data. It may be stored in the device. By referring to the correction data in accordance with the zoom position, it is possible to output the second and third primary color signals in which the deviation of the second and third primary colors from the first primary color signal is corrected.

  Further, in order to cut unnecessary light such as ghosts and flares, a flare stop other than the brightness stop may be arranged.

  Object side of the first lens group, between the first and second lens groups, between the second and third lens groups, between the third and fourth lens groups, between the fourth and fifth lens groups, and from the most image side group to the image plane You may arrange in any place. The frame member may be configured to cut flare rays, or another member may be configured. Also, it may be printed directly on the optical system, painted, or bonded with a seal. The shape may be any shape such as a circle, an ellipse, a rectangle, a polygon, or a range surrounded by a function curve. Further, not only harmful light beams but also light beams such as coma flare around the screen may be cut.

  Each lens may be provided with an antireflection coating to reduce ghosts and flares. A multi-coat is desirable because it can effectively reduce ghost and flare. Infrared cut coating may be applied to the lens surface, cover glass, or the like.

  Further, the brightness (shading) at the periphery of the image may be reduced by shifting the CCD microlens. For example, the design of the CCD microlens may be changed according to the incident angle of the light beam at each image height. Further, the amount of decrease in the peripheral portion of the image may be corrected by image processing.

  In order to prevent the occurrence of ghost and flare, it is common practice to apply an antireflection coating to the air contact surface of the lens. On the other hand, the refractive index of the adhesive is sufficiently higher than the refractive index of air on the cemented surface of the cemented lens. For this reason, the reflectance is often the same as or lower than that of a single-layer coating, and it is rare to apply a coating. However, if an anti-reflection coating is also applied to the joint surface, ghosts and flares can be further reduced, and still better images can be obtained.

  In particular, recently, high refractive index glass materials have become widespread and have been used extensively in camera optical systems because of their high aberration correction effects. However, when high refractive index glass materials are used as cemented lenses, reflection at the cemented surface is also possible. It can no longer be ignored. In such a case, it is particularly effective to provide an antireflection coating on the joint surface.

  Effective use of the bonding surface coat is disclosed in JP-A-2-27301, JP-A-2001-324676, JP-A-2005-92115, USP7116482, and the like.

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

  As a matter of course, the coating on the bonding surface may be a multi-coat as in the coating on the air contact surface of the lens. By appropriately combining two or more layers of coating materials and film thicknesses, it becomes possible to further reduce the reflectance and control the spectral characteristics and angular characteristics of the reflectance. Needless to say, it is effective to coat the cemented surfaces other than the first lens group based on the same concept.

  12 to 14 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. 12 is a front perspective view showing the appearance of the digital camera 40, FIG. 13 is a rear front view thereof, and FIG. 14 is a schematic cross-sectional view showing the configuration of the digital camera 40. However, FIGS. 12 and 14 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 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. When the cover 60 is opened and the camera 40 is set to the shooting state, the shooting optical system 41 enters the non-collapsed state shown in FIG. Imaging is performed through the optical system 41, for example, the zoom lens of Example 1, and an object image formed by the imaging optical system 41 is captured by the imaging surface of the CCD 49 through the low-pass filter F and the cover glass C on which the wavelength band limiting coating is applied. It is formed on (photoelectric conversion surface).

  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. In addition, a recording means 52 is connected to the processing means 51 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 a floppy disk ( The recording and writing may be performed electronically using a registered trademark, a memory card, an 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. 15 is a block diagram of the internal circuit of the main part of the digital camera 40. In the following description, the processing unit 51 includes, for example, the CDS / ADC unit 24, the primary storage memory 17, the image processing unit 18, and the storage unit 52 includes the storage medium unit 19, for example.

  As shown in FIG. 15, 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 primary 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 primary 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 so that data can be input or output 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 photographing drive circuit 16 and converts the light amount of each pixel of the object image into an electrical signal and outputs it 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 memory 17.

  The primary storage memory 17 is a buffer made of, for example, SDRAM, 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 primary 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 storage 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 primary 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. In addition, fast focusing operation on the wide-angle side and the telephoto side is possible.

  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.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group G5 ... 5th lens group S ... Brightness diaphragm F ... Optical low-pass filter C ... Cover glass I ... Image plane E ... observer eyeball 12 ... operation unit 13 ... control units 14, 15 ... bus 16 ... imaging drive circuit 17 ... primary storage memory 18 ... image processing unit 19 ... storage medium unit 20 ... display unit 21 ... setting information storage memory unit 22 ... Bus 24 ... CDS / ADC section 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 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 ... Focus Distance change button 62 ... Setting change switch

Claims (29)

From the object side to the image side,
A first lens group having positive refractive power;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having positive refractive power;
Have
An aperture stop disposed on the image side of the second lens group and on the object side of the most image side lens surface in the third lens group;
When zooming from the wide-angle end to the telephoto end,
The distance between the first lens group and the second lens group is widened,
The interval between the second lens group and the third lens group is narrowed,
The distance between the third lens group and the fourth lens group varies,
The first lens group includes two lenses, a negative lens and a positive lens,
The second lens group has a negative meniscus lens component with a convex surface facing the object side closest to the object side,
The third lens group is composed of two lenses, a positive lens and a negative lens, in order from the object side.
The zoom lens according to claim 4, wherein the fourth lens group includes one positive lens component. The zoom lens according to claim 1, wherein the first lens group is located closer to the object side at a telephoto end than at a wide angle end. The negative lens in the first lens group is located closer to the object side than the positive lens in the first lens group;
The negative lens in the first lens group has an image side surface having an absolute value of a paraxial curvature radius smaller than an absolute value of a paraxial radius of curvature of an object side surface;
3. The positive lens in the first lens group has an image side surface having an absolute value of a paraxial curvature radius that is larger than an absolute value of a paraxial curvature radius of an object side surface. Zoom lens described in 1. 4. The zoom lens according to claim 1, wherein each of the negative lens and the positive lens in the first lens group is a meniscus lens having a convex surface directed toward the object side. 5. The zoom lens according to any one of claims 1 to 4, wherein the negative lens and the positive lens in the first lens group are cemented. 6. The zoom lens according to claim 1, wherein the second lens group includes a positive lens and a negative lens arranged on the image side of the negative meniscus lens component. The zoom lens according to claim 6, wherein the second lens group includes the negative meniscus lens component, the positive lens, and the negative lens. The second lens group includes the negative meniscus lens component, and a rear lens group disposed on the image side of the negative meniscus lens component and having a positive refractive power.
The zoom lens according to any one of claims 1 to 5, wherein the rear lens group includes a positive lens and a negative lens. 6. The zoom lens according to claim 1, wherein the second lens group includes a negative lens having an aspheric surface arranged on the image side of the negative meniscus lens component. The zoom lens according to claim 6, wherein the negative lens in the second lens group is an aspheric plastic lens. The zoom lens according to claim 1, wherein the third lens group is located closer to the object side at the telephoto end than at the wide-angle end. The zoom lens according to any one of claims 1 to 11, wherein the brightness stop moves integrally with the third lens group. 13. The positive lens in the third lens group has a biconvex shape, and the negative lens has a meniscus shape having a convex surface facing the object side. Zoom lens. The zoom lens according to claim 1, wherein both the object side surface and the image side surface of the positive lens in the third lens group are aspherical surfaces. The zoom lens according to claim 1, wherein an image side surface of the negative lens in the third lens group is an aspherical surface. The zoom lens according to claim 1, wherein the fourth lens group moves toward the object side and performs focusing from a long-distance object to a short-distance object. The zoom lens according to any one of claims 1 to 16, wherein the fourth lens group includes a single positive lens. The zoom lens according to any one of claims 1 to 17, wherein the fourth lens group includes a meniscus lens having an aspherical surface. 2. The lens group included in the zoom lens includes only four of the first lens group, the second lens group, the third lens group, and the fourth lens group. The zoom lens according to claim 18. The zoom lens has a fifth lens group that is disposed on the image side of the fourth lens group and has a curved refractive surface,
The fifth lens group is fixed at the time of zooming from the wide-angle end to the telephoto end,
The zoom lens includes only five lens groups: the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group. The zoom lens according to any one of claims 1 to 18. The zoom lens according to any one of claims 1 to 20, wherein the first lens group satisfies the following conditional expression (1).
−3 <(R _1f + R _1r ) / (R _1f −R _1r ) <− 1 (1)
However,
R _1f is the paraxial radius of curvature of the lens surface closest to the object side of the first lens group,
R _1r is the paraxial radius of curvature of the lens surface closest to the image side of the first lens group,
It is. The zoom lens according to any one of claims 1 to 21, wherein the negative meniscus lens component in the second lens group satisfies the following conditional expression (2).
1 <(R _2nf + R _2nr ) / (R _2nf −R _2nr ) <1.4 (2)
However,
R _2nf is the paraxial radius of curvature of the object side surface of the negative meniscus lens component in the second lens group,
R _2nr is the paraxial radius of curvature of the image side surface of the negative meniscus lens component in the second lens group,
It is. The said 1st lens group and the said negative meniscus lens component in the said 2nd lens group satisfy the following conditional expressions (3), The Claim 1 thru | or 22 characterized by the above-mentioned. Zoom lens.
−0.3 <f _2n / f ₁ <−0.13 (3)
However,
f _2n is a focal length of the negative meniscus lens in the second lens group,
f ₁ is the focal length of the first lens group,
It is. The zoom lens according to any one of claims 1 to 23, wherein the negative lens in the third lens group satisfies the following conditional expression (4).
1 <(R _3nf + R _3nr ) / (R _3nf −R _3nr ) <6 (4)
However,
R _3nf is the paraxial radius of curvature of the object side surface of the negative lens in the third lens group,
R _3nr is the paraxial radius of curvature of the image side surface of the negative lens in the third lens group,
It is. The zoom lens according to any one of claims 1 to 24, wherein the negative lens in the third lens group satisfies the following conditional expression (5).
15 <ν _3n <35 (5)
Where ν _3n is the Abbe number of the negative lens in the third lens group. The zoom lens according to any one of claims 1 to 25, wherein the positive lens and the negative lens in the third lens group satisfy the following conditional expression (6).
5 <ν _3p −ν _3n <70 (6)
However,
ν _3p is the Abbe number of the positive lens in the third lens group,
ν _3n is the Abbe number of the negative lens in the third lens group,
It is. 27. The zoom lens according to claim 1, wherein the following conditional expression (7) is satisfied.
4 <ft / fw (7)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
ft is the focal length of the entire zoom lens system at the telephoto end,
It is. A zoom lens,
An imaging element having an imaging surface disposed on the image side and converting an optical image on the imaging surface formed by the zoom lens into an electrical signal;
With
An image pickup apparatus, wherein the zoom lens is the zoom lens according to any one of claims 1 to 27. A signal processing circuit that processes image data obtained by imaging with the imaging element and outputs the image data as a changed shape;
29. The imaging apparatus according to claim 28, wherein the following conditional expression (8) is satisfied in a state where the zoom lens is focused at the wide-angle end and the farthest distance.
0.65 <y ₀₇ / (fw · tan ω _07w ) <0.99 (8)
However,
fw is the focal length of the entire zoom lens system at the wide-angle end,
When the distance to the farthest point from the center in the effective image pickup plane of the image pickup device and a y _10,
y ₀₇ = 0.7 × y ₁₀
If effective image pickup area changes at the telephoto end from the wide-angle end, y ₁₀ is the maximum value of the possible values,
ω _07w is an angle formed between the incident light beam and the optical axis in the object space of the principal ray incident on the image position where the image height is y ₀₇ from the center on the imaging surface at the wide angle end.

Images