JP2012255895A - Zoom lens and imaging apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an influence of various aberrations, in particular, an influence of a coma aberration when an F number is further reduced and the size of an optical system is reduced in a conventional optical system.SOLUTION: In the zoom lens has, in order from an object side, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power, a fourth lens group having positive refracting power, and a final lens group having positive refracting power, the first lens group is fixed, the second lens group is moved to the image surface side, the third lens group is fixed, and the fourth lens group is moved in varying magnification from a wide angle end to a telephoto end, and the fourth lens group is moved in focusing, and the following conditional expression is satisfied: (1) 0.20<log(β34T/β34 W)<0.9 logγ.

Description

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

  In moving image shooting, shooting is always performed while zooming or focusing. The fact that zooming and focusing are always performed means that the lens group of the optical system is constantly moving. When the lens group moves, a sliding sound is generated accordingly. If this sliding sound is loud, it will be recorded as noise. Therefore, a zoom lens with a small number of moving lens groups has been proposed.

  As an example of a zoom lens with fewer moving lens groups, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power And a fourth lens group having a positive refractive power. At the time of zooming from the wide-angle end to the telephoto end, the first lens group is fixed, the second lens group moves toward the image plane side, and the third lens group Has been fixed, and a zoom lens has been proposed in which the fourth lens group is moved, and the fourth lens group is further moved to perform focusing (Patent Documents 1 to 3).

  Further, a zoom lens has been proposed in which a fifth lens group (fixed group) having a positive refractive power is added to the image side of the fourth lens group. (Patent Documents 4 to 7).

Japanese Patent Laid-Open No. 62-178717 JP-A-62-29718 Japanese Unexamined Patent Publication No. 63-123209 JP-A-3-154014 JP-A-5-264902 JP-A-6-27375 Japanese Patent Laid-Open No. 7-151967

  In recent years, efforts have been actively made for high-definition imaging devices. In a conventional standard television system such as NTSC or PAL, the number of pixels required for the image sensor is 300,000 to 400,000 pixels. On the other hand, in the high vision system, the number of pixels required for the image sensor is 2 million pixels (1920 × 1080). For this reason, the image forming performance of the zoom lens is required to be commensurate with it.

  As an example, the zoom lens has an imaging performance such as an F value of 2 at the wide-angle end, an aspect ratio of 16: 9, a horizontal field angle of about 70 degrees (77 degrees diagonally), and a zoom ratio of more than 10 times. Required. Of course, it is also an essential condition to be small and light. However, there has not yet been proposed a zoom lens that can satisfy these conditions.

  The present invention has been made in view of the above, and is a compact lens having various aberrations satisfactorily corrected while being a zoom lens having a small F-number at the wide-angle end, a wide angle of view, and a high zoom ratio. It aims to provide a zoom lens.

In order to solve the above-described problems and achieve the object, the zoom lens of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, A third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a final lens group having a positive refractive power, and at the time of zooming from the wide angle end to the telephoto end, The lens group is fixed, the second lens group is moved to the image plane side, the third lens group is fixed, the fourth lens group is moved, and the fourth lens group is moved during focusing. (1) is satisfied.
0.20 <log (β34T / β34W) <0.9 · logγ (1)
However,
β34W is the magnification of the combined system of the third lens unit and the fourth lens unit at the wide-angle end,
β34T is the magnification of the combined system of the third lens unit and the fourth lens unit at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (2).
0.1 <| β2W | <0.30 (2)
However,
β2W is the magnification of the second lens group at the wide-angle end, and is the magnification when focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (3).
0.3 <log (β2T / β2W) / logγ <0.8 (3)
However,
β2W is the magnification of the second lens group at the wide-angle end,
β2T is the magnification of the second lens group at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is.

Moreover, according to a preferable aspect of the present invention, it is desirable that the following conditional expression (4) is satisfied.
0.30 <| β34W | <0.70 (4)
However,
β34W is a magnification of the combined system of the third lens unit and the fourth lens unit at the wide angle end, and is a magnification at the time of focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (5).
1.10 <f34W / f34T <2.00 (5)
However,
f34W is the focal length of the combined system of the third lens group and the fourth lens group at the wide-angle end,
f34T is the focal length of the combined system of the third lens group and the fourth lens group at the telephoto end,
Both are magnifications when focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (6).
-0.5 <fW / f123T <0.10 (6)
However,
fW is the focal length of the entire zoom lens system at the wide-angle end,
f123T is the focal length of the synthesis system from the first lens group to the third lens group at the telephoto end,
Both are focal lengths when focusing on an object point at infinity,
It is.

Moreover, according to a preferable aspect of the present invention, it is desirable that the following conditional expression (7) is satisfied.
9 <f1 / fW <18 (7)
However,
f1 is the focal length of the first lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (8).
-0.18 <f2 / f1 <-0.06 (8)
However,
f1 is the focal length of the first lens group,
f2 is the focal length of the second lens group,
It is.

Moreover, according to a preferable aspect of the present invention, it is desirable that the following conditional expression (9) is satisfied.
4.0 <f4 / fW <10.0 (9)
However,
f4 is the focal length of the fourth lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions (10).
-2.00 <ff4 / f4 <-1.00 (10)
However,
f4 is the focal length of the fourth lens group,
ff4 is the distance from the most object side surface top of the fourth lens group to the front focal position of the fourth lens group,
It is.

Further, according to a preferable aspect of the present invention, it is desirable that the fourth lens group includes a lens component having a positive refractive power and a lens component having a negative refractive power in order from the object side.
However,
The lens component is a single lens or a cemented lens and has two optical surfaces in contact with air.
It is.

Moreover, according to a preferable aspect of the present invention, it is desirable that the following conditional expression (11) is satisfied.
-0.3 <(R42F-R42R) / (R42F + R42R) <0.6 (11)
However,
R42F is the paraxial radius of curvature of the lens surface having the negative refractive power of the fourth lens unit on the most object side surface,
R42R is the paraxial radius of curvature of the most image side surface of the lens component having the negative refractive power of the fourth lens group,
It is.

According to a preferred aspect of the present invention, the lens component having a negative refractive power of the fourth lens group is a cemented lens, and the cemented lens includes a single lens having a positive refractive power and a negative refractive power in order from the object side. It is desirable to use a single lens and satisfy the following conditional expression (12).
-0.5 <(R422F + R422R) / (R422F-R422R) <1.2 (12)
However,
R422F is the paraxial radius of curvature of the object side surface of the single lens having the negative refractive power of the fourth lens group,
R422R is a paraxial radius of curvature of the image side surface of the single lens having a negative refractive power in the fourth lens group,
It is.

Moreover, according to a preferable aspect of the present invention, it is desirable that the following conditional expression (13) is satisfied.
0.50 <fb3 / f3 <1.5 (13)
However,
f3 is the focal length of the third lens group,
fb3 is the distance from the most image side surface top of the third lens group to the rear focal position of the third lens group,
It is.

According to a preferred aspect of the present invention, the third lens group is composed of two lens components, a lens component having a positive refractive power and a lens component having a negative refractive power, in order from the object side. It is desirable to satisfy (14).
0.1 <(R32F-R32R) / (R32F + R32R) <5.0 (14)
However,
R32F is the paraxial radius of curvature of the most object side surface of the lens component having the negative refractive power of the third lens unit,
R32R is the paraxial radius of curvature of the most image side surface of the lens component having the negative refractive power of the third lens unit,
The lens component is a single lens or a cemented lens and has two optical surfaces in contact with air.
It is.

According to a preferred aspect of the present invention, it is desirable that the final lens group is composed of a lens component having a positive refractive power.
However,
The lens component is a single lens or a cemented lens and has two optical surfaces in contact with air.
It is.

  According to another aspect of the present invention, there is provided an image pickup apparatus comprising the above zoom lens and an image pickup element disposed on an image plane of the zoom lens.

  According to the present invention, a zoom lens having a small F-number at the wide-angle end, a wide angle of view, and a high zoom ratio, and having various aberrations corrected favorably, and an image pickup apparatus using the same Can be provided.

It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 1 of this invention, Comprising: A wide angle end (a), an intermediate state (b), a telephoto end (c FIG. FIG. 3 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when focusing on an object point at infinity of the imaging optical system according to the first example, and illustrating a wide angle end. It is an aberration diagram in (a), intermediate state (b), telephoto end (c). It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 2 of this invention, Comprising: A wide angle end (a), an intermediate state (b), a telephoto end (c) FIG. FIG. 10 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when focusing on an object point at infinity of the image pickup optical system according to the second example, with a wide angle end; It is an aberration diagram in (a), intermediate state (b), telephoto end (c). It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 3 of this invention, Comprising: A wide angle end (a), an intermediate state (b), a telephoto end (c) FIG. FIG. 6 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when focusing on an object point at infinity of the imaging optical system according to the third example, and illustrating a wide angle end; It is an aberration diagram in (a), intermediate state (b), telephoto end (c). It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 4 of this invention, Comprising: A wide angle end (a), an intermediate state (b), a telephoto end (c) FIG. FIG. 6 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when focusing on an object point at infinity of the imaging optical system according to the fourth example, and at a wide angle end; It is an aberration diagram in (a), intermediate state (b), telephoto end (c). It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 5 of this invention, Comprising: A wide-angle end (a), an intermediate state (b), a telephoto end (c) FIG. FIG. 10 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when focusing on an object point at infinity of the imaging optical system according to the fifth example, and illustrating a wide angle end. It is an aberration diagram in (a), intermediate state (b), telephoto end (c). It is a front perspective view which shows the external appearance of the digital camera 40 incorporating the optical system by this invention. 2 is a rear perspective view of the digital camera 40. FIG. 2 is a cross-sectional view showing an optical configuration of a digital camera 40. FIG. 1 is a front perspective view of a state in which a cover of a personal computer 300 that is an example of an information processing apparatus in which an optical system of the present invention is incorporated as an objective optical system is opened. FIG. 2 is a cross-sectional view of a photographing optical system 303 of a personal computer 300. FIG. 2 is a side view of a personal computer 300. FIG. 1A and 1B are diagrams showing a mobile phone that is an example of an information processing apparatus in which the optical system of the present invention is built in as a photographing optical system. FIG. 3A is a front view of the mobile phone 400, FIG. 2 is a cross-sectional view of a photographing optical system 405. FIG.

  The zoom lens according to the embodiment will be described. A lens having a positive paraxial focal length is defined as a positive lens, and a lens having a negative paraxial focal length is defined as a negative lens.

The zoom lens of this embodiment includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens power. And a final lens group having a positive refractive power, the first lens group is fixed and the second lens group is an image at the time of zooming from the wide-angle end to the telephoto end. Moving to the surface side, the third lens group is fixed, the fourth lens group is moved, and the fourth lens group is moved during focusing, and the following conditional expression (1) is satisfied.
0.20 <log (β34T / β34W) <0.9 · logγ (1)
However,
β34W is the magnification of the combined system of the third lens unit and the fourth lens unit at the wide-angle end,
β34T is the magnification of the combined system of the third lens unit and the fourth lens unit at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is.

  In the zoom lens according to the present embodiment, the zoom lens includes at least five lens groups. Thereby, it is possible to realize a wide angle of view, a large aperture ratio, and a high zoom ratio of the optical system. Further, at the time of zooming from the wide-angle end to the telephoto end, only the second lens group and the fourth lens group are moved in the zoom lens according to the present embodiment. By doing so, the number of movable lens groups is minimized, and the weight of the movable lens groups is realized. Further, the fourth lens group has a role of focal position correction and focusing in addition to zooming. This minimizes the number of movable lens groups. In order to minimize the number of movable lens groups, the first lens group and the third lens group are fixed at any time during zooming, focal position correction, and focusing. The final lens group may be fixed at any time during zooming, focal position correction, and focusing, similarly to the first lens group and the third lens group.

  By the way, the conventional zoom lens has a configuration in which most of the zoom ratio is gained by moving the second lens group, and the fourth lens group mainly performs focus position correction and focusing. With such a configuration, it is extremely difficult to realize a zoom lens having a wide angle of view and a high zoom ratio (for example, a diagonal angle of view exceeding 75 degrees and a zoom ratio exceeding 10 times). Therefore, in the zoom lens according to the present embodiment, the zooming function is shared by the lens group located on the image side of the third lens group. By doing so, it is possible to increase the zoom ratio while widening (increasing) the angle of view. Further, when the angle of view is increased, it becomes difficult to correct aberrations in the first lens group and the second lens group, but this difficulty can be alleviated by adopting the configuration as described above.

  The configuration of each lens group is, for example, that the first lens group includes one negative lens, the second lens group includes one positive lens, and includes two lens components of the third lens group, and the fourth lens group. May consist of two lens components, and the final lens group may consist of one lens component.

  Furthermore, the zoom lens according to the present embodiment satisfies the conditional expression (1). By satisfying conditional expression (1), a zoom lens having a small F value at the wide-angle end, a wide angle of view, and a high zoom ratio can be realized.

  Conditional expression (1) defines the zoom ratio (magnification) of the synthesis system of the third lens group and the fourth lens group. By satisfying conditional expression (1), it is possible to widen the angle of view and increase the zoom ratio in a state where spherical aberration and coma aberration are satisfactorily corrected.

  When the upper limit of conditional expression (1) is exceeded, the difference in F value between the wide-angle end and the telephoto end increases, or the axial ray height increases at the telephoto end. When the axial ray height is high at the telephoto end, it becomes difficult to correct spherical aberration and coma. On the other hand, if the lower limit value of conditional expression (1) is not reached, zooming is performed only by moving the second lens group. In this case, the second lens group has to have a strong refractive power together with the first lens group. As a result, the light beam height at these lens groups becomes high, especially at the wide-angle end, making it difficult to widen the angle.

Here, it is preferable that the following conditional expression (1 ′) is satisfied instead of conditional expression (1).
0.30 <log (β34T / β34W) <0.7 · logγ (1 ')
Further, it is more preferable to satisfy the following conditional expression (1 ″) instead of conditional expression (1).
0.35 <log (β34T / β34W) <0.55 · logγ (1 ")
However,
γ = fT / fW> 9
It is.
Further, it is more preferable to satisfy the following conditional expression (1 ″ ′) instead of conditional expression (1).
0.38 <log (β34T / β34W) <0.5 · logγ (1 "')
However,
γ = fT / fW> 10
It is.

  The zoom ratio γ (= fT / fW) is preferably 9 or more, and more preferably 10 or more.

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (2).
0.1 <| β2W | <0.30 (2)
However,
β2W is the magnification of the second lens group at the wide-angle end, and is the magnification when focusing on an object point at infinity,
It is.

  Conditional expression (2) defines the magnification of the second lens group at the wide-angle end (when focusing on an object point at infinity). If the magnification of the second lens group at the wide angle end is set to a small value, the absolute value of the magnification at the telephoto end of the second lens group does not greatly exceed 1. Therefore, it is easy to perform multiplication by the synthesis system using the third lens group and the fourth lens group. As a result, it becomes easy to satisfy the conditional expression (1). Also, the focal length of the first lens group is naturally longer. This facilitates correction of off-axis aberrations at the wide-angle end and aberrations from the on-axis to the entire off-axis at the telephoto end. On the other hand, when the magnification at the wide-angle end of the second lens group is further reduced and becomes extremely zero, that is, when there is no power in the first lens group, the second lens group has no zooming effect ( In other words, it becomes a negative leading zoom lens). This makes it difficult to secure a high zoom ratio, and it is not preferable to make the magnification at the wide angle end of the second lens group too small. Therefore, by satisfying conditional expression (2), a high zoom ratio can be obtained with the off-axis aberration being corrected well.

  Exceeding the upper limit of conditional expression (2) makes correction of off-axis aberrations particularly difficult when the angle of view is widened. On the other hand, if the lower limit of conditional expression (2) is not reached, it is difficult to ensure a high zoom ratio.

Here, it is preferable that the following conditional expression (2 ′) is satisfied instead of conditional expression (2).
0.1 <| β2W | <0.24 (2 ′)
Further, it is more preferable that the following conditional expression (2 ″) is satisfied instead of conditional expression (2).
0.1 <| β2W | <0.22 (2 ″)

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (3).
0.3 <log (β2T / β2W) / logγ <0.8 (3)
However,
β2W is the magnification of the second lens group at the wide-angle end,
β2T is the magnification of the second lens group at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is.

  Conditional expression (3) defines the zoom ratio (magnification) of the second lens group with respect to the zoom ratio of the entire zoom lens system. Conditional expression (3) is a condition for suppressing the multiplication action of the second lens group so that the absolute value of the magnification at the telephoto end of the second lens group does not greatly exceed 1. Satisfying conditional expression (3) makes it possible to correct spherical aberration and coma and to widen the angle.

  If the upper limit of conditional expression (3) is exceeded, zooming will be performed only by moving the second lens group. In this case, the second lens group has to have a strong refractive power together with the first lens group. Then, especially at the wide-angle end, the height of light rays in these lens groups becomes high, and it is difficult to widen the angle. On the other hand, if the lower limit value of conditional expression (3) is not reached, the difference in F value between the wide-angle end and the telephoto end increases or the axial ray height increases at the telephoto end. When the axial ray height is high at the telephoto end, it becomes difficult to correct spherical aberration and coma.

Here, it is preferable that the following conditional expression (3 ′) is satisfied instead of conditional expression (3).
0.45 <log (β2T / β2W) / logγ <0.67 (3 ′)
Further, it is more preferable that the following conditional expression (3 ″) is satisfied instead of conditional expression (3).
0.50 <log (β2T / β2W) / logγ <0.64 (3 ″)

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (4).
0.30 <| β34W | <0.70 (4)
However,
β34W is a magnification of the combined system of the third lens unit and the fourth lens unit at the wide angle end, and is a magnification at the time of focusing on an object point at infinity,
It is.

  Conditional expression (4) defines the magnification of the combined system of the third lens group and the fourth lens group at the wide-angle end. When the conditional expression (4) is satisfied, the zoom lens can have a wider angle of view and a thinner thickness.

  If the upper limit of conditional expression (4) is exceeded, it is necessary to shorten the focal length of the first lens group. Then, it becomes difficult to widen the angle of view. On the other hand, if the lower limit value of conditional expression (4) is not reached, the fourth lens group and the adjacent image-side lens group tend to interfere with each other. If the distance between the two is increased to prevent interference, the overall length of the optical system becomes longer.

Here, it is preferable to satisfy the following conditional expression (4 ′) instead of conditional expression (4).
0.36 <| β34W | <0.56 (4 ′)
It is more preferable to satisfy the following conditional expression (4 ″) instead of conditional expression (4).
0.39 <| β34W | <0.53 (4 ″)

Moreover, it is preferable that the zoom lens according to the present embodiment satisfies the following conditional expression (5).
1.10 <f34W / f34T <2.00 (5)
However,
f34W is the focal length of the combined system of the third lens group and the fourth lens group at the wide-angle end,
f34T is the focal length of the combined system of the third lens group and the fourth lens group at the telephoto end,
Both are focal lengths when focusing on an object point at infinity,
It is.

  Conditional expression (5) defines the ratio of the focal length at the wide angle end to the focal length at the telephoto end of the synthesis system of the third lens group and the fourth lens group. By satisfying conditional expression (5), the focal length of the synthesis system can be maintained or shortened when zooming from the wide-angle end to the telephoto end. As a result, since the zoom ratio (magnification) by the synthesis system of the third lens group and the fourth lens group can be increased, the zoom ratio of the entire zoom lens system can be increased.

  If the upper limit value of conditional expression (5) is exceeded, the relative decentration sensitivity between the third lens group and the fourth lens group becomes high, and in particular, spherical aberration and coma aberration deteriorate. Therefore, the imaging performance is likely to be deteriorated. On the other hand, if the lower limit value of conditional expression (5) is not reached, even if the movement amount of the fourth lens group is increased, the zoom ratio (magnification) by the synthesis system of the third lens group and the fourth lens group is increased. It becomes difficult to do.

Here, it is preferable that the following conditional expression (5 ′) is satisfied instead of conditional expression (5).
1.20 <f34W / f34T <2.00 (5 ')
Further, it is more preferable that the following conditional expression (5 ″) is satisfied instead of conditional expression (5).
1.25 <f34W / f34T <2.00 (5 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (6).
-0.5 <fW / f123T <0.10 (6)
However,
fW is the focal length of the entire zoom lens system at the wide-angle end,
f123T is the focal length of the synthesis system from the first lens group to the third lens group at the telephoto end,
Both are focal lengths when focusing on an object point at infinity,
It is.

  Conditional expression (6) defines the ratio of the focal length of the combined zoom lens system from the first lens group to the third lens group at the telephoto end and the entire zoom lens system at the wide angle end. By satisfying conditional expression (6), the occurrence of various aberrations can be suppressed with a high zoom ratio.

  Exceeding the upper limit of conditional expression (6) is disadvantageous for widening the angle, correcting meridional field curvature and coma at the wide-angle end, and correcting axial chromatic aberration and spherical aberration at the telephoto end. On the other hand, if the lower limit of conditional expression (6) is not reached, it will be disadvantageous for increasing the zoom ratio.

Here, it is preferable to satisfy the following conditional expression (6 ′) instead of conditional expression (6).
-0.4 <fW / f123T <0.04 (6 ')
It is more preferable to satisfy the following conditional expression (6 ″) instead of conditional expression (6).
-0.3 <fW / f123T <0.02 (6 ")

In the zoom lens according to the present embodiment, it is preferable that the following conditional expression (7) is satisfied.
9 <f1 / fW <18 (7)
However,
f1 is the focal length of the first lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is.

  Conditional expression (7) defines the ratio of the distance between the first lens group and the entire zoom lens system at the wide-angle end. By satisfying conditional expression (7), the occurrence of various aberrations can be suppressed with a high zoom ratio.

  Exceeding the upper limit value of conditional expression (7) is disadvantageous for increasing the zoom ratio. On the other hand, if the lower limit value of conditional expression (7) is not reached, widening the angle of view, correcting meridional field curvature and coma at the wide-angle end, and correcting axial chromatic aberration and spherical aberration at the telephoto end are good. It becomes difficult.

Here, it is preferable that the following conditional expression (7 ′) is satisfied instead of conditional expression (7).
10.5 <f1 / fW <17 (7 ')
Further, it is more preferable to satisfy the following conditional expression (7 ″) instead of conditional expression (7).
11.5 <f1 / fW <16 (7 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (8).
-0.18 <f2 / f1 <-0.06 (8)
However,
f1 is the focal length of the first lens group,
f2 is the focal length of the second lens group,
It is.

  Conditional expression (8) defines the ratio of the focal length of the first lens group and the focal length of the second lens group, and is a condition for obtaining a high zoom ratio while widening the angle.

  If the upper limit value of conditional expression (8) is exceeded, it becomes difficult to widen the angle. On the other hand, if the lower limit of conditional expression (8) is not reached, it will be difficult to increase the zoom ratio.

Here, it is preferable that the following conditional expression (8 ′) is satisfied instead of conditional expression (8).
-0.16 <f2 / f1 <-0.06 (8 ')
Further, it is more preferable that the following conditional expression (8 ″) is satisfied instead of conditional expression (8).
-0.15 <f2 / f1 <-0.06 (8 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (9).
4.0 <f4 / fW <10.0 (9)
However,
f4 is the focal length of the fourth lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is.

  Conditional expression (9) defines the ratio of the focal lengths of the fourth lens group and the entire zoom lens system at the wide-angle end. By satisfying conditional expression (9), it is thin and the occurrence of aberration due to decentration can be suppressed.

  If the upper limit value of conditional expression (9) is exceeded, the focal length of the fourth lens group becomes longer, and the amount of movement of the fourth lens group during zooming and focusing increases. On the other hand, if the lower limit value of conditional expression (9) is not reached, aberration fluctuations due to zooming and decentration sensitivity tend to increase. As a result, spherical aberration and coma are particularly deteriorated.

Here, it is preferable that the following conditional expression (9 ′) is satisfied instead of conditional expression (9).
4.8 <f4 / fW <7.0 (9 ')
Further, it is more preferable that the following conditional expression (9 ″) is satisfied instead of conditional expression (9).
5.1 <f4 / fW <6.0 (9 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (10).
-2.00 <ff4 / f4 <-1.00 (10)
However,
f4 is the focal length of the fourth lens group,
ff4 is the distance from the most object side surface top of the fourth lens group to the front focal position of the fourth lens group,
It is.

  Conditional expression (10) defines the ratio of the distance from the most object-side surface top of the fourth lens group and the fourth lens group to the front focal position of the fourth lens group. By satisfying conditional expression (10), the optical system can be made thin, and the occurrence of off-axis aberrations can be suppressed.

  When the upper limit value of conditional expression (10) is exceeded, the third lens group and the fourth lens group are likely to approach each other. In this case, it is difficult to secure a focusing space at the telephoto end of the fourth lens group. On the other hand, if the lower limit value of conditional expression (10) is not reached, the off-axis ray height in the fourth lens group becomes particularly high, and it becomes difficult to correct off-axis aberrations.

Here, it is preferable that the following conditional expression (10 ′) is satisfied instead of conditional expression (10).
-1.50 <ff4 / f4 <-1.10. (10 ')
Further, it is more preferable that the following conditional expression (10 ″) is satisfied instead of conditional expression (10).
-1.35 <ff4 / f4 <-1.15 (10 ")

  In the zoom lens according to the present embodiment, it is preferable that the moving direction of the fourth lens unit is always on the object side during zooming.

  This increases the multiplication effect in the synthesis system of the third lens group and the fourth lens group. Therefore, the zooming efficiency in the entire zoom lens system can be increased. In particular, it is effective when zooming toward the telephoto end while maintaining the focused state on the object. The order of focusing and zooming may be arbitrary, and both may be performed simultaneously or in parallel.

  In the zoom lens according to the present embodiment, it is preferable that the fourth lens group includes a lens component having a positive refractive power and a lens component having a negative refractive power in order from the object side.

  In this way, the principal point position of the fourth lens group can be located on the object side. Thereby, at the telephoto end where the amount of extension is the largest, the distance from the third lens group can be widened in advance. As a result, focusing on an object at a shorter distance can be performed by extending the fourth lens group toward the object side. The lens component is a single lens or a cemented lens and has two optical surfaces that come into contact with air.

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (11).
-0.3 <(R42F-R42R) / (R42F + R42R) <0.6 (11)
However,
R42F is the paraxial radius of curvature of the lens surface having the negative refractive power of the fourth lens unit on the most object side surface,
R42R is the paraxial radius of curvature of the most image side surface of the lens component having the negative refractive power of the fourth lens group,
It is.

  Conditional expression (11) defines the shape of the negative lens component of the fourth lens group (indicated by the reciprocal of the shape factor). By satisfying conditional expression (11), occurrence of coma and curvature of field can be suppressed.

  If the upper limit of conditional expression (11) is exceeded, correction of spherical aberration, coma aberration, and meridional field curvature tends to be difficult. On the other hand, if the lower limit of conditional expression (11) is not reached, it is difficult to position the principal point position of the fourth lens group toward the object side. In this case, it is difficult to secure a space for the fourth lens group to move for focusing at the telephoto end. As a result, it is difficult to shorten the overall length of the optical system.

Here, it is preferable that the following conditional expression (11 ′) is satisfied instead of conditional expression (11).
−0.2 <(R42F−R42R) / (R42F + R42R) <0.4 (11 ′)
Further, it is more preferable that the following conditional expression (11 ″) is satisfied instead of conditional expression (11).
-0.1 <(R42F-R42R) / (R42F + R42R) <0.2 (11 ")

In the zoom lens according to the present embodiment, the lens component having negative refractive power in the fourth lens group is a cemented lens. The cemented lens includes a single lens having positive refractive power and a single lens having negative refractive power in order from the object side. It is preferable that the lens satisfies the following conditional expression (12).
-0.5 <(R422F + R422R) / (R422F-R422R) <1.2 (12)
However,
R422F is the paraxial radius of curvature of the object side surface of the single lens having the negative refractive power of the fourth lens group,
R422R is a paraxial radius of curvature of the image side surface of the single lens having a negative refractive power in the fourth lens group,
It is.

  Conditional expression (12) defines the shape of the negative lens (indicated by the reciprocal of the shape factor) constituting the cemented lens of the fourth lens group. By satisfying conditional expression (12), the occurrence of coma and field curvature can be suppressed.

  When the upper limit of conditional expression (12) is exceeded, correction of coma aberration and meridional field curvature tends to be difficult. On the other hand, if the lower limit of conditional expression (12) is not reached, it will be difficult to position the principal point position of the fourth lens group toward the object side. In this case, it is difficult to secure a space for the fourth lens group to move for focusing at the telephoto end. As a result, it is difficult to shorten the overall length of the optical system.

Here, it is preferable that the following conditional expression (12 ′) is satisfied instead of conditional expression (12).
−0.2 <(R422F + R422R) / (R422F−R422R) <0.6 (12 ′)
It is more preferable to satisfy the following conditional expression (12 ″) instead of conditional expression (12).
-0.1 <(R422F + R422R) / (R422F-R422R) <0.4 (12 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (13).
0.50 <fb3 / f3 <1.5 (13)
However,
f3 is the focal length of the third lens group,
fb3 is the distance from the most image side surface top of the third lens group to the rear focal position of the third lens group,
It is.

  Conditional expression (13) defines the ratio of the distance from the most image-side surface top of the third lens group and the third lens group to the front focal position of the third lens group. By satisfying conditional expression (13), it is possible to suppress the occurrence of off-axis aberration with a thin shape.

  Exceeding the upper limit of conditional expression (13) is disadvantageous for shortening the overall length of the zoom lens. On the other hand, when the lower limit value of conditional expression (13) is not reached, coma aberration tends to deteriorate.

Here, it is preferable to satisfy the following conditional expression (13 ′) instead of conditional expression (13).
0.72 <fb3 / f3 <1.1 (13 ')
It is more preferable to satisfy the following conditional expression (13 ″) instead of conditional expression (13).
0.82 <fb3 / f3 <1.0 (13 ")

  In the zoom lens according to the present embodiment, it is preferable that the third lens group includes, in order from the object side, two lens components, a lens component having a positive refractive power and a lens component having a negative refractive power.

  In this way, the principal point position of the fourth lens group can be positioned toward the object side. As a result, the overall length of the zoom lens can be shortened. The lens component is a single lens or a cemented lens and has two optical surfaces that come into contact with air.

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (14).
0.1 <(R32F-R32R) / (R32F + R32R) <5.0 (14)
However,
R32F is the paraxial radius of curvature of the most object side surface of the lens component having the negative refractive power of the third lens unit,
R32R is the paraxial radius of curvature of the most image side surface of the lens component having the negative refractive power of the third lens unit,
It is.

  Conditional expression (14) defines the shape of the lens component having the negative refractive power of the third lens group (indicated by the reciprocal of the shape factor). By satisfying conditional expression (14), the overall length of the zoom lens can be shortened.

  Exceeding the upper limit of conditional expression (14) is advantageous for shortening the entire length, but it is difficult to correct spherical aberration and coma over the entire zoom range. On the other hand, if the lower limit value of conditional expression (14) is not reached, it is difficult to position the principal point position of the third lens group toward the object side, so it is difficult to shorten the overall length of the zoom lens.

Here, it is preferable that the following conditional expression (14 ′) is satisfied instead of conditional expression (14).
0.2 <(R32F-R32R) / (R32F + R32R) <2.5 (14 ')
Further, it is more preferable that the following conditional expression (14 ″) is satisfied instead of conditional expression (14).
0.4 <(R32F-R32R) / (R32F + R32R) <1.2 (14 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (15).
0.7 <| β2T | <2.0 (15)
However,
β2T is the magnification of the second lens group at the telephoto end, and is the magnification when focusing on an object point at infinity,
It is.

  Conditional expression (15) defines the magnification of the second lens group at the telephoto end (when focusing on an object point at infinity). Regarding the magnification of the second lens unit at the telephoto end (when focusing on an object point at infinity), it is preferable not to greatly exceed | −1 |, that is, satisfy the conditional expression (15). By doing so, it is possible to increase the magnification (multiplication) rate by the synthesis system of the third lens group and the fourth lens group.

  If the upper limit value of conditional expression (15) is exceeded, the magnification ratio of the synthesis system of the third lens group and the fourth lens group becomes small. As a result, it becomes difficult to obtain a high zoom ratio. On the other hand, if the lower limit of conditional expression (15) is not reached, the zoom ratio in the second lens group will be small. In this case, it is necessary to increase the zoom ratio in the synthesis system of the third lens group and the fourth lens group. Then, at the telephoto end, it becomes difficult to secure a space for the fourth lens group to move for focusing. Here, if it is attempted to forcibly secure the movement space, it becomes difficult to reduce the total length and correct each aberration variation due to focusing.

  The image point P by the second lens group is an object point with respect to the synthesis system of the third lens group and the fourth lens group. As the magnification of the second lens group greatly exceeds | −1 | as the distance from the telephoto end increases, that is, when the conditional expression (15) is not satisfied, the image point P moves to the object side. Therefore, the magnification (when focusing on an object point at infinity) of the synthesis system of the third lens group and the fourth lens group becomes small.

Here, it is preferable that the following conditional expression (15 ′) is satisfied instead of conditional expression (15).
0.7 <| β2T | <1.4 (15 ′)
Further, it is more preferable that the following conditional expression (15 ″) is satisfied instead of conditional expression (15).
0.7 <| β2T | <1.2 (15 ")

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (16).
0.90 <| β34T | <1.80 (16)
However,
β34T is the magnification of the combined system of the third lens unit and the fourth lens unit at the telephoto end, and is the magnification at the time of focusing on an object point at infinity,
It is.

  Conditional expression (16) defines the magnification of the synthesis system of the third lens group and the fourth lens group at the telephoto end. By satisfying conditional expression (16), it is possible to widen the angle of view and reduce the thickness.

  If the upper limit of conditional expression (16) is exceeded, the F value at the telephoto end tends to increase. On the other hand, if the lower limit value of conditional expression (16) is not reached, the magnification β2W (at the time of focusing on an object point at infinity) of the second lens group at the wide angle end becomes too small. For this reason, it is difficult to increase the zoom ratio (magnification) as the entire zoom lens system.

Here, it is preferable that the following conditional expression (16 ′) is satisfied instead of conditional expression (16).
1.00 <| β34T | <1.35 (16 ′)
Further, it is more preferable that the following conditional expression (16 ″) is satisfied instead of conditional expression (16).
1.04 <| β34T | <1.28 (16 ″)

  In the zoom lens according to the present embodiment, it is preferable that the final lens group includes a lens component having a positive refractive power.

  The zoom lens system can be completed from the first lens group to the fourth lens group. However, the zoom lens having a wide angle and high magnification as in the present embodiment has a longer focal length of the first lens group. Since the appropriate magnification range of the zooming and focal position correction lens group from the second lens group to the fourth lens group tends to be slightly higher, a lens for reducing the overall magnification in order to obtain a desired focal length A group is needed. Therefore, in the zoom lens according to the present embodiment, the final lens group is provided on the image side of the fourth lens group, which is set to have a positive refractive power so as to have a magnification of less than +1. The lens component is a single lens or a cemented lens and has two optical surfaces that come into contact with air.

The zoom lens according to the present embodiment preferably satisfies the following conditional expression (17).
0.70 <| βFW | <0.98 (17)
However,
βFW is the magnification of the final lens group at the wide-angle end, and the magnification at the time of focusing on an object point at infinity,
It is.

  Conditional expression (17) defines the magnification of the final lens group at the wide-angle end. By satisfying conditional expression (17), it is possible to suppress the occurrence of various off-axis aberrations.

  If the upper limit value of conditional expression (17) is exceeded, it will be difficult to obtain a zoom lens having a wide angle and a high zoom ratio. On the other hand, if the lower limit value of conditional expression (17) is not reached, the refractive power of the final lens group becomes large, and therefore the off-axis ray height passing through the final lens group tends to increase. As a result, it is difficult to correct each off-axis aberration.

Here, it is preferable that the following conditional expression (17 ′) is satisfied instead of conditional expression (17).
0.73 <| βFW | <0.94 (17 ')
It is more preferable to satisfy the following conditional expression (17 ″) instead of conditional expression (17).
0.76 <| βFW | <0.90 (17 ")

  Further, if the final lens unit is moved toward the object side when zooming from the wide-angle end to the telephoto end, it is advantageous because it has the effect of canceling the meridional field curvature and coma variation during zooming. However, when the final lens group is moved toward the object side, error sensitivity such as decentration tends to increase especially near the telephoto end. Considering that the error sensitivity increases by making the final lens group movable, the final lens group should be fixed at the time of zooming.

  In addition, an imaging apparatus according to the present embodiment includes the zoom lens described above and an imaging element arranged on the image plane of the zoom lens.

  Hereinafter, embodiments of an imaging optical system and an imaging apparatus will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the positive / negative of the refractive power is based on the paraxial radius of curvature.

  Next, the image pickup optical system according to the first embodiment will be described. FIG. 1 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the first embodiment when focusing on an object point at infinity, and includes a wide-angle end (a), an intermediate state (b), and a telephoto end (c FIG.

  FIG. 2 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to the example 1 is focused on an object point at infinity. FIG. 6 is an aberration diagram at a wide-angle end (a), an intermediate state (b), and a telephoto end (c). FIY represents the image height. The symbols in the aberration diagrams are the same in the examples described later.

  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, The third lens group G3 has a positive refractive power, the fourth lens group G4 has a positive refractive power, and the fifth lens group G5 has a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the third lens group G3 is fixed, and the fourth lens group G4 is moved to the object side. The fifth lens group G5 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 directed toward the object side, a positive meniscus lens having a convex surface directed toward the object side, and a positive meniscus lens having a convex surface directed toward the object side. . The second lens group G2 includes a negative meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the image side, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fifth lens group G5 is composed of a biconvex positive lens.

  An aspherical surface is an image of both surfaces of a negative meniscus lens having a convex surface facing the image side of the second lens group G2, both surfaces of a biconvex positive lens of the third lens group G3, and a biconvex positive lens of the fifth lens group G5. It is used for five of the side surfaces.

  Next, an imaging optical system according to Example 2 will be described. FIG. 3 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the second embodiment when focusing on an object point at infinity, and includes a wide-angle end (a), an intermediate state (b), and a telephoto end (c FIG.

  FIG. 4 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to the example 2 is focused on an object point at infinity. FIG. 6 is an aberration diagram at a wide-angle end (a), an intermediate state (b), and a telephoto end (c).

  As shown in FIG. 3, 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, The third lens group G3 has a positive refractive power, the fourth lens group G4 has a positive refractive power, and the fifth lens group G5 has a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the third lens group G3 is fixed, and the fourth lens group G4 is moved to the object side. The fifth lens group G5 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 directed toward the object side and a biconvex positive lens, and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a negative meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fifth lens group G5 is composed of a biconvex positive lens.

  The aspherical surface includes both surfaces of a negative meniscus lens (second from the object side) with the convex surface facing the object side of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, and the fifth lens group G5. Are used on both sides of the double convex positive lens.

  Next, an imaging optical system according to Example 3 will be described. FIG. 5 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the third embodiment when focusing on an object point at infinity, and includes a wide angle end (a), an intermediate state (b), and a telephoto end (c). FIG.

  FIG. 6 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to the example 3 is focused on an object point at infinity. FIG. 6 is an aberration diagram at a wide-angle end (a), an intermediate state (b), and a telephoto end (c).

  As shown in FIG. 5, 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, The third lens group G3 has a positive refractive power, the fourth lens group G4 has a positive refractive power, and the fifth lens group G5 has a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the third lens group G3 is fixed, and the fourth lens group G4 is moved to the object side. The fifth lens group G5 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 directed toward the object side and a biconvex positive lens, and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a negative meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fifth lens group G5 is composed of a positive meniscus lens having a convex surface directed toward the object side.

  The aspherical surface includes both surfaces of a negative meniscus lens (second from the object side) with the convex surface facing the object side of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, and the fifth lens group G5. Are used on six surfaces of a positive meniscus lens having a convex surface facing the object side.

  Next, an imaging optical system according to Example 4 will be described. FIG. 7 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the fourth embodiment when focusing on an object point at infinity, and includes a wide-angle end (a), an intermediate state (b), and a telephoto end (c FIG.

  FIG. 8 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to the example 4 is focused on an object point at infinity. FIG. 6 is an aberration diagram at a wide-angle end (a), an intermediate state (b), and a telephoto end (c).

  As shown in FIG. 7, 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, The third lens group G3 has a positive refractive power, the fourth lens group G4 has a positive refractive power, and the fifth lens group G5 has a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the third lens group G3 is fixed, and the fourth lens group G4 is moved to the object side. The fifth lens group G5 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 directed toward the object side, a positive meniscus lens having a convex surface directed toward the object side, and a positive meniscus lens having a convex surface directed toward the object side. . The second lens group G2 includes a negative meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fifth lens group G5 is composed of a positive meniscus lens having a convex surface directed toward the image side.

  The aspherical surface includes both surfaces of a negative meniscus lens (second from the object side) with the convex surface facing the object side of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, and the fifth lens group G5. Are used on the six surfaces of the positive meniscus lens having a convex surface facing the image side.

  Next, an imaging optical system according to Example 5 will be described. FIG. 9 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the fifth embodiment at the time of focusing on an object point at infinity. FIG.

  FIG. 10 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to Example 5 is focused on an object point at infinity. FIG. 6 is an aberration diagram at a wide-angle end (a), an intermediate state (b), and a telephoto end (c).

  As shown in FIG. 9, 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, The third lens group G3 has a positive refractive power, the fourth lens group G4 has a positive refractive power, and the fifth lens group G5 has a positive refractive power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image side, the third lens group G3 is fixed, and the fourth lens group G4 is moved to the object side. The fifth lens group G5 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 directed toward the object side, a positive meniscus lens having a convex surface directed toward the object side, and a positive meniscus lens having a convex surface directed toward the object side. . The second lens group G2 includes a negative meniscus lens having a convex surface directed toward the object side, a negative meniscus lens having a convex surface directed toward the object side, and a cemented lens of a biconcave negative lens and a biconvex positive lens. The third lens group G3 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The fourth lens group G4 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The fifth lens group G5 is composed of a positive meniscus lens having a convex surface directed toward the image side.

  The aspherical surface includes both surfaces of a negative meniscus lens (second from the object side) with the convex surface facing the object side of the second lens group G2, both surfaces of the biconvex positive lens of the third lens group G3, and the fifth lens group G5. Are used on the six surfaces of the positive meniscus lens having a convex surface facing the image side.

  Next, numerical data of optical members constituting the imaging optical system of each of the above embodiments will be listed. In the numerical data of each embodiment, r1, r2,... Are the curvature radii of the lens surfaces, d1, d2,... Are the thickness or air interval of each lens, nd1, nd2,. Is the Abbe number of each lens, * is an aspheric surface, FL is the focal length of the entire system, Fno is the F number, ω is the half field angle, and BF is the back focus. .

The aspherical shape is expressed by the following equation when the optical axis direction is z, the direction orthogonal to the optical axis is y, the conical coefficient is K, and the aspherical coefficients are A4, A6, A8, and A10. .
z = (y ² / r) / [1+ {1− (1 + K) (y / r) ² } ^1/2 ]
+ A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰
E represents a power of 10. The symbols of these specification values are common to the numerical data of the examples described later.

Numerical example 1
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 52.1523 1.3000 1.84666 23.78
2 32.6000 9.3000 1.49700 81.55
3 600.0000 0.1500
4 32.8220 5.6000 1.72916 54.68
5 110.0000 Variable
6 150.0000 1.1000 1.77250 49.62
7 6.8228 4.6938
8 * -17.6865 1.1000 1.53368 55.90
9 * -200.0000 0.3922
10 -27.0451 1.0000 1.59282 68.62
11 28.3556 2.5000 1.94594 17.98
12 -81.3172 Variable
13 (Aperture) ∞ 0.7000
14 * 11.6202 3.2000 1.53368 55.90
15 * -19.7300 0.2000
16 35.8407 0.7000 1.84666 23.78
17 12.8354 Variable
18 22.9800 3.4000 1.76200 40.26
19 -37.4988 0.1500
20 13.6117 3.9000 1.58313 59.37
21 -24.5294 0.7000 1.80518 25.43
22 12.9572 Variable
23 21.2494 2.0000 1.53368 55.90
24 * -36.3228 2.7000
25 ∞ 1.0000 1.51633 64.14
26 ∞ 0.3000
27 ∞ 0.7000 1.51633 64.14
28 ∞ 0.4964
Image plane (imaging plane) ∞

Aspheric data 8th surface
K = 0.
A2 = 0.0000E + 00, A4 = -1.3796E-04, A6 = -3.4249E-06, A8 = 7.1817E-10, A10 = 0.0000E + 00

9th page
K = 0.
A2 = 0.0000E + 00, A4 = -2.7228E-04, A6 = -4.6717E-06, A8 = 3.7336E-08, A10 = 0.0000E + 00

14th page
K = 0.
A2 = 0.0000E + 00, A4 = -1.1404E-04, A6 = -1.0637E-06, A8 = 5.9473E-10, A10 = 0.0000E + 00

15th page
K = 0.
A2 = 0.0000E + 00, A4 = 7.6388E-05, A6 = -9.1278E-07, A8 = 0.0000E + 00, A10 = 0.0000E + 00

24th page
K = 0.
A2 = 0.0000E + 00, A4 = 2.9911E-04, A6 = -9.6034E-08, A8 = 0.0000E + 00, A10 = 0.0000E + 00

Various data
Wide angle Medium telephoto
FL 4.14288 13.93198 47.01961
Fno 1.8316 2.2580 2.8447
ω 37.7 11.9 3.5
Image height 3.00 3.00 3.00
Total lens length 97.3953 97.4000 97.4076
BF 0.49641 0.50000 0.50862

d5 0.70000 17.80941 27.17715
d12 28.27700 11.17465 1.79985
d17 19.16483 12.60927 6.80540
d22 1.97117 8.52073 14.33060

Zoom lens group data
G Start surface Focal length
1 1 49.37862
2 6 -7.14877
3 13 28.58517
4 18 22.70166
5 23 25.42808

Numerical example 2
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 64.1556 1.2000 1.84666 23.78
2 37.0904 8.4716 1.49700 81.55
3 -1162.2792 0.1500
4 34.0187 5.0784 1.72916 54.68
5 101.4155 Variable
6 297.4979 1.1000 1.72916 54.68
7 7.7542 3.4141
8 * 37.4496 1.1000 1.53368 55.90
9 * 18.3906 2.1481
10 -13.3282 1.0000 1.59282 68.62
11 39.5370 2.2000 1.94594 17.98
12 -52.4756 Variable
13 (Aperture) ∞ 0.7000
14 * 13.7419 3.2000 1.53368 55.90
15 * -16.6667 0.2000
16 646.8277 0.7000 1.84666 23.78
17 21.5938 Variable
18 21.0176 3.4000 1.76200 40.10
19 -32.7582 0.1500
20 15.6826 3.9000 1.56883 56.36
21 -15.6029 0.7000 1.80518 25.43
22 15.0481 Variable
23 * 593.4730 2.0000 1.53368 55.90
24 * -15.3902 2.2000
25 ∞ 1.0000 1.51633 64.14
26 ∞ 0.3000
27 ∞ 0.7000 1.51633 64.14
28 ∞ 0.5213
Image plane (imaging plane) ∞

Aspheric data 8th surface
K = 0.
A2 = 0.0000E + 00, A4 = -4.2882E-04, A6 = 7.7927E-06, A8 = -1.3054E-08, A10 = 0.0000E + 00

9th page
K = 0.
A2 = 0.0000E + 00, A4 = -6.0362E-04, A6 = 8.9092E-06, A8 = -3.8039E-08, A10 = 0.0000E + 00

14th page
K = 0.
A2 = 0.0000E + 00, A4 = -9.1865E-05, A6 = 1.0809E-07, A8 = 0.0000E + 00, A10 = 0.0000E + 00

15th page
K = 0.
A2 = 0.0000E + 00, A4 = 8.8658E-05, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

23rd page
K = 0.
A2 = 0.0000E + 00, A4 = -4.9854E-04, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

24th page
K = 0.
A2 = 0.0000E + 00, A4 = -2.6516E-05, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

Various data
Wide angle Medium telephoto
FL 4.01483 13.53981 45.78194
Fno 1.8351 2.3179 2.8306
ω 38.4 12.2 3.6
Image height 3.00 3.00 3.00
Total lens length 98.2775 98.2500 98.2812
BF 0.52132 0.52000 0.52503

d5 0.70000 19.77901 29.92741
d12 31.02700 11.94178 1.79959
d17 18.78297 12.69713 6.30809
d22 2.23403 8.29987 14.70891

Zoom lens group data
G Start surface Focal length
1 1 53.77399
2 6 -7.46979
3 13 28.58499
4 18 22.06881
5 23 28.14104

Numerical Example 3
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 63.5683 1.2000 1.84666 23.78
2 37.1184 8.8000 1.49700 81.61
3 -1121.9823 0.1500
4 33.7332 5.2000 1.72916 54.68
5 96.3714 Variable
6 296.0130 1.1000 1.72916 54.68
7 7.4617 3.4724
8 * 38.0001 1.1000 1.53368 55.90
9 * 19.3797 2.0528
10 -13.4317 1.0000 1.59282 68.63
11 39.8641 2.2000 1.94595 17.98
12 -52.1009 Variable
13 (Aperture) ∞ 0.7000
14 * 14.2090 3.2000 1.53368 55.90
15 * -16.1843 0.2000
16 336.2294 0.7000 1.84666 23.78
17 21.0247 Variable
18 21.7948 3.4000 1.74400 44.78
19 -29.6145 0.1500
20 16.7821 3.9000 1.57099 50.80
21 -16.7735 0.7000 1.80518 25.42
22 16.8017 Variable
23 * -100.0000 2.0000 1.53368 55.90
24 * -14.8007 2.2000
25 ∞ 1.0000 1.51633 64.14
26 ∞ 0.3000
27 ∞ 0.7000 1.51633 64.14
28 ∞ 0.5313
Image plane (imaging plane) ∞

Aspheric data 8th surface
K = 0.
A2 = 0.0000E + 00, A4 = -4.2787E-04, A6 = 7.8053E-06, A8 = 3.9279E-09, A10 = 0.0000E + 00

9th page
K = 0.
A2 = 0.0000E + 00, A4 = -6.1721E-04, A6 = 9.3376E-06, A8 = -3.7342E-08, A10 = 0.0000E + 00

14th page
K = 0.
A2 = 0.0000E + 00, A4 = -9.3961E-05, A6 = 1.0370E-07, A8 = 0.0000E + 00, A10 = 0.0000E + 00

15th page
K = 0.
A2 = 0.0000E + 00, A4 = 8.9752E-05, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

23rd page
K = 0.
A2 = 0.0000E + 00, A4 = -4.1583E-04, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

24th page
K = 0.
A2 = 0.0000E + 00, A4 = 1.2097E-04, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

Various data
Wide angle Medium telephoto
FL 4.02662 13.51272 45.43028
Fno 1.8491 2.2611 2.8153
ω 38.3 12.3 3.7
Image height 3.00 3.00 3.00
Total lens length 98.3054 98.3000 98.3136
BF 0.53127 0.53000 0.53939

d5 0.70000 19.78246 29.85000
d12 30.78700 11.75238 1.63700
d17 18.23547 12.37137 6.16873
d22 2.62653 8.43863 14.69327

Zoom lens group data
G Start surface Focal length
1 1 53.83635
2 6 -7.37469
3 13 28.78326
4 18 21.28816
5 23 32.28739

Numerical Example 4
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 57.4312 1.1000 1.84666 23.78
2 34.2144 8.9948 1.48749 70.23
3 642.8284 0.1500
4 33.1748 5.1517 1.72916 54.68
5 95.8748 Variable
6 400.0000 1.1000 1.72916 54.68
7 7.0807 4.2788
8 * 43.0000 1.1000 1.53368 55.90
9 * 17.1612 1.6669
10 -15.8946 0.8500 1.59282 68.63
11 265.2395 2.2000 1.94595 17.98
12 -29.1259 Variable
13 (Aperture) ∞ 0.7000
14 * 13.4810 3.2000 1.53368 55.90
15 * -18.6665 0.1500
16 181.9738 0.7000 1.84666 23.78
17 20.3665 Variable
18 20.6599 3.4000 1.72342 37.95
19 -33.9741 0.1500
20 16.2761 3.8000 1.58313 59.38
21 -16.2761 0.7000 1.80518 25.42
22 15.8190 Variable
23 * -100.0000 1.6000 1.53368 55.90
24 * -13.8070 2.7000
25 ∞ 1.0000 1.51633 64.14
26 ∞ 0.3000
27 ∞ 0.7000 1.51633 64.14
28 ∞ 0.5309
Image plane (imaging plane) ∞

Aspheric data 8th surface
K = 0.
A2 = 0.0000E + 00, A4 = -4.4787E-04, A6 = 7.3678E-06, A8 = -4.4682E-08, A10 = 0.0000E + 00

9th page
K = 0.
A2 = 0.0000E + 00, A4 = -7.1046E-04, A6 = 8.7428E-06, A8 = -1.1765E-07, A10 = 0.0000E + 00

14th page
K = 0.
A2 = 0.0000E + 00, A4 = -8.2921E-05, A6 = 6.5431E-08, A8 = 0.0000E + 00, A10 = 0.0000E + 00

15th page
K = 0.
A2 = 0.0000E + 00, A4 = 7.9777E-05, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

23rd page
K = 0.
A2 = 0.0000E + 00, A4 = -4.8081E-04, A6 = 8.0925E-06, A8 = 1.0950E-07, A10 = 0.0000E + 00

24th page
K = 0.
A2 = 0.0000E + 00, A4 = 2.9366E-05, A6 = 5.2804E-06, A8 = 1.9690E-07, A10 = 0.0000E + 00

Various data
Wide angle Medium telephoto
FL 3.99831 13.53193 45.87518
Fno 1.8421 2.2119 2.8553
ω 38.5 12.4 3.7
Image height 3.00 3.00 3.00
Total lens length 98.4411 98.4100 98.4452
BF 0.53091 0.53200 0.53496

d5 0.70000 20.57107 31.58374
d12 32.48400 12.62172 1.60026
d17 16.30236 10.74618 5.55462
d22 2.73164 8.24682 13.47938

Zoom lens group data
G Start surface Focal length
1 1 55.46328
2 6 -7.99405
3 13 29.92609
4 18 22.98715
5 23 29.82289

Numerical Example 5
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 57.8120 1.1000 1.84666 23.78
2 34.2860 9.0000 1.48749 70.23
3 672.7620 0.1500
4 33.4940 5.1500 1.72916 54.68
5 99.7360 Variable
6 401.8870 1.1000 1.72916 54.68
7 7.1280 4.2800
8 * 43.0000 1.1000 1.53368 55.90
9 * 17.6153 1.6700
10 -16.7900 0.8500 1.63854 55.45
11 104.6070 2.2000 1.94595 17.98
12 -30.7220 Variable
13 (Aperture) ∞ 0.7000
14 * 13.2039 3.2000 1.53368 55.90
15 * -19.6413 0.1500
16 99.9290 0.7000 1.84666 23.78
17 18.7490 Variable
18 20.5380 3.4000 1.72342 37.95
19 -34.2440 0.1500
20 16.1190 3.8000 1.58313 59.38
21 -16.1190 0.7000 1.80518 25.42
22 15.8610 Variable
23 * -100.0000 1.6000 1.53368 55.90
24 * -13.9435 2.7000
25 ∞ 1.0000 1.51633 64.14
26 ∞ 0.3000
27 ∞ 0.7000 1.51633 64.14
28 ∞ 0.5330
Image plane (imaging plane) ∞

Aspheric data 8th surface
K = 0.
A2 = 0.0000E + 00, A4 = -4.4787E-04, A6 = 7.3678E-06, A8 = -4.4682E-08, A10 = 0.0000E + 00

9th page
K = 0.
A2 = 0.0000E + 00, A4 = -7.0011E-04, A6 = 8.7587E-06, A8 = -1.1554E-07, A10 = 0.0000E + 00

14th page
K = 0.
A2 = 0.0000E + 00, A4 = -8.4732E-05, A6 = 4.6644E-08, A8 = 0.0000E + 00, A10 = 0.0000E + 00

15th page
K = 0.
A2 = 0.0000E + 00, A4 = 7.4993E-05, A6 = 0.0000E + 00, A8 = 0.0000E + 00, A10 = 0.0000E + 00

23rd page
K = 0.
A2 = 0.0000E + 00, A4 = -5.0232E-04, A6 = 8.8113E-06, A8 = 6.2288E-08, A10 = 0.0000E + 00

24th page
K = 0.
A2 = 0.0000E + 00, A4 = -1.0619E-05, A6 = 5.5555E-06, A8 = 1.6400E-07, A10 = 0.0000E + 00

Various data
Wide angle Medium telephoto
FL 4.00461 13.61600 46.25924
Fno 1.8421 2.2132 2.8656
ω 38.2 12.2 3.6
Image height 2.974 2.974 2.974
Total lens length 98.4600 98.4500 98.4636
BF 0.53296 0.53000 0.53657

d5 0.70000 20.61039 31.58400
d12 32.48400 12.60361 1.60000
d17 16.30720 10.74364 5.52358
d22 2.73580 8.26236 13.51942

Zoom lens group data
G Start surface Focal length
1 1 55.40660
2 6 -7.99089
3 13 30.01582
4 18 22.76022
5 23 30.16510

The corresponding values of the conditional expressions in each example are shown below.
Example 1 Example 2 Example 3 Example 4 Example 5
(1) log (β34T / β34W) 0.393 0.433 0.432 0.404 0.406
(2) | β2W | 0.211 0.195 0.192 0.202 0.202
(3) log (β2T / β2W) / logγ 0.627 0.590 0.591 0.619 0.617
(4) | β34W | 0.505 0.450 0.442 0.421 0.421
(5) f34W / f34T 1.381 1.379 1.375 1.288 1.291
(6) fW / f123T -0.0201 -0.0212 -0.0233 -0.0139 -0.0146
(7) f1 / fW 11.919 13.394 13.370 13.872 13.836
(8) f2 / f1 -0.145 -0.139 -0.137 -0.144 -0.144
(9) f4 / fW 5.478 5.491 5.281 5.744 5.679
(10) ff4 / f4 -1.194 -1.192 -1.162 -1.174 -1.173
(11) (R42F-R42R) / (R42F + R42R) 0.025 0.021 -0.001 0.014 0.008
(12) (R422F + R422R) / (R422F-R422R) 0.309 0.018 -0.001 0.014 0.008
(13) fb3 / f3 0.855 0.879 0.881 0.881 0.878
(14) (R32F-R32R) / (R32F + R32R) 0.473 0.935 0.974 0.799 0.684
(15) | β2T | 0.971 0.820 0.803 0.912 0.914
(16) | β34T | 1.249 1.220 1.196 1.067 1.073
(17) | βFW | 0.786 0.853 0.880 0.850 0.853

Moreover, the value of each parameter is shown below.
Example 1 Example 2 Example 3 Example 4 Example 5
β34T / β34W 2.473 2.711 2.706 2.538 2.549
β34W -0.505 -0.450 -0.442 -0.421 -0.421
β34T -1.249 -1.220 -1.196 -1.067 -1.073
β2W -0.211 -0.195 -0.192 -0.202 -0.202
β2T -0.971 -0.820 -0.803 -0.912 -0.914
β2T / β2W 4.602 4.205 4.182 4.525 4.525
f34W 20.020 19.280 19.178 18.538 18.554
f34T 14.497 13.980 13.946 14.39 14.369
γ = fT / fW 11.429 11.391 11.270 11.463 11.542
βFW 0.786 0.853 0.880 0.850 0.853

  The imaging (imaging) optical system according to the present invention as described above is an example of an imaging apparatus that captures an image of an object with an electronic imaging element such as a CCD or CMOS, particularly a digital camera, video camera, or information processing apparatus. It can be used for personal computers, telephones, mobile terminals, especially mobile phones that are convenient to carry. The embodiment is illustrated below.

  FIGS. 11 to 13 are conceptual diagrams of a configuration in which the imaging optical system according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 11 is a front perspective view showing the appearance of the digital camera 40, FIG. 12 is a rear perspective view thereof, and FIG. 3 is a cross-sectional view showing an optical configuration of the digital camera 40.

  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 45, a flash 46, a liquid crystal display monitor 47, and the like. Then, when the photographer presses the shutter 45 disposed on the upper part of the camera 40, photographing is performed through the photographing optical system 41, for example, the imaging optical system 48 of the first embodiment in conjunction therewith.

  The object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49. 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 image processing means 51. Further, the image processing means 51 is provided with a memory or the like, and can record a captured electronic image. This memory may be provided separately from the image processing means 51, or may be configured to perform recording and writing electronically using a flexible disk, memory card, MO, or the like.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a cover lens 54, a first prism 10, an aperture stop 2, a second prism 20, and a focusing lens 66. An object image is formed on the imaging surface 67 by the finder objective optical system 53. This object image is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind the Porro prism 55, an eyepiece optical system 59 for guiding the image formed into an erect image to the observer eyeball E is disposed.

According to the digital camera 40 configured as described above, an electronic imaging apparatus having a compact and thin imaging optical system in which the number of components of the photographing optical system 41 is reduced can be realized. The present invention is not limited to the above-described retractable digital camera, but can also be applied to a folding digital camera that employs a bending optical system.
Further, an autofocus mechanism 500 integrated with the photographing optical system 41 is provided. By mounting the autofocus mechanism 500, it is possible to focus at any subject distance.

In addition, it is desirable that the photographing optical system 41 and the electronic image sensor chip (electronic image sensor) are integrated.
By integrating the electronic image pickup element, an optical image obtained by the image pickup optical system can be converted into an electric signal. In addition, it is possible to provide a small and high-performance digital camera (imaging device) by selecting an electronic image sensor that can reduce a change in image brightness between the central portion and the peripheral portion of the image.

  Next, a personal computer which is an example of an information processing apparatus in which the imaging optical system of the present invention is incorporated as an objective optical system is shown in FIGS. 14 is a front perspective view of the personal computer 300 with the cover open, FIG. 15 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 16 is a side view of FIG. As shown in FIGS. 14 to 16, the personal computer 300 includes a keyboard 301, information processing means and recording means, a monitor 302, and a photographing optical system 303.

  Here, the keyboard 301 is for an operator to input information from the outside. The information processing means and recording means are not shown. The monitor 302 is for displaying information to the operator. The photographing optical system 303 is for photographing an image of the operator himself or a surrounding area. The monitor 302 may be a liquid crystal display element, a CRT display, or the like. Examples of the liquid crystal display element include a transmissive liquid crystal display element that illuminates from the back with a backlight (not shown), and a reflective liquid crystal display element that reflects and displays light from the front. Further, in the drawing, the photographing optical system 303 is built in the upper right of the monitor 302. However, the imaging optical system 303 is not limited to the place, and may be anywhere around the monitor 302 or the keyboard 301.

  The photographic optical system 303 includes, on the photographic optical path 304, the objective optical system 100 including, for example, the imaging optical system according to the first embodiment, and the electronic imaging element chip 162 that receives an image. These are built in the personal computer 300.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166. Finally, the object image is displayed on the monitor 302 as an electronic image. FIG. 14 shows an image 305 taken by the operator as an example. The image 305 can also be displayed on a communication partner's personal computer from a remote location via the processing means. The Internet and telephone are used for image transmission to remote places.
Further, an autofocus mechanism 500 integrated with the objective optical system 100 (imaging optical system) is provided. By mounting the autofocus mechanism 500, it is possible to focus at any subject distance.

It is desirable that the objective optical system 100 (imaging optical system) and the electronic imaging element chip 162 (electronic imaging element) are integrated.
By integrating the electronic image pickup element, an optical image obtained by the image pickup optical system can be converted into an electric signal. In addition, a small and high-performance personal computer (imaging device) can be provided by selecting an electronic imaging device that can reduce the change in image brightness between the central portion and the peripheral portion of the image.

  Next, a telephone which is an example of an information processing apparatus in which the imaging optical system of the present invention is built in as a photographing optical system, particularly a portable telephone which is convenient to carry is shown in FIG. 17A is a front view of the mobile phone 400, FIG. 17B is a side view, and FIG. 17C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 17A to 17C, the mobile phone 400 includes a microphone unit 401, a speaker unit 402, an input dial 403, a monitor 404, a photographing optical system 405, an antenna 406, and processing. Means.

  Here, the microphone unit 401 is for inputting an operator's voice as information. The speaker unit 402 is for outputting the voice of the other party. An input dial 403 is used by an operator to input information. The monitor 404 is for displaying information such as a photographed image of the operator himself or the other party, a telephone number, and the like. The antenna 406 is for transmitting and receiving communication radio waves. The processing means (not shown) is for processing image information, communication information, input signals, and the like.

  Here, the monitor 404 is a liquid crystal display element. Further, in the drawing, the arrangement positions of the respective components, in particular, are not limited thereto. The photographing optical system 405 includes the objective optical system 100 disposed on the photographing optical path 407 and an electronic image sensor chip 162 that receives an object image. As the objective optical system 100, for example, the imaging optical system of Example 1 is used. These are built in the mobile phone 400.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic imaging element chip 162 is input to an image processing unit (not shown) via the terminal 166. Finally, the object image is displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. The processing means includes a signal processing function. When transmitting an image to a communication partner, this function converts information on the object image received by the electronic image sensor chip 162 into a signal that can be transmitted.
Further, an autofocus mechanism 500 integrated with the objective optical system 100 (imaging optical system) is provided. By mounting the autofocus mechanism 500, it is possible to focus at any subject distance.

Further, it is desirable to integrate the objective optical system 100 (imaging optical system) and the electronic imaging element chip 162 (electronic imaging element).
By integrating the electronic image pickup device, an optical image by the image pickup optical system can be converted into an electric signal. In addition, it is possible to provide a small and high-performance mobile phone (imaging device) by selecting an electronic imaging device that can reduce a change in image brightness between the central portion and the peripheral portion of the image.

  The present invention can take various modifications without departing from the spirit of the present invention.

  As described above, the present invention is suitable for an imaging optical system in which various aberrations, particularly coma aberration, are corrected well, and an imaging apparatus using the imaging optical system.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens CG Cover glass I Imaging surface S Aperture stop 40 Digital camera 41 Imaging optical system 42 Imaging optical path 43 Viewfinder optical system 44 Viewfinder optical path 45 Shutter 46 Flash 47 LCD monitor 48 Lens 49 CCD
DESCRIPTION OF SYMBOLS 50 Image pick-up surface 51 Processing means 53 Finder objective optical system 55 Porro prism 57 Field frame 59 Eyepiece optical system 66 Focusing lens 67 Imaging surface 100 Objective optical system 102 Cover glass 162 Electronic image pick-up element chip | tip 166 Terminal 300 Personal computer 301 Keyboard 302 Monitor 303 Imaging Optical System 304 Imaging Optical Path 305 Image 400 Mobile Phone 401 Microphone Unit 402 Speaker Unit 403 Input Dial 404 Monitor 405 Imaging Optical System 406 Antenna 407 Imaging Optical Path 500 Autofocus Mechanism

Claims (17)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power And a final lens group having a positive refractive power,
At the time of zooming from the wide angle end to the telephoto end, the first lens group is fixed, the second lens group is moved to the image plane side, the third lens group is fixed, and the fourth lens group is Move and
The fourth lens group moves during focusing,
A zoom lens satisfying the following conditional expression (1):
0.20 <log (β34T / β34W) <0.9 · logγ (1)
However,
β34W is the magnification of the combined system of the third lens group and the fourth lens group at the wide-angle end,
β34T is the magnification of the combined system of the third lens group and the fourth lens group at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (2) is satisfied.
0.1 <| β2W | <0.30 (2)
However,
β2W is the magnification of the second lens group at the wide-angle end, and the magnification at the time of focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied.
0.3 <log (β2T / β2W) / logγ <0.8 (3)
However,
β2W is the magnification of the second lens group at the wide-angle end,
β2T is the magnification of the second lens group at the telephoto end,
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,
γ = fT / fW> 7,
In either case, the magnification or focal length when focusing on an object point at infinity,
It is. The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression (4) is satisfied.
0.30 <| β34W | <0.70 (4)
However,
β34W is a magnification of the combined system of the third lens group and the fourth lens group at the wide angle end, and is a magnification at the time of focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied.
1.10 <f34W / f34T <2.00 (5)
However,
f34W is the focal length of the combined system of the third lens group and the fourth lens group at the wide angle end,
f34T is the focal length of the combined system of the third lens group and the fourth lens group at the telephoto end,
Both are magnifications when focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (6) is satisfied.
-0.5 <fW / f123T <0.10 (6)
However,
fW is the focal length of the entire zoom lens system at the wide-angle end,
f123T is the focal length of the synthesis system from the first lens group to the third lens group at the telephoto end,
Both are focal lengths when focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (7) is satisfied.
9 <f1 / fW <18 (7)
However,
f1 is a focal length of the first lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (8) is satisfied.
-0.18 <f2 / f1 <-0.06 (8)
However,
f1 is a focal length of the first lens group,
f2 is the focal length of the second lens group,
It is. The zoom lens according to claim 1, wherein the following conditional expression (9) is satisfied.
4.0 <f4 / fW <10.0 (9)
However,
f4 is a focal length of the fourth lens group,
fW is the focal length of the entire zoom lens system at the wide-angle end, and the focal length when focusing on an object point at infinity,
It is. The zoom lens according to claim 1, wherein the following conditional expression (10) is satisfied.
-2.00 <ff4 / f4 <-1.00 (10)
However,
f4 is a focal length of the fourth lens group,
ff4 is the distance from the most object side surface top of the fourth lens group to the front focal position of the fourth lens group,
It is. 11. The zoom lens according to claim 1, wherein the fourth lens group includes a lens component having a positive refractive power and a lens component having a negative refractive power in order from the object side. .
However,
The lens component is a single lens or a cemented lens, and has two optical surfaces in contact with air.
It is. The zoom lens according to claim 11, wherein the following conditional expression (11) is satisfied.
-0.3 <(R42F-R42R) / (R42F + R42R) <0.6 (11)
However,
R42F is the paraxial radius of curvature of the object side surface of the lens component having the negative refractive power of the fourth lens group,
R42R is the paraxial radius of curvature of the image side surface of the lens component having the negative refractive power of the fourth lens group,
It is. The lens component of the negative refractive power of the fourth lens group is a cemented lens,
The cemented lens is composed of a single lens with positive refractive power and a single lens with negative refractive power in order from the object side
The zoom lens according to claim 11, wherein the following conditional expression (12) is satisfied.
-0.5 <(R422F + R422R) / (R422F-R422R) <1.2 (12)
However,
R422F is a paraxial radius of curvature of the object side surface of the negative lens single lens of the fourth lens group,
R422R is the paraxial radius of curvature of the image side surface of the single lens having the negative refractive power of the fourth lens group,
It is. The zoom lens according to claim 1, wherein the following conditional expression (13) is satisfied.
0.50 <fb3 / f3 <1.5 (13)
However,
f3 is the focal length of the third lens group,
fb3 is a distance from the most image side surface top of the third lens group to the rear focal position of the third lens group;
It is. The third lens group includes, in order from the object side, two lens components, a lens component having a positive refractive power and a lens component having a negative refractive power,
The zoom lens according to claim 1, wherein the following conditional expression (14) is satisfied.
0.1 <(R32F-R32R) / (R32F + R32R) <5.0 (14)
However,
R32F is the paraxial radius of curvature of the object side surface of the lens component having the negative refractive power of the third lens group,
R32R is the paraxial radius of curvature of the image side surface of the lens component having the negative refractive power of the third lens group,
The lens component is a single lens or a cemented lens, and has two optical surfaces in contact with air.
It is. The zoom lens according to claim 1, wherein the final lens group includes a lens component having a positive refractive power.
However,
The lens component is a single lens or a cemented lens, and has two optical surfaces in contact with air.
It is. The zoom lens according to any one of claims 1 to 16, and
An imaging device comprising: an imaging device disposed on an image plane of the zoom lens.

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