JP4883266B2 - Zoom lens and imaging apparatus - Google Patents

Description

  The present invention relates to a zoom lens and an imaging apparatus equipped with the zoom lens.

  In recent years, in image pickup apparatuses such as small digital still cameras and video cameras equipped with small image pickup units equipped with solid-state image pickup devices such as CCD (Charge Coupled Devices) type image sensors or CMOS (Complementary Metal-Oxide Semiconductor) type image sensors. As the number of pixels of a solid-state image sensor increases, there is an increasing demand for a zoom lens having higher imaging performance. Further, further miniaturization is demanded for the zoom lens of the small imaging device.

As a small zoom lens for a small image pickup device, 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 refractive power. Some zoom lenses are made thin in the thickness direction by arranging a prism that bends the optical path in the first lens group and includes a fourth lens group (see, for example, Patent Document 1).
JP 2000-131610 A

  However, the conventional zoom lens as disclosed in Patent Document 1 has a long overall length compared to its focal length, and is unsuitable for use in a small imaging device.

  The present invention has been made in view of the above problems, and has a high imaging performance suitable for use in devices such as a digital still camera and a video camera using a high-pixel solid-state imaging device, and has a zoom ratio of 3 An object of the present invention is to provide a zoom lens that is about twice as small and an image pickup apparatus equipped with this zoom lens.

In order to solve the above problem, the zoom lens according to claim 1 is provided by:
In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The first lens group includes a reflective optical element for bending the optical path,
The second lens group includes a negative lens and a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
The fourth lens group includes at least two positive lenses, and is arranged in order from the object side along the optical axis, a cemented lens of a positive lens and a negative lens, and a concave surface on the image side on the optical axis. And a meniscus lens facing the head .

The zoom lens of the invention according to claim 2
In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The second lens group includes a negative lens and a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
The fourth lens group includes at least two positive lenses,
The first lens group includes a first lens having negative refractive power in order from the object side along the optical axis, a reflective optical element for bending the optical path, and a second lens having positive refractive power. And
2.0 <f1 / fw <4.5 (1)
1.0 <| f11 | / fw <5.0 (2)
1.0 <f12 / fw <4.0 (3)
(Where f1: focal length of the first lens group, f11: focal length of the first lens, f12: focal length of the second lens, fw: focal length at the wide angle end of the zoom lens)
It is characterized by satisfying .

The invention according to claim 3 is the zoom lens according to claim 1 or 2 ,
The fifth lens group comprises only one positive lens having at least one aspherical shape.

The zoom lens of the invention according to claim 4
In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The second lens group includes a cemented lens of a negative lens and a positive lens,
The fourth lens group includes at least two positive lenses,
The fifth lens group, Ri Do because only one positive lens having an aspherical shape of at least one surface,
The first lens group includes a first lens having negative refractive power in order from the object side along the optical axis, a reflective optical element for bending the optical path, and a second lens having positive refractive power. And
2.0 <f1 / fw <4.5 (1)
1.0 <| f11 | / fw <5.0 (2)
1.0 <f12 / fw <4.0 (3)
(Where f1: focal length of the first lens group, f11: focal length of the first lens, f12: focal length of the second lens, fw: focal length at the wide angle end of the zoom lens)
It is characterized by satisfying .

The invention according to claim 5 is the zoom lens according to any one of claims 1 to 4 ,
The third lens group is characterized in that its position on the optical axis is always fixed during zooming and focusing.

A sixth aspect of the present invention is the zoom lens according to any one of the first to fifth aspects,
An aperture stop on the object side on the optical axis of the third lens group;
The third lens group is composed of only one positive lens having at least one aspherical shape.

The invention according to claim 7 is the zoom lens according to claim 2 or 4 ,
The first lens group includes:
2.7 <f1 / fw <4.0 (1 ')
1.9 <| f11 | / fw <3.1 (2 ')
1.9 <f12 / fw <2.3 (3 ')
It is characterized by satisfying.

The invention according to claim 8 is the zoom lens according to any one of claims 1 to 7 ,
The reflective optical element comprises a prism that bends the optical path,
ndp> 1.6 (4)
(Where ndp is the refractive index of the prism at the d-line)
It is characterized by satisfying.

The invention according to claim 9 is the zoom lens according to claim 8 ,
The reflective optical element is
ndp> 1.84 (4 ')
It is characterized by satisfying.

The imaging device of the invention according to claim 10 is,
The zoom lens according to any one of claims 1 to 9 ,
And an image pickup device for picking up an image of light incident through the zoom lens.

According to the first aspect of the invention, the configuration of the second lens group can effectively correct off-axis chromatic aberration in the entire zooming range. In addition, the configuration of the fourth lens group including at least two positive lenses and having a relatively large refractive power in the lens group can suppress the occurrence of spherical aberration, coma aberration, and field curvature. Furthermore, the configuration of the fourth lens group can suppress the occurrence of spherical aberration, coma aberration, astigmatism, field curvature, and chromatic aberration, and can correct distortion.

According to the second aspect of the present invention, the configuration of the second lens group can effectively correct off-axis chromatic aberration in the entire zooming range. In addition, the configuration of the fourth lens group having a relatively large refractive power in the lens group can suppress the occurrence of spherical aberration, coma aberration, and field curvature.

According to the third aspect of the present invention, it is possible to effectively correct curvature of field and distortion, and to obtain good image side telecentric characteristics. Here, it is desirable that one positive lens constituting the fifth lens group is a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

According to the fourth aspect of the present invention, the configuration of the second lens group makes it possible to efficiently secure the amount of movement of the second lens group while suppressing the occurrence of chromatic aberration, and the zoom ratio of the zoom lens. Easy to secure. In addition, the configuration of the fourth lens group having a relatively strong refractive power in the lens group can suppress the occurrence of spherical aberration, coma aberration, and field curvature.

  In addition, the configuration of the fifth lens group can effectively correct curvature of field and distortion, and can provide good image-side telecentric characteristics. Here, it is desirable that one positive lens constituting the fifth lens group is a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

According to the fifth aspect of the present invention, it is possible to simplify the lens driving mechanism of the imaging apparatus equipped with the zoom lens, and to reduce the thickness of the imaging apparatus in the thickness direction.

According to the sixth aspect of the present invention, the entrance pupil position can be brought closer to the object side on the optical axis by the arrangement of the aperture stop, and the diameter of the lens closest to the object side on the optical axis of the first lens group The reflective optical element can be made smaller, and therefore the thickness of the imaging device in the thickness direction can be reduced. In addition, with the configuration of the third lens group and the aperture stop, it is possible to effectively correct spherical aberration, coma aberration, and field curvature while securing a moving space for the second lens group and the fourth lens group.

According to the second and fourth aspects of the present invention, the diameter of the light beam incident on the reflecting optical element is reduced, so that the reflecting optical element can be reduced in size, and the thickness in the thickness direction of the imaging apparatus equipped with such a zoom lens can be reduced. Can be thinned.

  In Formula (1), when f1 / fw exceeds the lower limit, the refractive power of the first lens group does not become too strong, and the occurrence of aberrations occurring in the first lens group can be suppressed. Further, when f1 / fw is less than the upper limit, the refractive power of the first lens group becomes strong, and thereby the amount of movement of the second lens group, which is a variable power group, can be reduced, and therefore the overall length of the zoom lens can be shortened. Can do.

  In Expression (2), when | f11 | / fw exceeds the lower limit, it is possible to suppress the occurrence of distortion aberration that occurs in the first lens. Also, if | f11 | / fw is below the upper limit, the diameter of the light beam incident on the reflective optical element can be reduced, thereby reducing the size of the reflective optical element for bending the optical path. The thickness in the thickness direction of the imaging device can be reduced.

  Further, in Formula (3), when f12 / fw exceeds the lower limit, the refractive power of the second lens does not become too strong, and generation of spherical aberration or the like that occurs in the second lens can be suppressed. Further, when f12 / fw is lower than the upper limit, the refractive power of the second lens is increased, and thereby the amount of movement of the second lens group which is a variable power group can be reduced, and thus the overall length of the zoom lens can be shortened. it can. In addition, it is possible to correct distortion occurring in the first lens.

According to invention of Claim 7 , the effect of the invention of Claim 2 can be heightened by satisfy | filling Formula (1 '), (2'), (3 ').

According to the eighth aspect of the present invention, the diameter of the light beam passing through the prism is reduced by refraction at the incident surface of the prism, so that the prism can be reduced in size, and the thickness direction of the imaging device equipped with such a zoom lens can be reduced. The thickness can be reduced.

  In Expression (4), when the lower limit is exceeded, the diameter of the light beam passing through the prism is reduced, so that the prism can be reduced in size and the thickness in the thickness direction of the imaging device can be reduced.

According to invention of Claim 9 , the effect of the invention of Claim 8 can be heightened by satisfy | filling Formula (4 ').

According to the tenth aspect of the present invention, a small imaging device can be obtained.

  Hereinafter, a first embodiment and a second embodiment according to the present invention will be described in detail in order with reference to the accompanying drawings. However, the scope of the invention is not limited to the examples described.

  In the present specification, the “thickness direction” refers to the same direction as the optical axis direction of the incident surface in the reflective optical element of the first lens group.

  Further, “image side telecentric characteristics” in this specification will be described. A zoom lens used in an image pickup apparatus including a solid-state image pickup device is required to be image side telecentric in order to obtain good light receiving sensitivity over the entire screen. The image side telecentric means that the principal ray is incident on the imaging surface of the solid-state imaging device at an angle parallel to the optical axis at each image height. In recent years, it is possible to correct the image-side telecentric dissatisfaction amount by appropriately arranging the microlens array on the imaging surface of the solid-state imaging device. It is common to use a substantially image side telecentric imaging lens that is incident at an angle of about 5 ° to 30 °. At this time, in order to obtain good light receiving sensitivity and image quality over the entire screen, it has a substantially image side telecentric characteristic that the chief ray incident angle on the imaging surface uniformly increases with respect to the image height. desirable. Therefore, in this specification, “good image side telecentric characteristics” means that the incident angle of the principal ray at the outermost periphery of the imaging surface is about 20 ° or less.

  In addition, the term “plastic lens” in the present specification includes a lens made of a plastic material as a base material, in which small particles are dispersed in the plastic material, and having a plastic volume ratio of more than half. In addition, the case where the surface is subjected to coating treatment for the purpose of preventing reflection and improving surface hardness is also included.

(First embodiment)
A first embodiment according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows an internal configuration of the digital still camera 100 of the present embodiment.

  As shown in FIG. 1, a digital still camera 100 as an imaging apparatus includes an optical system 101, a solid-state imaging device 102, an A / D conversion unit 103, a control unit 104, an optical system driving unit 105, and timing generation. A unit 106, an image sensor driving unit 107, an image memory 108, an image processing unit 109, an image compression unit 110, an image recording unit 111, a display unit 112, and an operation unit 113 are configured.

  The optical system 101 is an optical system including a zoom lens 1 described later, and receives light from a subject. The solid-state imaging device 102 is an imaging device such as a CCD or CMOS, and photoelectrically converts incident light for each of R, G, and B and outputs an analog signal thereof. The A / D conversion unit 103 converts an analog signal into digital image data.

  The control unit 104 controls each unit of the digital still camera 100. The control unit 104 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), and various programs read from the ROM and expanded in the RAM, and various types of programs in cooperation with the CPU. Execute the process.

  The optical system drive unit 105 controls the drive of the optical system 101 in zooming, focusing (movement of a second lens group 20 and a fourth lens group 40 described later), exposure, and the like under the control of the control unit 104. The timing generator 106 outputs a timing signal for analog signal output. The image sensor drive unit 107 performs scanning drive control of the solid-state image sensor 102.

  The image memory 108 stores image data so as to be readable and writable. The image processing unit 109 performs various image processes on the image data. The image compression unit 110 compresses captured image data by a compression method such as JPEG (Joint Photographic Experts Group). The image recording unit 111 records image data on a recording medium such as an SD (Secure Digital) memory card, a memory stick, or an xD picture card set in a slot (not shown).

  The display unit 112 is a color liquid crystal panel or the like, and displays image data after shooting, a through image before shooting, various operation screens, and the like. The operation unit 113 includes a release button, various modes, and various operation keys for setting values, and outputs information input by the user to the control unit 104.

  Here, the operation of the digital still camera 100 will be described. In subject photographing, subject monitoring (through image display) and image photographing execution are performed. In the monitoring, an image of the subject obtained through the optical system 101 is formed on the light receiving surface of the solid-state image sensor 102. A solid-state imaging device 102 disposed behind the imaging optical axis of the optical system 101 is scanned and driven by a timing generation unit 106 and an imaging device driving unit 107, and serves as a photoelectric conversion output corresponding to an optical image formed at regular intervals. Output analog signal for one screen.

  The analog signal is appropriately gain-adjusted for each primary color component of RGB, and then converted into digital data by the A / D conversion unit 103. The digital data is subjected to color process processing including pixel interpolation processing and γ correction processing by the image processing unit 109 to generate a luminance signal Y and color difference signals Cb, Cr (image data) as digital values, and the image memory. 108, the signal is periodically read out and the video signal is generated and output to the display unit 112.

  The display unit 112 functions as an electronic viewfinder in monitoring, and displays captured images in real time. In this state, scaling, focusing, exposure, and the like of the optical system 101 are set as needed based on an operation input via the user operation unit 113.

  In such a monitoring state, when the user depresses the release button of the operation unit 113 at a timing at which still image shooting is desired, still image data is shot. At the timing when the release button is pressed, one frame of image data stored in the image memory 108 is read out and compressed by the image compression unit 110. The compressed image data is recorded on a recording medium by the image recording unit 111.

  FIG. 2 shows a configuration of the zoom lens 1 included in the optical system 101. The zoom lens 1 includes, in order from the object side (subject side) to the image plane IMG side along the optical axis O1, a first lens group 10 having a positive refractive power, a second lens group 20 having a negative refractive power, and an aperture. A stop D1, a third lens group 30 having a positive refractive power, a fourth lens group 40 having a positive refractive power, a fifth lens group 50 having a positive refractive power, a low-pass filter 61, a cover glass 62, It is configured with. The image plane IMG is a light receiving surface of the solid-state image sensor 102. Instead of the low pass filter 61, an infrared cut filter may be provided.

  When the zoom lens 1 is zoomed and focused from the wide-angle end to the telephoto end, the positions of the first lens group 10, the third lens group 30, the fifth lens group 50, and the aperture stop D1 are unchanged on the optical axis O1. Yes, the second lens group 20 and the fourth lens group 40 move on the optical axis O1. Specifically, in zooming from the wide-angle end to the telephoto end, the second lens group 20 moves so that the distance between the first lens group 10 and the second lens group 20 increases, and the third lens group 30 and the third lens group 30 The fourth lens group 40 moves so that the distance from the fourth lens group 40 is narrowed. At the time of focusing, at least the fourth lens group 40 moves along the optical axis O1.

  The first lens group 10 includes, in order from the object side to the image plane IMG side, along the optical axis O1, a negative lens 11 having a negative refractive power, and reflective optics having a function of bending the optical path by reflecting light rays by 90 °. A prism 13 as an element and a positive lens 12 having a positive refractive power are provided. In order from the object side to the image plane IMG side along the optical axis O1, the negative lens 11 has surfaces S1 and S2, the prism 13 has surfaces S3, (reflection) surfaces S4 and S5, and the positive lens 12 has It has surfaces S6 and S7.

  The second lens group 20 includes a negative lens 21 and a cemented lens of the negative lens 22 and the positive lens 23 in order along the optical axis O1 from the object side to the image plane IMG side. In order from the object side to the image plane IMG side along the optical axis O1, the negative lens 21 has surfaces S8 and S9, and the negative lens 22 and the positive lens 23 have surfaces S10 to S12.

  The third lens group 30 is configured to include only an aspheric positive lens 31 that is positioned in the vicinity of the image side on the optical axis O1 of the aperture stop D1. In order from the object side to the image plane IMG side along the optical axis O1, the aperture stop D1 has a surface S13, and the positive lens 31 has surfaces S14 and S15.

  The fourth lens group 40 includes, in order from the object side to the image plane IMG side along the optical axis O1, a positive lens 41, a cemented lens in which the positive lens 42 and the negative lens 43 are cemented, and the image side in the optical axis O1 direction. And a plastic meniscus lens 44 having a concave surface (surface S22). In order from the object side to the image plane IMG side along the optical axis O1, the positive lens 41 has surfaces S16 and S17, the positive lens 42 and the negative lens 43 have surfaces S18 to S20, and the meniscus lens 44 has a surface S21. , S22.

  The fifth lens group 50 includes only at least one aspherical positive lens 51. The positive lens 51 has surfaces S23 and S24 in order along the optical axis O1 from the object side to the image plane IMG side. The low-pass filter 61 has surfaces S25 and S26 in order along the optical axis O1 from the object side to the image plane IMG side. The cover glass 62 has surfaces S27 and S28 in order along the optical axis O1 from the object side to the image plane IMG side.

The shape of each aspheric surface of the lens is as follows. In an orthogonal coordinate system with the vertex of the surface as the origin and the optical axis direction as the X axis, the vertex curvature is C, the conic constant is K, and the aspheric coefficients are A4, A6, A8, A10 , A12 are expressed by the following equation (5).

The first lens group 10 satisfies the following expressions (1), (2), and (3).
2.0 <f1 / fw <4.5 (1)
1.0 <| f11 | / fw <5.0 (2)
1.0 <f12 / fw <4.0 (3)
Where f1 is the focal length of the first lens group 10, f11 is the focal length of the negative lens 11, f12 is the focal length of the positive lens 12, and fw is the focal length of the zoom lens 1 at the wide angle end.

  Expression (1) is an expression that defines the range of the ratio between the focal length of the first lens group 10 and the focal length at the wide-angle end of the zoom lens 1. Expression (2) is an expression that defines the range of the ratio between the focal length of the negative lens 11 and the focal length at the wide-angle end of the zoom lens. Expression (3) is an expression that defines the range of the ratio between the focal length of the positive lens 12 and the focal length at the wide-angle end of the zoom lens.

The prism 13 satisfies the following expression (4).
ndp> 1.6 (4)
Where ndp is the refractive index of the prism 13 at the d-line. Formula (4) is a formula which prescribes | regulates the range of the refractive index of prism 13 material.

  According to the present embodiment, the second lens group 20 includes the negative lens 21 and the cemented lens of the negative lens 22 and the positive lens 23, thereby effectively correcting off-axis chromatic aberration in the entire zooming range. it can. In addition, the fourth lens group 40 having a relatively large refractive power in the lens group includes the two positive lenses 41 and 42, thereby suppressing the occurrence of spherical aberration, coma aberration, and field curvature. Can do.

  Further, the fourth lens group 40 is arranged in order from the object side along the optical axis O1, a cemented lens of the positive lens 42 and the negative lens 43 in order from the object side, and a meniscus lens 44 having a concave surface facing the image side on the optical axis O1. Thus, the occurrence of spherical aberration, coma aberration, astigmatism, field curvature and chromatic aberration can be suppressed, and distortion can be corrected.

  In addition, by always fixing the position of the third lens group 30 in the optical axis O1 direction during zooming and focusing, the optical system driving unit 105 of the digital still camera 100 can be simplified, and the digital still camera 100 can be simplified. The thickness in the thickness direction can be reduced.

  Further, by arranging the aperture stop D1 on the object side of the third lens group 30, the entrance pupil position can be brought closer to the object side on the optical axis O1, and the most object on the optical axis O1 of the first lens group 10 can be obtained. The diameter of the positive lens 12 on the side and the prism 13 can be reduced, and therefore the thickness of the digital still camera 100 in the thickness direction can be reduced. Further, the third lens group 30 is made close to the aperture stop D1 and is constituted by a positive lens 31 as a single lens having at least one aspherical shape, so that the second lens group 20 and the fourth lens group 40 Spherical aberration, coma aberration, and field curvature can be effectively corrected while securing a moving space.

  In addition, since the first lens group 10 includes the negative lens 11, the prism 13, and the positive lens 12 in order from the object side along the optical axis O1, the diameter of the light beam incident on the prism 13 is reduced. The prism 13 can be reduced in size, and the thickness in the thickness direction of the digital still camera 100 on which the zoom lens 1 is mounted can be reduced.

Further, in the above formula (1), when f1 / fw exceeds the lower limit (2.0), the refractive power of the first lens group 10 does not become too strong, and the occurrence of aberrations occurring in the first lens group 10 is suppressed. Can do. In addition, when f1 / fw is less than the upper limit (4.5), the refractive power of the first lens group 10 becomes strong, thereby reducing the amount of movement of the second lens group 20 which is a variable power group, and therefore the zoom lens is The overall length can be shortened. Moreover, when the range of following Formula (1 ') is satisfy | filled, since the said effect increases, it is desirable.
2.7 <f1 / fw <4.0 (1 ')

Further, in the above formula (2), when | f11 | / fw exceeds the lower limit (1.0), it is possible to suppress the occurrence of distortion occurring in the negative lens 11. Further, when | f11 | / fw is less than the upper limit (5.0), the diameter of the light beam incident on the prism 13 can be reduced, and thereby the size of the prism 13 for bending the optical path can be reduced. The thickness in the thickness direction of the mounted digital still camera 100 can be reduced. Moreover, when the range of following Formula (2 ') is satisfy | filled, since the said effect increases, it is desirable.
1.9 <| f11 | / fw <3.1 (2 ')

Further, in the above formula (3), when f12 / fw exceeds the lower limit (1.0), the refractive power of the positive lens 12 does not become too strong, and the occurrence of spherical aberration or the like that occurs in the positive lens 12 can be suppressed. . Further, when f12 / fw is less than the upper limit (4.0), the refractive power of the positive lens 12 becomes strong, and thereby the amount of movement of the second lens group 20 which is a variable power group can be reduced. Can be shortened. In addition, it is possible to correct distortion occurring in the negative lens 11. Moreover, when the range of following Formula (3 ') is satisfy | filled, since the said effect increases, it is desirable.
1.9 <f12 / fw <2.3 (3 ')

  Further, by forming the fifth lens group 50 by one positive lens 51 having at least one aspherical shape, it is possible to effectively correct curvature of field and distortion, and a good image. Side telecentric characteristics can be obtained. Here, the single positive lens 51 constituting the fifth lens group 50 is desirably a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

  In addition, since the reflecting optical element is constituted by the prism 13, the diameter of the light beam passing through the prism 13 is reduced by refraction at the incident surface of the prism 13, so that the prism 13 can be miniaturized and the zoom lens 1 is mounted. The thickness of the digital still camera 100 in the thickness direction can be reduced.

In the above formula (4), when ndp exceeds the lower limit (1.6), the diameter of the light beam passing through the prism 13 is reduced, so that the prism 13 can be reduced in size and the thickness in the thickness direction of the digital still camera 100 is reduced. be able to. Moreover, when the range of following Formula (4 ') is satisfy | filled, since the said effect increases, it is desirable.
ndp> 1.84 (4 ')

  In addition, a small digital still camera 100 equipped with the zoom lens 1 can be obtained.

(Second Embodiment)
A second embodiment according to the present invention will be described with reference to FIG. The apparatus configuration of this embodiment is obtained by replacing the optical system 101 of the digital still camera 100 with an optical system including a zoom lens 2 described later, and the zoom lens 2 will be mainly described.

  FIG. 3 shows the configuration of the zoom lens 2. The zoom lens 2 includes, in order from the object side to the image plane IMG side, along the optical axis O2, a first lens group 210 having a positive refractive power, a second lens group 220 having a negative refractive power, an aperture stop D2, A third lens group 230 having a positive refractive power, a fourth lens group 240 having a positive refractive power, a fifth lens group 250 having a positive refractive power, a low-pass filter 261, and a cover glass 262. Is done. In place of the low-pass filter 261, an infrared cut filter may be provided.

  When the zoom lens 2 is zoomed and focused from the wide-angle end to the telephoto end, the positions of the first lens group 210, the third lens group 230, the fifth lens group 250, and the aperture stop D2 are unchanged on the optical axis O2. Yes, the second lens group 220 and the fourth lens group 240 move on the optical axis O2. Specifically, in zooming from the wide-angle end to the telephoto end, the second lens group 220 moves so that the distance between the first lens group 210 and the second lens group 220 increases, and the third lens group 230 and the second lens group 220 The fourth lens group 240 moves so that the distance from the fourth lens group 240 is narrowed. At the time of focusing, at least the fourth lens group 240 moves along the optical axis O2.

  The first lens group 210 includes, in order from the object side to the image plane IMG side along the optical axis O2, a negative lens 211, a prism 213 that has a function of bending the optical path by reflecting light rays, and a positive lens 212. It is configured with. In order from the object side to the image plane IMG side along the optical axis O2, the negative lens 211 has surfaces T1 and T2, the prism 213 has surfaces T3, (reflection) surfaces T4 and T5, and the positive lens 212 has It has surfaces T6 and T7.

  The second lens group 220 includes only a cemented lens of the negative lens 221 and the positive lens 222 in order along the optical axis O2 from the object side to the image plane IMG side. In order from the object side to the image plane IMG side along the optical axis O2, the negative lens 221 and the positive lens 222 have surfaces T8 to T10.

  The third lens group 230 is located in the vicinity of the image side on the optical axis O2 of the aperture stop D2, and includes only an aspherical positive lens 231. In order from the object side to the image plane IMG side along the optical axis O2, the aperture stop D2 has a surface T11, and the positive lens 231 has surfaces T12 and T13.

  The fourth lens group 240 includes, in order from the object side to the image plane IMG side along the optical axis O2, a positive lens 241, a negative lens 243 having a concave surface (surface T18) facing the positive lens 242, and the image side on the optical axis O2. And a cemented lens. In order from the object side to the image plane IMG side along the optical axis O2, the positive lens 241 has surfaces T14 and T15, and the positive lens 242 and the negative lens 243 have surfaces T16 to T18.

  The fifth lens group 250 includes at least one aspherical plastic positive lens 251 alone. The positive lens 251 has surfaces T19 and T20 in order along the optical axis O2 from the object side to the image plane IMG side. The low-pass filter 261 has surfaces T21 and T22 in order along the optical axis O2 from the object side to the image plane IMG side. The cover glass 262 has surfaces T23 and T24 in order along the optical axis O2 from the object side to the image plane IMG side.

  The shape of each aspheric surface of the lens satisfies the above formula (5). Further, when f1 is the focal length of the first lens group 210, f11 is the focal length of the negative lens 211, f12 is the focal length of the positive lens 212, and fw is the focal length at the wide angle end of the zoom lens 1, The one lens group 210 satisfies the above formulas (1), (2), and (3). Further, when ndp is the refractive index at the d-line of the prism 213, the prism 213 satisfies the above formula (4).

  According to the present embodiment, the second lens group 220 is configured only by the cemented lens of the negative lens 221 and the positive lens 222, so that the amount of movement of the second lens group 220 can be efficiently suppressed while suppressing the occurrence of chromatic aberration. It is easy to ensure the zoom ratio of the zoom lens 2. The fourth lens group 240 having a relatively strong refractive power in the lens group includes a positive lens 241 and a cemented lens of the positive lens 242 and the negative lens 243 in order from the object side on the optical axis O2. Thus, the occurrence of spherical aberration, coma aberration, and chromatic aberration can be suppressed.

  In addition, by constantly fixing the position of the third lens group 230 in the optical axis O2 direction during zooming and focusing, the optical system driving unit 105 of the digital still camera 100 can be simplified, and the digital still camera 100 can be simplified. The thickness in the thickness direction can be reduced.

  Also, by arranging the aperture stop D2 on the object side of the third lens group 230, the entrance pupil position can be brought closer to the object side on the optical axis O2, and the most object on the optical axis O2 of the first lens group 210. The diameter of the positive lens 212 on the side and the prism 213 can be reduced, so that the thickness of the digital still camera 100 in the thickness direction can be reduced. Further, the third lens group 230 is constituted by the positive lens 231 as a single lens having at least one aspherical shape in the vicinity of the aperture stop D2, so that the second lens group 220 and the fourth lens group 240 are formed. Spherical aberration, coma aberration, and field curvature can be effectively corrected while securing a moving space.

  Further, by configuring the first lens group 210 by the negative lens 211, the prism 213, and the positive lens 212 in order from the object side along the optical axis O2, the diameter of the light beam incident on the prism 213 is reduced, and accordingly The prism 213 can be reduced in size, and the thickness in the thickness direction of the digital still camera 100 on which the zoom lens 2 is mounted can be reduced.

  Further, in the above formula (1), when f1 / fw exceeds the lower limit (2.0), the refractive power of the first lens group 210 does not become too strong, and the occurrence of aberrations occurring in the first lens group 210 is suppressed. Can do. In addition, when f1 / fw is less than the upper limit (4.5), the refractive power of the first lens group 210 becomes strong, and thereby the amount of movement of the second lens group 220 which is a variable power group can be reduced. Can be shortened. Moreover, it is desirable to satisfy the range of the above formula (1 ') because the above effect is further enhanced.

  In the above formula (2), when | f11 | / fw exceeds the lower limit (1.0), it is possible to suppress the occurrence of distortion occurring in the negative lens 211. Further, when | f11 | / fw is less than the upper limit (5.0), the diameter of the light beam incident on the prism 213 can be reduced, thereby reducing the size of the prism 213 for bending the optical path. The thickness in the thickness direction of the mounted digital still camera 100 can be reduced. Moreover, it is desirable to satisfy the range of the above formula (2 ′) because the above effect is further enhanced.

  In the above formula (3), when f12 / fw exceeds the lower limit (1.0), the refractive power of the positive lens 212 does not become too strong, and the occurrence of spherical aberration and the like that occurs in the positive lens 212 can be suppressed. . Further, when f12 / fw is less than the upper limit (4.0), the refractive power of the positive lens 212 is increased, and thereby the amount of movement of the second lens group 220 which is a variable power group can be reduced. Can be shortened. Further, it is possible to correct distortion aberration generated in the negative lens 211. Moreover, it is desirable to satisfy the range of the above formula (3 ′) because the above effect is further enhanced.

  In addition, by forming the fifth lens group 250 with one positive lens 251 having at least one aspherical shape, it is possible to effectively correct curvature of field and distortion, and a good image. Side telecentric characteristics can be obtained. Here, it is desirable that the single positive lens 251 constituting the fifth lens group 250 is a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

  In addition, since the reflecting optical element is constituted by the prism 213, the diameter of the light beam passing through the prism 213 is reduced by refraction at the incident surface of the prism 213, so that the prism 213 can be reduced in size and the zoom lens 2 is mounted. The thickness of the digital still camera 100 in the thickness direction can be reduced.

  In the above formula (4), when ndp exceeds the lower limit (1.6), the diameter of the light beam passing through the prism 213 is reduced, so that the prism 213 can be miniaturized and the thickness of the digital still camera 100 in the thickness direction is reduced. be able to. Further, it is desirable to satisfy the range of the above formula (4 ′) because the above effect is further enhanced.

  In addition, a small digital still camera 100 equipped with the zoom lens 2 can be obtained.

(Third embodiment)
A third embodiment according to the present invention will be described with reference to FIG. The apparatus configuration of the present embodiment is obtained by replacing the configuration of the fourth lens group with a later-described fourth lens group 340 in the zoom lens 1 described in the first embodiment. A configuration different from the embodiment will be mainly described.

  FIG. 4 shows a configuration of the zoom lens 3 included in the optical system 101. The zoom lens 3 includes, in order from the object side to the image plane IMG side along the optical axis O3, a first lens group 310 having a positive refractive power, a second lens group 320 having a negative refractive power, an aperture stop D3, A third lens group 330 having a positive refractive power, a fourth lens group 340 having a positive refractive power, a fifth lens group 350 having a positive refractive power, a low-pass filter 361, and a cover glass 362. Is done. Instead of the low-pass filter 361, an infrared cut filter may be provided.

  The zoom lens 3 does not change the positions of the first lens group 310, the third lens group 330, the fifth lens group 350, and the aperture stop D3 on the optical axis O3 during zooming and focusing from the wide-angle end to the telephoto end. Yes, the second lens group 320 and the fourth lens group 340 move on the optical axis O3. Similarly to the first lens group 10 of the zoom lens 1, the first lens group 310 includes a negative lens 211, a prism 313, and a positive lens 312 in order along the optical axis O 3 from the object side to the image plane IMG side. And has surfaces U1-U7. Similar to the second lens group 20, the second lens group 320 includes, in order from the object side to the image plane IMG side along the optical axis O3, a negative lens 321 and a cemented lens of the negative lens 322 and the positive lens 323. , Surfaces U8 to U12. Similarly to the third lens group 30, the third lens group 330 includes a positive lens 331 located in the vicinity of the image side on the optical axis O3 of the aperture stop D3 in order along the optical axis O3 from the object side to the image plane IMG side. And has surfaces U14 and U15 together with the surface U13 of the aperture stop D3.

  The fourth lens group 340 is a cemented joint of a positive lens 341 and a negative lens 342 having a concave surface (surface U20) facing the image side on the optical axis O3 in order from the object side to the image plane IMG side along the optical axis O3. And a plastic meniscus lens 343 which is a positive lens having a concave surface (surface U20) facing the image side on the optical axis O3. In order from the object side to the image plane IMG side along the optical axis O3, the positive lens 341 and the negative lens 342 have surfaces U16 to U18, and the meniscus lens 343 has surfaces U19 and U20.

  The fifth lens group 250 is configured to include only at least one aspherical positive lens 351. The positive lens 351 has surfaces U21 and U22 in order along the optical axis O3 from the object side to the image plane IMG side. The low-pass filter 361 has surfaces U23 and U24 in order along the optical axis O3 from the object side to the image plane IMG side. The cover glass 362 has surfaces U25 and U26 in order along the optical axis O3 from the object side to the image plane IMG side.

  The shape of each aspheric surface of the lens satisfies the above formula (5). Further, when f1 is the focal length of the first lens group 310, f11 is the focal length of the negative lens 311, f12 is the focal length of the positive lens 312 and fw is the focal length of the zoom lens 3 at the wide angle end, The one lens group 210 satisfies the above formulas (1), (2), and (3). Further, when ndp is the refractive index at the d-line of the prism 313, the prism 313 satisfies the above formula (4).

  According to the present embodiment, the second lens group 320 includes the negative lens 321 and the cemented lens of the negative lens 322 and the positive lens 323, thereby effectively correcting off-axis chromatic aberration in the entire zooming range. it can. In addition, the fourth lens group 340 having a relatively large refractive power in the lens group includes two positive lenses 341 and 343, thereby suppressing the occurrence of spherical aberration, coma aberration, and field curvature. Can do.

  In addition, by always fixing the position of the third lens group 330 in the optical axis O3 direction during zooming and focusing, the optical system driving unit 105 of the digital still camera 100 can be simplified, and the digital still camera 100 can be simplified. The thickness in the thickness direction can be reduced.

  In addition, by arranging the aperture stop D3 on the object side of the third lens group 330, the entrance pupil position can be brought closer to the object side on the optical axis O3, and the most object on the optical axis O3 of the first lens group 310. The diameter of the positive lens 312 on the side and the prism 313 can be reduced, so that the thickness of the digital still camera 100 in the thickness direction can be reduced. Further, the third lens group 330 is made close to the aperture stop D3 and is constituted by a positive lens 331 as a single lens, so that a space for moving the second lens group 320 and the fourth lens group 340 is secured, and spherical aberration is ensured. The coma aberration and the curvature of field can be effectively corrected.

  Further, by configuring the first lens group 310 by the negative lens 311, the prism 313, and the positive lens 312 in order from the object side along the optical axis O 3, the diameter of the light beam incident on the prism 313 is reduced. The prism 313 can be reduced in size, and the thickness in the thickness direction of the digital still camera 100 on which the zoom lens 3 is mounted can be reduced.

  Further, in the above formula (1), when f1 / fw exceeds the lower limit (2.0), the refractive power of the first lens group 310 does not become too strong, and the occurrence of aberrations occurring in the first lens group 310 is suppressed. Can do. In addition, when f1 / fw is less than the upper limit (4.5), the refractive power of the first lens group 310 is increased, thereby reducing the amount of movement of the second lens group 320 that is a variable power group, and thus the zoom lens 3. Can be shortened. Moreover, it is desirable to satisfy the range of the above formula (1 ') because the above effect is further enhanced.

  In the above formula (2), when | f11 | / fw exceeds the lower limit (1.0), it is possible to suppress the occurrence of distortion occurring in the negative lens 311. Further, when | f11 | / fw is less than the upper limit (5.0), the diameter of the light beam incident on the prism 313 can be reduced, thereby reducing the size of the prism 313 for bending the optical path. The thickness in the thickness direction of the mounted digital still camera 100 can be reduced. Moreover, it is desirable to satisfy the range of the above formula (2 ′) because the above effect is further enhanced.

  Further, in the above formula (3), when f12 / fw exceeds the lower limit (1.0), the refractive power of the positive lens 312 does not become too strong, and the occurrence of spherical aberration or the like that occurs in the positive lens 312 can be suppressed. . In addition, when f12 / fw is less than the upper limit (4.0), the refractive power of the positive lens 312 becomes strong, thereby reducing the amount of movement of the second lens group 320 that is a variable power group, and thus the total length of the zoom lens 3. Can be shortened. Further, distortion aberration generated in the negative lens 311 can be corrected. Moreover, it is desirable to satisfy the range of the above formula (3 ′) because the above effect is further enhanced.

  Further, by forming the fifth lens group 350 with one positive lens 351 having at least one aspherical shape, field curvature and distortion can be effectively corrected, and a good image can be obtained. Side telecentric characteristics can be obtained. Here, it is desirable that one positive lens 351 constituting the fifth lens group 350 is a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

  Further, by configuring the reflecting optical element with the prism 313, the diameter of the light beam passing through the prism 313 is reduced by refraction at the incident surface of the prism 313, so that the prism 313 can be reduced in size and the zoom lens 3 is mounted. The thickness of the digital still camera 100 in the thickness direction can be reduced.

  In the above formula (4), when ndp exceeds the lower limit (1.6), the diameter of the light beam passing through the prism 313 is reduced, so that the prism 313 can be reduced in size, and the thickness in the thickness direction of the digital still camera 100 is reduced. be able to. Further, it is desirable to satisfy the range of the above formula (4 ′) because the above effect is further enhanced.

  In addition, a small digital still camera 100 equipped with the zoom lens 3 can be obtained.

(Fourth embodiment)
A fourth embodiment according to the present invention will be described with reference to FIG. The device configuration of the present embodiment is obtained by replacing the configuration of the fourth lens group in the zoom lens 2 described in the second embodiment with a fourth lens group 440 described later. A configuration different from the embodiment will be mainly described.

  FIG. 5 shows a configuration of the zoom lens 4 included in the optical system 101. The zoom lens 4 includes a first lens group 410 having a positive refractive power, a second lens group 420 having a negative refractive power, an aperture stop D4, in order from the object side to the image plane IMG side along the optical axis O4. A third lens group 430 having a positive refractive power, a fourth lens group 440 having a positive refractive power, a fifth lens group 450 having a positive refractive power, a low-pass filter 461, and a cover glass 462. Is done. Instead of the low pass filter 461, an infrared cut filter may be provided.

  When the zoom lens 4 is zoomed and focused from the wide-angle end to the telephoto end, the positions of the first lens group 410, the third lens group 430, the fifth lens group 450, and the aperture stop D4 on the optical axis O4 are not changed. Yes, the second lens group 420 and the fourth lens group 440 move on the optical axis O4. Similarly to the second lens group 210 of the zoom lens 2, the first lens group 410 includes a negative lens 411, a prism 413, and a positive lens 412 in order along the optical axis O4 from the object side to the image plane IMG side. And has faces V1 to V7. Similar to the second lens group 220, the second lens group 420 includes, in order from the object side to the image plane IMG side along the optical axis O4, a negative lens 421 and a cemented lens of the positive lens 422, and surfaces V8 to V10. Have Similarly to the third lens group 230, the third lens group 430 includes, in order along the optical axis O4 from the object side to the image plane IMG side, a positive lens 431 positioned in the vicinity of the image side on the optical axis O4 of the aperture stop D4. And has surfaces V12 and V13 together with the surface V11 of the aperture stop D4.

  The fourth lens group 440 includes, in order along the optical axis O4 from the object side to the image plane IMG side, a cemented lens in which the positive lens 442 and the negative lens 443 are cemented, and the image side in the optical axis O4 direction. And a plastic meniscus lens 444 having a concave surface (surface V20). In order from the object side to the image plane IMG side along the optical axis O4, the positive lens 441 has surfaces V14 and V15, the positive lens 442 and the negative lens 443 have surfaces V16 to V18, and the meniscus lens 444 has a surface V19. , V20.

  The fifth lens group 450 includes only at least one aspherical positive lens 451. The positive lens 451 has surfaces V21 and V22 in order along the optical axis O4 from the object side to the image plane IMG side. The low pass filter 461 has surfaces V22 and V23 in order along the optical axis O4 from the object side to the image plane IMG side. The cover glass 462 has surfaces V25 and V26 in order along the optical axis O4 from the object side to the image plane IMG side.

  The shape of each aspheric surface of the lens satisfies the above formula (5). Further, when f1 is the focal length of the first lens group 410, f11 is the focal length of the negative lens 411, f12 is the focal length of the positive lens 412, and fw is the focal length of the zoom lens 4 at the wide angle end, The one lens group 410 satisfies the above expressions (1), (2), and (3). Further, when ndp is the refractive index at the d-line of the prism 413, the prism 413 satisfies the above formula (4).

  According to the present embodiment, the second lens group 420 is configured only by the cemented lens of the negative lens 421 and the positive lens 422, so that the amount of movement of the second lens group 420 can be efficiently reduced while suppressing the occurrence of chromatic aberration. It is easy to ensure the zoom ratio of the zoom lens 4. In addition, the fourth lens group 440 having a relatively large refractive power in the lens group includes two positive lenses 441 and 442, thereby suppressing the occurrence of spherical aberration, coma aberration, and field curvature. Can do.

  In addition, by always fixing the position of the third lens group 430 in the optical axis O4 direction during zooming and focusing, the optical system driving unit 105 of the digital still camera 100 can be simplified, and the digital still camera 100 can be simplified. The thickness in the thickness direction can be reduced.

  Further, by arranging the aperture stop D4 on the object side of the third lens group 430, the entrance pupil position can be brought closer to the object side on the optical axis O4, and the most object on the optical axis O4 of the first lens group 410. The diameter of the positive lens 412 on the side and the prism 413 can be reduced, so that the thickness of the digital still camera 100 in the thickness direction can be reduced. Further, the third lens group 430 is made close to the aperture stop D4 and is constituted by the positive lens 431 as a single lens, so that a space for moving the second lens group 420 and the fourth lens group 440 is secured, and spherical aberration is achieved. The coma aberration and the curvature of field can be effectively corrected.

  Further, by configuring the first lens group 410 by the negative lens 411, the prism 413, and the positive lens 412 in order from the object side along the optical axis O4, the diameter of the light beam incident on the prism 413 is reduced. The prism 413 can be reduced in size, and the thickness in the thickness direction of the digital still camera 100 on which the zoom lens 4 is mounted can be reduced.

  Further, in the above formula (1), when f1 / fw exceeds the lower limit (2.0), the refractive power of the first lens group 410 does not become too strong, and the occurrence of aberrations occurring in the first lens group 410 is suppressed. Can do. In addition, when f1 / fw is less than the upper limit (4.5), the refractive power of the first lens group 410 becomes strong, whereby the amount of movement of the second lens group 420, which is a variable power group, can be reduced. Can be shortened. Moreover, it is desirable to satisfy the range of the above formula (1 ') because the above effect is further enhanced.

  Further, in the above formula (2), when | f11 | / fw exceeds the lower limit (1.0), it is possible to suppress the occurrence of distortion occurring in the negative lens 411. In addition, when | f11 | / fw is less than the upper limit (5.0), the diameter of the light beam incident on the prism 413 can be reduced, thereby reducing the size of the prism 413 for bending the optical path. The thickness in the thickness direction of the mounted digital still camera 100 can be reduced. Moreover, it is desirable to satisfy the range of the above formula (2 ′) because the above effect is further enhanced.

  Further, in the above formula (3), when f12 / fw exceeds the lower limit (1.0), the refractive power of the positive lens 412 does not become too strong, and the occurrence of spherical aberration or the like that occurs in the positive lens 412 can be suppressed. . Further, when f12 / fw is less than the upper limit (4.0), the refractive power of the positive lens 412 becomes strong, and thereby the movement amount of the second lens group 420 which is a variable power group can be reduced. Can be shortened. Further, distortion aberration generated in the negative lens 411 can be corrected. Moreover, it is desirable to satisfy the range of the above formula (3 ′) because the above effect is further enhanced.

  Further, by configuring the fifth lens group 450 with a single positive lens 451 having an aspherical shape, it is possible to effectively correct field curvature and distortion, and to achieve good image side telecentric characteristics. Obtainable. Here, the single positive lens 451 constituting the fifth lens group 450 is desirably a lens having a stronger positive refractive power on the image side. By adopting such a shape, the image side telecentric characteristics can be made particularly good while minimizing the influence on spherical aberration and coma.

  In addition, since the reflecting optical element is constituted by the prism 413, the diameter of the light beam passing through the prism 413 is reduced by refraction at the incident surface of the prism 413, so that the prism 413 can be reduced in size and the zoom lens 4 is mounted. The thickness of the digital still camera 100 in the thickness direction can be reduced.

  In the above formula (4), when ndp exceeds the lower limit (1.6), the diameter of the light beam passing through the prism 413 is reduced, so that the prism 413 can be reduced in size and the thickness of the digital still camera 100 in the thickness direction is reduced. be able to. Further, it is desirable to satisfy the range of the above formula (4 ′) because the above effect is further enhanced.

  In addition, a small digital still camera 100 equipped with the zoom lens 4 can be obtained.

A specific example 1 according to the first embodiment will be described. The zoom lens 1 of the present example satisfies the following Table 1.

  In Table 1 (a) above, ri: radius of curvature at the surface Si (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O1 or its gap length), ndi: di The refractive index of the part, νdi: Abbe number of the di part. On the optical axis O1, the distance between the surfaces Sj and S (j + 1) is dj (where j is an arbitrary number of i).

  In Table 1 (b), the aspheric coefficients of the fourteenth surface S14, the twenty-first surface S21, the twenty-second surface S22, the twenty-third surface S23, and the twenty-fourth surface S24 are the coefficients of the above equation (5). Show. In Table 1 (c), the values of the lengths d7, d12, d15, and d22 when the focal length f of the zoom lens 1 is changed to 6.49 mm, 10.93 mm, and 18.50 mm are shown. The field angles of the zoom lens 1 corresponding to the focal lengths f = 6.49 mm, 10.93 mm, and 18.50 mm are the field angles 2ω = 61.8 °, 36.6 °, and 21.8 °, respectively.

Further, Table 2 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment.

  As shown in Table 2, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment are sequentially expressed by the above formula (1 ′), formula (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 6A shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of the present example at the focal length f = 6.49 mm. FIG. 6B shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of the present example at the focal length f = 10.93 mm. FIG. 6C shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present embodiment at the focal length f = 18.50 mm. As shown in FIGS. 6A, 6B, and 6C, according to the zoom lens 1 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 2 according to the second embodiment will be described. The zoom lens 2 of the present example satisfies the following Table 3.

  In Table 3 (a) above, ri: radius of curvature at the surface Ti (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O2 or its gap length), ndi: di The refractive index of the part, νdi: Abbe number of the di part. On the optical axis O2, the distance between the surfaces Tj and T (j + 1) is dj (where j is an arbitrary number of i).

  In Table 3 (b), the aspheric coefficients of the seventh surface T7, the eighth surface T8, the twelfth surface T12, and the thirteenth surface T13 indicate the coefficients of the above equation (5). In Table 2 (c), the values of the lengths d7, d10, d13, and d18 when the focal length f of the zoom lens 2 is changed to 6.30 mm, 10.60 mm, and 17.90 mm are shown. In addition, the field angles of the zoom lens 2 corresponding to the focal lengths f = 6.30 mm, 10.60 mm, and 17.90 mm are the field angle 2ω = 63.4 °, 37.8 °, and 22.8 °, respectively.

Table 4 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 2 of the present embodiment.

  As shown in Table 4, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 2 of the present embodiment are sequentially expressed by the above formula (1 ′), formula (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 7A shows the spherical aberration, astigmatism, and distortion of the zoom lens 2 of the present example at the focal length f = 6.30 mm. FIG. 7B shows spherical aberration, astigmatism, and distortion of the zoom lens 2 of the present embodiment at the focal length f = 10.60 mm. FIG. 7C shows the spherical aberration, astigmatism and distortion of the zoom lens 2 of the present embodiment at the focal length f = 17.90 mm. As shown in FIGS. 7A, 7B, and 7C, according to the zoom lens 2 of the present embodiment, the spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 3 according to the third embodiment will be described. The zoom lens 3 of the present example satisfies the following Table 5.

  In Table 5 (a) above, ri: radius of curvature at the surface Ui (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O3 or its gap length), ndi: di The refractive index of the part, νdi: Abbe number of the di part. On the optical axis O3, the distance between the surface Uj and U (j + 1) is dj (where j is an arbitrary number of i).

  In Table 5 (b), the aspheric coefficients of the seventh surface U7, the nineteenth surface U19, the twentieth surface U20, the twenty-first surface U21, and the twenty-second surface U22 are the coefficients of the above equation (5). Show. Table 5 (c) shows the values of the lengths d7, d12, d15, and d20 when the focal length f of the zoom lens 3 is changed to 6.25 mm, 11.17 mm, and 17.94 mm. In addition, the field angles of the zoom lens 3 corresponding to the focal lengths f = 6.25 mm, 11.17 mm, and 17.94 mm are the field angles 2ω = 62.6 °, 35.0 °, and 22.0 °, respectively.

Table 6 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 3 of the present embodiment.

  As shown in Table 6, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 3 of the present embodiment are sequentially expressed by the above formulas (1 ′), (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 8A shows the spherical aberration, astigmatism and distortion of the zoom lens 3 of the present example at the focal length f = 6.25 mm. FIG. 8B shows spherical aberration, astigmatism, and distortion of the zoom lens 3 of the present example at the focal length f = 11.17 mm. FIG. 8C shows the spherical aberration, astigmatism, and distortion of the zoom lens 3 of the present example at the focal length f = 17.94 mm. As shown in FIGS. 8A, 8B, and 8C, according to the zoom lens 3 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 4 according to the first embodiment will be described. The zoom lens 1 of the present example satisfies the following Table 7.

  In Table 7 (a), the radius of curvature ri, the distance di, the refractive index ndi, and the Abbe number νdi are shown as in the first embodiment.

  In Table 7 (b), the aspheric coefficients of the sixth surface S6, the fourteenth surface S14, the twenty-second surface S22, the twenty-third surface S23, and the twenty-fourth surface S24 are the coefficients of the above equation (5). Show. In Table 7 (c), the values of the lengths d7, d12, d15, and d22 when the focal length f of the zoom lens 1 is changed to 6.49 mm, 11.17 mm, and 17.94 mm are shown. In addition, the field angles of the zoom lens 1 corresponding to the focal lengths f = 6.49 mm, 11.17 mm, and 17.94 mm are the field angles 2ω = 60.4 °, 35.8 °, and 21.4 °, respectively.

Table 8 shows the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment.

  As shown in Table 8, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment are sequentially expressed by the above formulas (1 ′), (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 9A shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of the present example at the focal length f = 6.49 mm. FIG. 9B shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present embodiment at the focal length f = 11.17 mm. FIG. 9C shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present embodiment at the focal length f = 17.94 mm. As shown in FIGS. 9A, 9B, and 9C, according to the zoom lens 1 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 5 according to the third embodiment will be described. The zoom lens 3 of the present example satisfies the following Table 9.

  In Table 9 (a), similarly to Example 1, the radius of curvature ri, the distance di, the refractive index ndi, and the Abbe number νdi are shown.

  In Table 9 (b), the aspheric coefficients of the fourteenth surface U14, the nineteenth surface U19, the twentieth surface U20, the twenty-first surface U21, and the twenty-second surface U22 are the coefficients of the above equation (5). Show. In Table 9 (c), the values of lengths d7, d12, d15, and d20 when the focal length f of the zoom lens 3 is changed to 6.49 mm, 14.33 mm, and 18.52 mm are shown. In addition, the field angles of the zoom lens 3 corresponding to the focal lengths f = 6.49 mm, 14.33 mm, and 18.52 mm are the field angles 2ω = 60.6 °, 27.4 °, and 21.4 °, respectively.

Table 10 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 3 of the present embodiment.

  As shown in Table 10, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 3 of the present embodiment are sequentially expressed by the above formula (1 ′), formula (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 10A shows the spherical aberration, astigmatism and distortion of the zoom lens 3 of the present example at the focal length f = 6.49 mm. FIG. 10B shows the spherical aberration, astigmatism and distortion of the zoom lens 3 of the present example at the focal length f = 14.33 mm. FIG. 11C shows the spherical aberration, astigmatism and distortion of the zoom lens 3 of the present example at the focal length f = 18.52 mm. As shown in FIGS. 10A, 10B, and 10C, according to the zoom lens 3 of the present embodiment, the spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 6 according to the fourth embodiment will be described. The zoom lens 4 of this embodiment satisfies the following Table 11.

  In Table 11 (a) above, ri: radius of curvature at the surface Vi (i: number) of the optical element, di: distance [mm] (the thickness of the optical element on the optical axis O4 or its gap length), ndi: di The refractive index of the part, νdi: Abbe number of the di part. On the optical axis O4, the distance between the surfaces Vj and V (j + 1) is dj (where j is an arbitrary number of i).

  In Table 11 (b), the aspheric coefficients of the nineteenth surface V19, the twentieth surface V20, the twenty-first surface V21, and the twenty-second surface V22 indicate the coefficients of the above equation (5). In Table 11 (c), the values of the lengths d7, d10, d13, and d20 when the focal length f of the zoom lens 4 is changed to 6.49 mm, 10.95 mm, and 18.49 mm are shown. In addition, the field angles of the zoom lens 4 corresponding to the focal lengths f = 6.49 mm, 10.95 mm, and 18.49 mm are the field angles 2ω = 60.4 °, 35.4 °, and 21.2 °, respectively.

Table 12 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 4 of the present embodiment.

  As shown in Table 12, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 4 of the present embodiment are sequentially expressed by the above formulas (1 ′), (2 ′), Expressions (3 ′) and (4 ′) are satisfied.

  FIG. 11A shows the spherical aberration, astigmatism and distortion of the zoom lens 4 of the present embodiment at the focal length f = 6.49 mm. FIG. 11B shows the spherical aberration, astigmatism, and distortion of the zoom lens 4 of the present example at the focal length f = 10.95 mm. FIG. 11C shows the spherical aberration, astigmatism and distortion of the zoom lens 4 of the present example at the focal length f = 18.49 mm. As shown in FIGS. 11A, 11B, and 11C, according to the zoom lens 4 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

A specific example 7 according to the first embodiment will be described. The zoom lens 1 of the present example satisfies the following Table 13.

  In Table 13 (a), as in Example 1, the radius of curvature ri, the distance di, the refractive index ndi, and the Abbe number νdi are shown.

  In Table 13 (b), the aspheric coefficients of the fourteenth surface S14, the twenty-first surface S21, the twenty-second surface S22, the twenty-third surface S23, and the twenty-fourth surface S24 are the coefficients of the above equation (5). Show. Table 13 (c) shows the values of lengths d7, d12, d15, and d22 when the focal length f of the zoom lens 1 is changed to 6.49 mm, 14.28 mm, and 18.5 mm. The field angles of the zoom lens 1 corresponding to the focal lengths f = 6.49 mm, 14.28 mm, and 18.5 mm are the field angles 2ω = 60.6 °, 27.6 °, and 21.4 °, respectively.

Table 14 shows values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment.

  As shown in Table 14, the values of f1 / fw, | f11 | / fw, f12 / fw, and ndp in the zoom lens 1 of the present embodiment are sequentially expressed by the above formula (1 ′), formula (2 ′), Expressions (3 ′) and (4) are satisfied.

  FIG. 12A shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present example at the focal length f = 6.49 mm. FIG. 12B shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present example at the focal length f = 14.28 mm. FIG. 12C shows the spherical aberration, astigmatism and distortion of the zoom lens 1 of the present example at the focal length f = 18.5 mm. As shown in FIGS. 12A, 12B, and 12C, according to the zoom lens 1 of the present embodiment, spherical aberration, astigmatism, and distortion are excellent even when the focal length f is changed. Can be corrected.

  Note that the description in each of the above embodiments and examples is an example of a preferable zoom lens and imaging apparatus according to the present invention, and the present invention is not limited to this.

  For example, in each of the above embodiments and examples, an example of a digital still camera has been described as an image pickup apparatus equipped with a zoom lens. However, the present invention is not limited to this, and a video camera or a mobile phone with an image pickup function is described. It may be a device such as a portable terminal having at least an imaging function, such as PHS (Personal Handyphone System) and PDA (Personal Digital Assistant).

  In addition, an imaging device equipped with a zoom lens may be used as an imaging unit installed in the device. Here, with reference to FIG. 13, an example of a mobile phone 500 equipped with an imaging unit 550 as an imaging device will be described. FIG. 13 shows an internal configuration of the mobile phone 500.

  As shown in FIG. 13, the mobile phone 500 has a control unit (CPU) 510 that performs overall control of each unit and executes a program corresponding to each process, and an operation unit 520 for operating and inputting numbers and the like with keys. A display unit 530 for displaying captured images in addition to predetermined data, a wireless communication unit 540 for realizing various information communication with an external server or the like via the antenna 541, and an imaging device An imaging unit 550, a storage unit (ROM) 560 storing necessary data such as a system program and various processing programs and a terminal ID of the mobile phone 500, and various processing programs and data executed by the control unit 510; Alternatively, processing data or used as a work area for temporarily storing imaging data or the like by the imaging unit 550 and temporary storage (RAM) and a 570.

  The imaging unit 550 includes the zoom lens 1 according to the first embodiment, the zoom lens 2 according to the second embodiment, the zoom lens 3 according to the third embodiment, or the zoom lens 4 according to the fourth embodiment. (Solid) An imaging element, a lens barrel, a drive mechanism for zoom lenses 1, 2, 3 or 4, and the like. The lens unit is assumed to be coupled to a control unit, an operation unit, a display unit, and the like. Specifically, in the imaging unit 550, for example, the object-side end surface of the housing in the imaging optical system is provided on the back surface of the mobile phone 500 (the main display portion of the display portion 530 is the front surface), and below the main display portion. Is disposed at a position corresponding to. The external connection terminal of the imaging unit 550 is connected to the control unit 510 of the mobile phone 500 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 510 side. Further, the image signal input from the imaging unit 550 is stored in the storage unit 560 or displayed on the display unit 530 by the control system of the mobile phone 500, and further, as video information via the wireless communication unit 540. Sent to the outside.

  An imaging unit as an imaging device equipped with a zoom lens includes the lens unit, a control unit, an image processing unit, and the like disposed on a substrate, and includes a display unit, an operation unit, and the like using connectors. You may comprise as a camera module on the assumption that it is couple | bonded and used separately.

  Further, in each of the above embodiments and examples, the configuration using the prism as the reflective optical element has been described. However, the present invention is not limited to this, and a configuration using another reflective optical element such as a mirror may be used. .

  Moreover, it is good also as combining said each embodiment and each Example suitably.

1 is a diagram illustrating an internal configuration of a digital still camera 100 according to a first embodiment of the present invention. 1 is a diagram illustrating a configuration of a zoom lens 1 included in an optical system 101. FIG. 1 is a diagram illustrating a configuration of a zoom lens 2 included in an optical system 101. FIG. 2 is a diagram illustrating a configuration of a zoom lens 3 included in an optical system 101. FIG. 2 is a diagram illustrating a configuration of a zoom lens 4 included in an optical system 101. FIG. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of Example 1 in the focal distance f = 6.49mm. (B) is a diagram showing the spherical aberration, astigmatism, and distortion of the zoom lens 1 of Example 1 at a focal length f = 10.93 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 1 of Example 1 at the focal length f = 18.50 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 2 of Example 2 in the focal distance f = 6.30mm. (B) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 2 of Example 2 at the focal length f = 10.60 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 2 of Example 2 at a focal length f = 17.90 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 3 of Example 3 in the focal distance f = 6.25mm. (B) is a diagram showing the spherical aberration, astigmatism, and distortion of the zoom lens 3 of Example 3 at a focal length f = 11.17 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 3 of Example 3 at the focal length f = 17.94 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of Example 4 in the focal distance f = 6.49mm. (B) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 1 of Example 4 at the focal length f = 11.17 mm. (C) is a diagram showing the spherical aberration, astigmatism, and distortion of the zoom lens 1 of Example 4 at the focal length f = 17.94 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 3 of Example 5 in the focal distance f = 6.49mm. (B) is a diagram showing the spherical aberration, astigmatism, and distortion of the zoom lens 3 of Example 5 at the focal length f = 14.33 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 3 of Example 5 at the focal length f = 18.52 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 4 of Example 6 in the focal distance f = 6.49mm. (B) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 4 of Example 6 at the focal length f = 10.105 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 4 of the present embodiment at the focal length f = 18.49 mm. (A) is a figure which shows the spherical aberration, astigmatism, and distortion of the zoom lens 1 of Example 7 in the focal distance f = 6.49mm. (B) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 1 of Example 7 at the focal length f = 14.28 mm. (C) is a diagram showing the spherical aberration, astigmatism and distortion of the zoom lens 1 of Example 7 at the focal length f = 18.5 mm. 4 is a block diagram showing an internal configuration of a mobile phone 500. FIG.

Explanation of symbols

O1, O2, O3, O4 Optical axis 100 Digital still camera 101 Optical system 1, 2, 3, 4 Zoom lens D1, D2, D3, D4 Aperture stop 10, 210, 310, 410 First lens group 11, 211, 311 , 411 Negative lens 13, 213, 313, 413 Prism 12, 212, 312, 412 Positive lens 20, 220, 320, 420 Second lens group 21, 321 Negative lens 22, 221, 322, 421 Negative lens 23, 222, 323,422 Positive lens 30,230,330,430 Third lens group 31,231,331,431 Positive lens 40,240,340,440 Fourth lens group 41,241,441 Positive lens 42,242,341,442 Positive lens 43,243,342,443 Negative lens 44,343,444 Meniscus lens 0, 250, 350, 450 Fifth lens group 51, 251, 351, 451 Positive lens 61, 261, 361, 461 Low pass filter 62, 262, 362, 462 Cover glass 102 Solid-state image sensor 103 A / D converter 104 Control Unit 105 optical system driving unit 106 image sensor driving unit 107 timing generation unit 108 image memory 109 image processing unit 110 image compression unit 111 image recording unit 112 display unit 113 operation unit 500 mobile phone 510 control unit 520 input unit 530 display unit 540 wireless Communication unit 541 Antenna 550 Imaging unit 560 Storage unit 570 Temporary storage unit

Claims (10)

In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The first lens group includes a reflective optical element for bending the optical path,
The second lens group includes a negative lens and a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
The fourth lens group includes at least two positive lenses, and is arranged in order from the object side along the optical axis, a cemented lens of a positive lens and a negative lens, and a concave surface on the image side on the optical axis. And a meniscus lens facing the zoom lens. In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The second lens group includes a negative lens and a cemented lens of a negative lens and a positive lens in order from the object side along the optical axis.
The fourth lens group includes at least two positive lenses,
The first lens group includes a first lens having negative refractive power in order from the object side along the optical axis, a reflective optical element for bending the optical path, and a second lens having positive refractive power. And
2.0 <f1 / fw <4.5 (1)
1.0 <| f11 | / fw <5.0 (2)
1.0 <f12 / fw <4.0 (3)
(Where f1: focal length of the first lens group, f11: focal length of the first lens, f12: focal length of the second lens, fw: focal length at the wide angle end of the zoom lens)
A zoom lens characterized by satisfying The fifth lens group, the zoom lens according to claim 1 or 2, characterized in that it consists of only one positive lens having an aspherical shape of at least one surface. In order from the object side along the optical axis,
A first lens group having a positive refractive power and whose position on the optical axis is always fixed during zooming and focusing;
A second lens group having negative refractive power;
A third lens group having positive refractive power;
A fourth lens group having a positive refractive power;
A fifth lens group,
While performing zooming by moving at least the second lens group and the fourth lens group, focusing is performed by moving at least the fourth lens group,
The second lens group includes a cemented lens of a negative lens and a positive lens,
The fourth lens group includes at least two positive lenses,
The fifth lens group, Ri Do because only one positive lens having an aspherical shape of at least one surface,
The first lens group includes a first lens having negative refractive power in order from the object side along the optical axis, a reflective optical element for bending the optical path, and a second lens having positive refractive power. And
2.0 <f1 / fw <4.5 (1)
1.0 <| f11 | / fw <5.0 (2)
1.0 <f12 / fw <4.0 (3)
(Where f1: focal length of the first lens group, f11: focal length of the first lens, f12: focal length of the second lens, fw: focal length at the wide angle end of the zoom lens)
A zoom lens characterized by satisfying The third lens group, a zoom lens according to claim 1, any one of 4, which is a position always fixed on the optical axis during zooming and focusing. An aperture stop on the object side on the optical axis of the third lens group;
The zoom lens according to any one of claims 1 to 5 , wherein the third lens group includes only one positive lens having at least one aspherical shape. The first lens group includes:
2.7 <f1 / fw <4.0 (1 ')
1.9 <| f11 | / fw <3.1 (2 ')
1.9 <f12 / fw <2.3 (3 ')
The zoom lens according to claim 2, wherein: The reflective optical element comprises a prism that bends the optical path,
ndp> 1.6 (4)
(Where ndp is the refractive index of the prism at the d-line)
The zoom lens according to any one of claims 1 to 7, characterized in that meet. The reflective optical element is
ndp> 1.84 (4 ')
The zoom lens according to claim 8 , wherein: The zoom lens according to any one of claims 1 to 9 ,
An image pickup apparatus comprising: an image pickup device that picks up light incident through the zoom lens.

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