JP2004117828A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup device which is compact in structure and less in residual chromatic aberration in spite of its being equipped with a high-performance and high-magnification zoom lens system. <P>SOLUTION: The image pickup device is equipped with the zoom lens system having a plurality of lens groups and forming the optical image of an object consecutively optically so that power can be varied by changing space between a plurality of lens groups, and an imaging device converting the optical image formed by the zoom lens system into an electrical signal. The zoom lens system is equipped with a 1st group having negative power, a 2nd group arranged through variable space on the image side of the 1st group and having positive power, and an image side group constituted of at least one lens group including a 3rd group arranged through variable space on the image side of the 2nd group in order from the object side, and at least one diffraction optical surface is provided in the zoom lens system. <P>COPYRIGHT: (C)2004,JPO

Description

以下の表１及び表２は、条件式に対する各実施例の数値を示している。
【００５１】
【表１】

【００５２】
【表２】

【００５３】
図６乃至図１０は実施例１〜実施例５の収差図であり、各実施例のズームレンズ系の無限遠合焦状態での収差を表している。図５乃至図１０中、それぞれ上から順に、最短焦点距離状態，中間焦点距離状態，最長焦点距離状態での諸収差を示している。各焦点距離状態での収差図は、左から順に、球面収差，非点収差，歪曲収差を表している。球面収差図において、縦軸は入射瞳への入射高さＨをその最大高さＨ０（＝１）で規格化した値（すなわち入射瞳平面を切る相対高さ）Ｈ／Ｈ０であり、横軸は近軸結像位置からの光軸方向のズレ量（ｍｍ）である。実線はｄ線（波長：λｄ＝５８７．６ｎｍ）に対する球面収差量を表している。非点収差図において、縦軸は像高Ｙ’（ｍｍ）であり、横軸は近軸結像位置からの光軸方向のズレ量（ｍｍ）である。また、実線Ｘはサジタル面での非点収差を表しており、実線Ｙはメリディオナル面での非点収差を表している。歪曲収差図において、縦軸は像高Ｙ’（ｍｍ）であり、横軸は歪曲収差量（％）である。
【００５４】
【発明の効果】
以上説明したように、各実施形態のズームレンズ系によれば、高性能で高倍率ズームレンズ系を備えながら、コンパクトで残存色収差の少ない撮像装置を提供することができる。
【図面の簡単な説明】
【図１】第１の実施形態（実施例１）のレンズ構成図。
【図２】第２の実施形態（実施例２）のレンズ構成図。
【図３】第３の実施形態（実施例３）のレンズ構成図。
【図４】第４の実施形態（実施例４）のレンズ構成図。
【図５】第５の実施形態（実施例５）のレンズ構成図。
【図６】実施例１の無限遠合焦状態での収差図。
【図７】実施例２の無限遠合焦状態での収差図。
【図８】実施例３の無限遠合焦状態での収差図。
【図９】実施例４の無限遠合焦状態での収差図。
【図１０】実施例５の無限遠合焦状態での収差図。
【図１１】本発明の概略を示す構成図。
【符号の説明】
ＬＰＦ：光学的ローパスフィルタに相当する平行平面板
ＳＲ：固体撮像素子
ＴＬ：ズームレンズ系
Ｇｒ１：第１レンズ群Ｇｒ１
Ｇｒ２：第２レンズ群Ｇｒ２
Ｇｒ３：第３レンズ群Ｇｒ３
ＳＴ：絞り[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device that converts an optical image formed on a light receiving surface such as a CCD (Charge Coupled Device) or a CMOS sensor (Complementary Metal-oxide Semiconductor) into an electric signal. More particularly, the present invention relates to an imaging device that is a main component of a camera built in or external to a digital camera; a personal computer, a mobile computer, a mobile phone, a personal digital assistant (PDA), or the like. More specifically, the present invention particularly relates to a small-sized imaging device having a zoom lens system.
[0002]
[Prior art]
In recent years, digital cameras that convert an optical image into an electric signal using a solid-state imaging device such as a CCD or a CMOS sensor instead of a silver halide film, digitize the data, and record or transfer the data have been rapidly spreading. ing. In such digital cameras, recently, CCDs and CMOS sensors having high pixels such as 2 million pixels and 3 million pixels have been provided at relatively low cost. The demand for a high-performance imaging device has been greatly increased. In particular, a compact imaging device equipped with a zoom lens system capable of zooming without deteriorating the image quality has been desired. In the past, the term digital camera used to refer exclusively to those that record optical still images, but those that can simultaneously handle moving pictures and digital video cameras for home use have also been proposed, and at present there is no particular distinction between them. It is getting better. Therefore, hereinafter, the term digital camera mainly refers to an imaging device having a solid-state imaging device that converts an optical image formed on a light receiving surface of a solid-state imaging device such as a digital still camera or a digital movie into an electric signal. And all cameras that do so.
[0003]
Further, in recent years, with the improvement of image processing capability of semiconductor elements and the like, an imaging device has been built in or externally attached to a personal computer, a mobile computer, a mobile phone, a personal digital assistant (PDA), and the like. This has spurred demand for high-performance imaging devices.
[0004]
As a zoom lens system used in such an image pickup apparatus, many so-called minus-lead zoom lens systems have been proposed in which the lens group arranged closest to the object side has negative power. The minus lead zoom lens system has features such as easy widening of the angle and easy securing of a lens back necessary for insertion of an optical low-pass filter.
[0005]
As a minus lead zoom lens system, there is a zoom lens system conventionally proposed as a photographing lens system of a camera for a silver halide film. However, these zoom lens systems are provided corresponding to each pixel of the solid-state imaging device having a high number of pixels, particularly since the exit pupil position of the lens system in the shortest focal length state is relatively close to the image plane. There is a problem that the pupil does not match with the pupil of the obtained micro lens, and the peripheral light amount cannot be sufficiently secured. In addition, since the exit pupil position fluctuates greatly at the time of zooming, there is also a problem that it is difficult to set the pupil of the micro lens. In addition, since the required optical performance such as spatial frequency characteristics is completely different between the silver halide film and the solid-state imaging device, sufficient optical performance required for the solid-state imaging device cannot be secured. For this reason, it has been necessary to develop a dedicated zoom lens system optimized for an imaging device having a solid-state imaging device.
[0006]
Further, in a high-magnification and high-quality zoom lens system for a solid-state imaging device, it is necessary to reduce residual chromatic aberration, and an expensive extraordinary dispersion lens is generally used. Further, the number of lens elements constituting a zoom group included in a zoom lens system tends to increase for color week difference correction (for example, Patent Documents 1 to 3). These publications disclose zoom lenses having a power of about 3 to 10 times and the first group having a negative power.
[0007]
[Patent Document 1]
JP-A-10-104518 [Patent Document 2]
JP-A-09-243917 [Patent Document 3]
JP-A-09-203861
[Problems to be solved by the invention]
However, the above three publications have a problem that the residual chromatic aberration is still large as a zoom lens system used for an imaging device for a high-quality digital camera.
[0009]
In view of the above problems, an object of the present invention is to provide a compact imaging apparatus having a high-performance and high-magnification zoom lens system and having small residual chromatic aberration.
[0010]
Another aspect of the present invention is a digital camera including the imaging device. In the past, the term digital camera used to refer exclusively to those that record optical still images, but those that can simultaneously handle moving pictures and digital video cameras for home use have also been proposed, and at present there is no particular distinction between them. It is getting better. Therefore, hereinafter, the term digital camera mainly refers to an imaging device having a solid-state imaging device that converts an optical image formed on a light receiving surface of a solid-state imaging device such as a digital still camera or a digital movie into an electric signal. And all cameras that do so.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an imaging apparatus according to the present invention has a plurality of lens groups, and continuously changes the optical image of an object optically by changing an interval between the plurality of lens groups. An image pickup apparatus comprising: a zoom lens system capable of being formed; and an image pickup device for converting an optical image formed by the zoom lens system into an electric signal, wherein the zoom lens system has negative power in order from the object side. A first group, a second group having a positive power disposed on the image side of the first group at a variable interval, and a third group disposed at a variable interval on the image side of the second group. And at least one diffractive optical surface in the zoom lens system.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0013]
An image pickup apparatus according to an embodiment of the present invention includes a zoom lens system, a TL, and an optical low-pass filter that form an optical image of an object in a variable order from the object side (subject side), for example, as shown in FIG. It comprises an LPF and a solid-state imaging device SR that converts an optical image formed by the zoom lens system TL into an electric signal. The imaging device is a main component of a digital camera; a video camera; a camera built in or external to a personal computer, a mobile computer, a mobile phone, a personal digital assistant (PDA), or the like.
[0014]
The zoom lens system TL includes a plurality of lens groups including a first lens group Gr1, a second lens group Gr2, and a third lens group Gr3, and changes an interval between the lens groups to form an optical image. It is possible to change the size. The first lens group Gr1 has negative power, the second lens group Gr2 has negative power, and the third lens group Gr3 has positive power.
[0015]
The optical low-pass filter LPF has a specific cutoff frequency for adjusting the spatial frequency characteristics of the taking lens system and eliminating color moiré generated in the solid-state imaging device. The optical low-pass filter of the embodiment is a birefringent low-pass filter formed by laminating a birefringent material such as quartz whose crystal axis is adjusted in a predetermined direction, a wave plate that changes the plane of polarization, and the like. Note that, as the optical low-pass filter, a phase-type low-pass filter or the like that achieves the required optical cutoff frequency characteristics by the diffraction effect may be employed.
[0016]
The solid-state imaging device SR includes a CCD having a plurality of pixels, and converts an optical image formed by the zoom lens system into an electric signal by the CCD. The signal generated by the solid-state imaging device SR is subjected to predetermined digital image processing or image compression processing as necessary, and is recorded as a digital video signal in a memory (semiconductor memory, optical disk, or the like). Or is converted to an infrared signal and transmitted to another device. Note that a CMOS sensor (Complementary Metal-oxide Semiconductor) may be used instead of the CCD.
[0017]
FIGS. 1 to 5 are configuration diagrams showing lens arrangements in a shortest focal length state of a zoom lens system included in the imaging apparatuses of the first to fifth embodiments of the present invention. In each of the drawings, a parallel plate closest to the image side represents a filter including an optical low-pass filter.
[0018]
The zoom lens system according to the first embodiment shown in FIG. 1 includes, in order from the object side, a first unit Gr1 having negative power, a second unit Gr2 having positive power, and a third unit Gr3 having positive power. During zooming from the shortest focal length state to the longest focal length state, the first lens unit Gr1 moves while drawing a locus convex toward the image side and then toward the object side, and The group Gr2 moves to the object side, while the third group Gr3 is fixed with respect to the image plane.
[0019]
The zoom lens system according to the second embodiment shown in FIG. 2 includes, in order from the object side, a first unit Gr1 having negative power, a second unit Gr2 having positive power, and a third unit Gr3 having negative power. , The fourth unit Gr4 having a positive power. The first unit Gr1 is convex on the image side and then on the object side at the time of zooming from the shortest focal length state to the longest focal length state. The second unit Gr2 and the third unit Gr3 move toward the object side while the fourth unit Gr4 is fixed with respect to the image plane.
[0020]
The zoom lens system according to the third embodiment shown in FIG. 3 includes, in order from the object side, a first unit Gr1 having negative power, a second unit Gr2 having positive power, and a third unit Gr3 having negative power. , A fourth lens unit Gr4 having a positive power, and a fifth lens unit Gr5 having a positive power. The first lens unit Gr1 temporarily stores an image during zooming from the shortest focal length state to the longest focal length state. The second group Gr2, the third group Gr3, and the fourth group Gr4 move toward the object side while drawing a locus convex toward the object side, and then move toward the object side, while the fifth group Gr5 moves relative to the image plane. Fixed.
[0021]
The zoom lens system according to the fourth embodiment shown in FIG. 4 includes, in order from the object side, a first unit Gr1 having negative power, a second unit Gr2 having positive power, and a third unit Gr3 having positive power. , A fourth lens unit Gr4 having a negative power, and a fifth lens unit Gr5 having a positive power. The first lens unit Gr1 temporarily stores an image during zooming from the shortest focal length state to the longest focal length state. The second group Gr2, the third group Gr3, and the fourth group Gr4 move toward the object side while drawing a locus convex toward the object side, and then move toward the object side, while the fifth group Gr5 moves relative to the image plane. Fixed.
[0022]
The zoom lens system according to the fifth embodiment shown in FIG. 5 includes, in order from the object side, a first unit Gr1 having negative power, a second unit Gr2 having positive power, and a third unit Gr3 having positive power. , A fourth lens unit Gr4 having a positive power, and a fifth lens unit Gr5 having a positive power. The first lens unit Gr1 temporarily stores an image during zooming from the shortest focal length state to the longest focal length state. The second group Gr2, the third group Gr3, and the fourth group Gr4 move toward the object side while drawing a locus convex toward the object side, and then move toward the object side, while the fifth group Gr5 moves relative to the image plane. Fixed.
[0023]
In each of the zoom lens systems according to the embodiments, the stop ST is disposed between the first group Gr1 and the second group Gr2. The parallel plate closest to the image side represents a filter LPF including an optical low-pass filter.
[0024]
The zoom lens system according to each embodiment includes one diffractive optical surface in each lens group. In general, axial chromatic aberration generated on a certain surface of an optical system including a diffractive optical element is expressed by the following equation when handled in a thin-walled system.
[0025]
L = φre / νre + φde / νde (a)
νre = (Nd−1) / (Nf−Nc) (b)
νde = λd / (λf−λc) = − 3.45 (c)
However,
L: axial chromatic aberration,
φre: power of refractive optical element,
νre: dispersion value (Abbe number) of the refractive optical element,
φde: power of the diffractive optical element,
νde: dispersion value of the diffractive optical element,
Nd: refractive index on the lens optical axis of the refractive optical element with respect to the d line,
Nf: refractive index on the lens optical axis of the refractive optical element with respect to the f-line,
Nc: refractive index on the lens optical axis of the refractive optical element for c-line,
λd: wavelength of d-line,
λf: wavelength of f-line,
λc: wavelength of c-line,
It is.
[0026]
In a conventional optical system composed only of a refractive optical surface, the second term of the above equation (a) does not exist, and the dispersion value νre can take only a positive value in the refractive optical surface. The only way to cancel the chromatic aberration L is to dispose a surface with the opposite sign on the optical path. For this reason, the number of lenses has inevitably increased to correct axial chromatic aberration.
[0027]
However, as can be confirmed from the expression (c), in the optical system including the diffractive optical surface, the second term in the expression (a) is present, and the dispersion value νde of the diffractive optical surface has a large negative value. The axial chromatic aberration can be reduced only by combining a refractive optical surface having a positive power with a diffractive optical surface having a positive power. In particular, by using a diffraction-refraction hybrid type lens element in which a diffraction pattern is provided on a refraction surface, axial chromatic aberration can be corrected without increasing the number of lenses.
[0028]
In the zoom lens system according to each embodiment, a zoom lens system having a small number of lenses while achieving high magnification and high image quality is achieved by effectively arranging the above-described diffraction-refraction Hybrid type lens elements.
[0029]
Next, the range of conditional expressions that should be satisfied by the zoom lens system of each embodiment will be described. It is desirable that all of the conditional expression ranges described below satisfy all, but it is not always necessary to satisfy all of them, and it is possible to achieve a predetermined operation and effect by satisfying the respective defined ranges. .
[0030]
0.01 <| φd / φg | <0.4 (1)
However,
φd: power of diffractive optical surface,
φg: power of the refractive optical surface of the lens element provided with the diffractive optical surface,
It is.
[0031]
The conditional expression range (1) defines the ratio between the power of the diffractive optical surface and the power of the refractive optical surface of the lens element provided with the diffractive optical surface. When the value exceeds the upper limit of the conditional expression range (1), the power on the diffractive optical surface becomes too strong, and the axial chromatic aberration is excessively corrected, which is not desirable. Conversely, if the value exceeds the lower limit of the conditional expression range (1), the power of the diffractive optical surface becomes too weak, and the color correction ability is undesirably reduced.
[0032]
0.01 <| φd / φgr | <1 (2)
However,
φd: power of diffractive optical surface,
φgr: combined power of the refractive optical surfaces of the zoom group including the diffractive optical surface (a lens group that is a block of lenses whose distance does not change during zooming)
It is.
[0033]
The conditional expression range (2) defines the ratio between the power of the diffractive optical surface and the combined power of the refractive optical surfaces of the zoom group including the diffractive optical surface. When the value exceeds the upper limit of the conditional expression range (2), the power on the diffractive optical surface in the zoom group becomes too strong, and the axial chromatic aberration is excessively corrected, which is not desirable. Conversely, if the lower limit value of the conditional expression range (2) is exceeded, the power of the diffractive optical surface becomes too weak, and the color correction capability is undesirably reduced.
[0034]
0.05 <| φd × fw × 10 | <1 (3)
However,
φd: power of diffractive optical surface,
fw: focal length in the shortest focal length state of the zoom lens system,
It is.
[0035]
The conditional expression range (3) is the product of the power of the diffractive optical surface and the focal length of the zoom lens system in the shortest focal length state (that is, the ratio of the power of the diffractive optical surface to the power of the entire system in the shortest focal length state). ). When the value exceeds the upper limit of the conditional expression range (3), the power on the diffractive optical surface in the entire system becomes too strong, and the axial chromatic aberration is excessively corrected, which is not desirable. Conversely, if the value exceeds the lower limit of the conditional expression range (3), the power of the diffractive optical surface becomes too weak, and the color correction ability is undesirably reduced.
[0036]
1 <| R2 × Hmax / λ0 | <60 (4)
However,
R2: second-order phase coefficient (1 / mm) of the diffractive optical surface,
Hmax: lens effective diameter (mm),
λ0: Design center wavelength (mm)
It is.
[0037]
The conditional expression range (4) is an expression relating to the pitch of the diffraction pattern on the diffractive optical surface provided on the lens surface. If the value exceeds the upper limit of conditional expression range (4), the pitch of the diffraction pattern becomes too small, making the production difficult, which is not desirable. Conversely, if the value exceeds the lower limit of the conditional expression range (4), the power of the diffractive optical surface becomes too weak, and the color correction ability is undesirably reduced.
[0038]
−0.8 <φGr1 × fw <−0.3 (5)
However,
φGr1: composite power of all surfaces in the first group,
fw: focal length in the shortest focal length state of the zoom lens system,
It is.
[0039]
Conditional expression range (5) defines the product of the power of the first group and the focal length in the shortest focal length state (ie, the ratio of the power of the first subgroup to the power of the entire system in the shortest focal length state). ing. When the value exceeds the upper limit of conditional expression range (5), the power of the first lens unit becomes too weak, and the size of the zoom lens system increases, so that a compact zoom lens system cannot be achieved. Conversely, if the lower limit of the conditional expression range (5) is exceeded, the power of the first lens unit becomes too strong, and it becomes difficult to correct various aberrations generated in the first lens unit, which is not desirable.
[0040]
0.2 <φGrL × fw <0.6 (6)
However,
φGrL: when the zoom lens system includes, in order from the object side, a first unit having negative power, a second unit having positive power, and at least one subsequent lens unit, Combined power of all lens groups arranged closer to the image side than the second group except the group,
fw: focal length in the shortest focal length state of the zoom lens system,
It is.
[0041]
The conditional expression range (6) is the product of the power of the image-side lens unit and the focal length in the shortest focal length state (ie, the ratio of the power of the image-side lens unit to the power of the entire system in the shortest focal length state). Stipulates. When the value exceeds the upper limit of conditional expression range (6), the power of the image-side lens unit becomes too strong, so that various aberrations generated in the image-side lens unit cannot be corrected. Conversely, if the lower limit value of the conditional expression range (6) is exceeded, the power of the image-side lens unit becomes too weak, and the pupil position exiting to the image plane is located near the image plane. This is far from the required condition of telecentric incidence on the CCD, which is undesirable.
[0042]
0.1 <LB × fw <0.5 (7)
However,
LB: lens back, the distance from the surface vertex having the power of the lens element arranged closest to the image side to the image plane,
fw: focal length in the shortest focal length state of the zoom lens system,
It is.
[0043]
The conditional expression range (7) defines the product of the focal length and the lens back in the shortest focal length state (that is, the ratio of the total system power to the lens back in the shortest focal length state). When the value exceeds the upper limit of conditional expression range (7), the lens back becomes too large, and it is difficult to achieve a compact zoom lens system. Conversely, if the lower limit of the conditional expression range (7) is exceeded, the lens back becomes too short, and dust and dust adhering to the lens surface may be captured on the solid-state imaging device, which is not desirable.
[0044]
It is desirable that the diffraction pattern on the diffractive optical surface is blazed (sawtoothed). The blazed structure can improve the diffraction efficiency. As a method of blazing, a semiconductor manufacturing technology is applied to produce a saw-tooth pattern by approximating it in a step shape (binary optics), or a die is manufactured by precision cutting, etc., and a glass or resin material is produced. Can be realized by a method of molding. As a method of molding, both a method of integrally molding the element having the diffraction surface itself with glass or resin, and a method of molding a resin layer on a base lens made of glass or the like are possible.
[0045]
【Example】
Hereinafter, the configuration and the like of the zoom lens system included in the imaging apparatus embodying the present invention will be described more specifically with reference to construction data, aberration diagrams, and the like. Examples 1 to 5 described here as examples correspond to the above-described first to fifth embodiments, respectively, and the lens configuration diagrams (FIGS. 1 to 5) representing the first to fifth embodiments are shown in FIGS. And the corresponding lens configurations of Examples 1 to 5 are shown.
[0046]
In the construction data of each embodiment, ri (i = 1, 2, 3,...) Is the radius of curvature (mm) of the i-th surface counted from the object side, and di (i = 1, 2, 3,. ...) indicate the i-th axial top surface interval (mm) counted from the object side, and Ni (i = 1, 2, 3, ...), νi (i = 1, 2, 3, ...). .) Indicate the refractive index (Nd) and Abbe number (νd) of the i-th optical element counted from the object side with respect to the d-line. In the construction data, the axial top surface interval that changes during zooming is a variable interval from the shortest focal length state (wide-angle end, W) to the intermediate focal length state (middle, M) to the longest focal length state (telephoto end, T). Shows the value of The focal length (f, mm) and F number (FNO) of the entire system corresponding to each focal length state (W), (M), (T) are shown together with other data.
[0047]
The surface with * added to the radius of curvature ri indicates a surface constituted by an aspheric surface, and is defined by the following expression (AS) representing the surface shape of the aspheric surface. The aspherical surface data of each example is shown together with other data.
[0048]
Z (h) = r- (r ＾ 2-εh ＾ 2) ＾ 1/2 + (A4 ・ H ＾ 4 + A6 ・ H ＾ 6 + A8 ・ H ＾ 8 +＋) (AS)
However,
r: radius of paraxial curvature of aspheric surface
h: distance in a direction perpendicular to the optical axis;
ε: elliptic coefficient,
Ai: the i-th order aspherical surface coefficient of the aspherical surface,
It is.
[0049]
A surface in which the curvature radius ri is marked with # indicates a diffractive optical surface, and is defined by the following equation (DE) representing a phase shape that determines the shape of the diffraction pattern. The diffractive optical surface data of each example is shown together with other data.
[0050]
φ (h) = 2π (R2 · h ＾ 2 + R4 · h ＾ 4 + R6 · h ＾ 6 + ··) / λ0 (DE)
However,
h: distance in a direction perpendicular to the optical axis;
Ri: the i-th phase coefficient,
λ0: design center wavelength,
It is.

Tables 1 and 2 below show numerical values of the respective examples with respect to the conditional expressions.
[0051]
[Table 1]

[0052]
[Table 2]

[0053]
6 to 10 are aberration diagrams of the first to fifth embodiments, and show aberrations of the zoom lens systems of the respective embodiments in an infinity in-focus state. 5 to 10, various aberrations in the shortest focal length state, the intermediate focal length state, and the longest focal length state are shown in order from the top. The aberration diagrams at each focal length state show, in order from the left, spherical aberration, astigmatism, and distortion. In the spherical aberration diagram, the vertical axis represents a value H / H0 obtained by normalizing the entrance height H to the entrance pupil by its maximum height H0 (= 1) (ie, a relative height that cuts the entrance pupil plane), and the horizontal axis represents Denotes a shift amount (mm) in the optical axis direction from the paraxial imaging position. The solid line represents the amount of spherical aberration with respect to the d-line (wavelength: λd = 587.6 nm). In the astigmatism diagram, the vertical axis represents the image height Y ′ (mm), and the horizontal axis represents the amount of deviation (mm) in the optical axis direction from the paraxial imaging position. The solid line X represents astigmatism on the sagittal surface, and the solid line Y represents astigmatism on the meridional surface. In the distortion diagram, the vertical axis represents the image height Y ′ (mm), and the horizontal axis represents the distortion amount (%).
[0054]
【The invention's effect】
As described above, according to the zoom lens system of each embodiment, it is possible to provide a compact imaging device with little residual chromatic aberration, while having a high-performance and high-magnification zoom lens system.
[Brief description of the drawings]
FIG. 1 is a lens configuration diagram of a first embodiment (Example 1).
FIG. 2 is a lens configuration diagram of a second embodiment (Example 2).
FIG. 3 is a lens configuration diagram of a third embodiment (Example 3).
FIG. 4 is a lens configuration diagram of a fourth embodiment (Example 4).
FIG. 5 is a lens configuration diagram of a fifth embodiment (Example 5).
FIG. 6 is an aberration diagram of Example 1 in a state of focusing on infinity.
FIG. 7 is an aberration diagram of Example 2 in a state of focusing on infinity.
FIG. 8 is an aberration diagram for Example 3 in a state of focusing on infinity.
FIG. 9 is an aberration diagram for Example 4 in a state of focusing on infinity.
FIG. 10 is an aberration diagram for Example 5 in a state of focusing on infinity.
FIG. 11 is a configuration diagram showing an outline of the present invention.
[Explanation of symbols]
LPF: parallel plane plate SR corresponding to an optical low-pass filter SR: solid-state imaging device TL: zoom lens system Gr1: first lens group Gr1
Gr2: second lens group Gr2
Gr3: third lens group Gr3
ST: Aperture

Claims (5)

A zoom lens system having a plurality of lens groups, wherein the distance between the plurality of lens groups is changed so that an optical image of an object can be continuously and optically zoomable, and an optical system formed by the zoom lens system An imaging device including an imaging element that converts an image into an electric signal,
The zoom lens system, in order from the object side,
A first group having negative power;
A second group having a positive power and arranged at a variable interval on the image side of the first group;
At least one diffractive optical surface in the zoom lens system, comprising: an image side group including at least one lens group including a third group disposed at a variable interval on the image side of the second group. An imaging device comprising: The imaging apparatus according to claim 1, wherein the following conditional expression range (1) is satisfied:
0.01 <| φd / φg | <0.4 (1)
However,
φd: power of diffractive optical surface,
φg: power of the refractive optical surface of the lens element provided with the diffractive optical surface,
It is. The imaging apparatus according to claim 1, wherein the following conditional expression range (2) is satisfied:
0.01 <| φd / φgr | <1 (2)
However,
φd: power of diffractive optical surface,
φgr: combined power of the refractive optical surfaces of the zoom group including the diffractive optical surface (a lens group that is a block of lenses whose distance does not change during zooming)
It is. The imaging apparatus according to claim 1, wherein the following conditional expression range (3) is satisfied:
0.05 <| φd × fw × 10 | <1 (3)
However,
φd: power of diffractive optical surface,
fw: focal length in the shortest focal length state of the zoom lens system,
It is. The imaging apparatus according to claim 1, wherein the following conditional expression range (4) is satisfied:
1 <| R2 × Hmax / λ0 | <60 (4)
However,
R2: second-order phase coefficient (1 / mm) of the diffractive optical surface,
Hmax: lens effective diameter (mm),
λ0: Design center wavelength (mm)
It is.

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