JP2012181436A - Zoom lens, camera, and information device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement a zoom lens which has a compact focusing group for focusing, has the focusing group displaced by a small amount in accordance with focusing, has high-speed AF, is small-sized, has high performance and a wide angle of view, and is suitable for a digital still camera.SOLUTION: The zoom lens includes, in order from the object side, a first lens group I having a positive refracting power, a second lens group II having a negative refracting power, a third lens group III having a negative refracting power, a fourth lens group IV having a positive refracting power, and a fifth lens group V having a positive refracting power. A stop S is disposed between the third lens group and the fourth lens group. In zooming from a wide angle end and to a telephoto end, each lens group is independently moved toward the object side. The third lens group comprises one negative lens. Focusing from an infinity object to a close object is performed by moving the third lens group in the optical axis direction. A focal length f2 of the second lens group and a focal length ft of an entire system at the telephoto end satisfy formula 0.7<|f2/ft|<2.4.

Description

  The present invention relates to a zoom lens, a camera, and an information device.

  In recent years, a zoom lens is generally used as a photographing optical system used for a digital still camera or the like, and in particular, a zoom lens including a “angle of view of about 50 mm in terms of 35 mm size” in a focal length range has been generalized. In addition, there is a strong demand for “high speed autofocus (hereinafter abbreviated as“ AF ”)” along with downsizing and widening of the angle.

  A so-called “positive lead type” zoom lens having a leading zoom group is known as a configuration capable of achieving both a large zoom ratio and a reduction in the overall length.

  This positive lead type zoom lens is a type that performs focusing by displacing the lens group inside the lens, and distributes positive, negative, and negative refractive power in order from the object side to the object side of the aperture. Patent Documents 1 to 4 are known in which the first to third lens groups are arranged and focusing is performed by moving the third lens group.

  In particular, in the zoom lens described in Patent Document 4, the third lens group for performing focusing is composed of “one negative lens”, thereby reducing the weight of the third lens group and increasing the focusing speed. Yes.

  However, the zoom lens described in Patent Document 4 requires a large amount of displacement required for focusing, and there is still room for improvement in realizing “downsizing in use” of the zoom lens.

  In view of the above-described circumstances, the present invention is a zoom lens suitable for a digital still camera with a compact focus group for performing focusing, a small amount of displacement of the focus group accompanying focusing, high-speed AF, small size, high performance, and wide angle of view. It is an issue to make this possible.

  The present invention also has a resolving power corresponding to an image sensor exceeding 5 million to 10 million pixels with a half angle of view at the wide angle end of 37.5 degrees or more and a zoom ratio of about 1.9 to 2.9 times. The realization of a high-speed AF and a compact, high-performance zoom lens is an issue.

  Another object of the present invention is to realize a camera and an imaging apparatus using such a zoom lens.

The zoom lens according to claim 1, in order from an object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a positive refractive power. A fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and a stop disposed between the third lens group and the fourth lens group, and zooming from the wide-angle end to the telephoto end. At this time, each lens group independently moves to the object side.
The third lens group is composed of a single negative lens, and focusing from an object at infinity to a near object is performed by moving the third lens group in the optical axis direction.

The focal length of the second lens group is f2, and the focal length of the entire system at the telephoto end is ft.
(1) 0.7 <| f2 / ft | <2.4
Satisfied.

In the zoom lens according to claim 1, the optical total length at the telephoto end: Lt, and the thickness on the optical axis of one negative lens constituting the third lens group: D3 are:
(2) 80 <Lt / D3 <120
Is preferably satisfied (claim 2).

  In the zoom lens according to claim 1 or 2, the lens closest to the image side in the fifth lens group is preferably a “negative lens having at least one aspherical shape” (claim 3).

  The zoom lens according to any one of claims 1 to 3 can be used in an “information device that reads an image from a zoom lens with an imaging device”. In this case, “the distortion aberration is allowed within a range that can be corrected by electronic processing of data that has been computerized by the image sensor” (claim 4).

The camera according to the present invention includes the zoom lens according to any one of claims 1 to 4 as a photographing optical system (claim 5).
The camera can be configured as a “camera having a function of reading an image from a zoom lens with an imaging device”. In this case, the zoom lens according to any one of claims 1 to 3 may be used. Further, the one described in claim 4 can also be used.

  That is, the camera can be implemented as a digital still camera, a video camera, a silver salt camera, or the like, but can be implemented as a “camera having a function of reading an image by a zoom lens with an imaging device” like a digital still camera. In such a case, the zoom lens according to claim 4 is suitable (claim 6).

  An information device according to the present invention includes the zoom lens according to any one of claims 1 to 4 as a photographing optical system of a camera function unit, and is configured as a portable information terminal device. Item 7).

  Condition (1) is a right to “balance the negative refractive power of the second lens group to the positive refractive power of the entire system”. The second lens group is responsible for the main zoom function, and if the upper limit of condition (1) is exceeded, the negative refractive power of the second lens group becomes too weak, and a given zoom ratio is achieved. However, it is necessary to greatly displace the second lens group, which increases the overall length of the lens, which is disadvantageous for downsizing the zoom lens, and hence the camera and portable information terminal device using the zoom lens.

  When the lower limit of the condition (1) is exceeded, the negative refractive power of the second lens group becomes too strong, the back focus of the zoom lens becomes long, which is disadvantageous for miniaturization of the camera and the portable information terminal device.

  The zoom lens according to claim 1 has the above-described configuration, and the third lens group that performs focusing is formed of “one negative lens”. However, if the above condition (1) is satisfied, the zoom lens and the camera / portable information terminal device using the zoom lens can be made compact.

  Condition (2) is an advantageous condition for making the zoom lens / camera / personal digital assistant compact and increasing the focusing speed. The thickness on the optical axis of the third lens group: D3 is the total length at the telephoto end: By satisfying the condition (2) for Lt, it is possible to reduce the size and speed of focusing.

  If the lower limit of the condition (2) is exceeded, the “thickness of the third lens group is large” with respect to the total length at the telephoto end, which is disadvantageous for miniaturization of the zoom lens, and the third lens for performing high-speed focusing. The energy for driving the group tends to increase, and if the driving energy is suppressed, the moving speed for focusing becomes slow, and high-speed autofocus becomes difficult.

  If the upper limit of condition (2) is exceeded, the entire lens length becomes long, or the thickness of the third lens group (one negative lens) becomes thin, making it difficult to process the lens of the third lens group.

  In the zoom lens according to the third aspect, as described above, the lens closest to the image side of the fifth lens group is “a negative lens having at least one aspherical surface”. However, the fifth lens group has a negative refractive power. By disposing the lens having the negative refractive power that the second lens group and the third lens group should have part of the negative lens in the fifth lens group, the distribution of the negative refractive power is It can be dispersed to the second, third, and fifth lens groups, which is advantageous for aberration correction.

  Further, by making “at least one surface” of the negative lens an aspherical shape, the effect of aberration correction can be further enhanced. In other words, the fifth lens group is arranged closest to the image side in all the lens groups, and the negative lens is arranged by arranging an aspherical surface in the “negative lens closest to the image plane” in the fifth lens group. It is possible to comprehensively correct aberrations occurring on the object side.

When the image formed by the lens is imaged on the imaging surface of the “imaging device” and the image is converted to information by the imaging device, the imaged image is processed electronically, and the image is formed. It is known that distortion aberration can be corrected.
Accordingly, on the premise of such distortion aberration correction, if “distortion aberration within a range that can be corrected by electronic processing” is allowed as in the zoom lens of claim 4, aberrations other than distortion aberration can be “correctly corrected”. Can contribute to wide angle of view, high zoom ratio, and high performance.

  Since distortion is more likely to occur as the angle of view becomes larger, it is preferable that the distortion can be corrected at least at the wide-angle end, preferably in the zooming region including the wide-angle end and the intermediate focal length. Distortion correction by electronic processing is possible up to about 20% distortion.

  In addition, it is preferable that the first lens group has a “configuration including one negative lens and one positive lens” in order from the object side. More specifically, in order from the object side, a negative meniscus lens having a convex surface facing the object side and a positive lens having a strong convex surface facing the object side are preferably used.

In order to increase the zoom ratio, in particular, to increase the focal length at the telephoto end, it is necessary to increase the “combining magnification of the second to fifth lens groups” at the telephoto end. The aberration generated in the above is magnified on the image plane.
For this reason, in order to advance the zooming ratio, it is necessary to sufficiently reduce the amount of aberration generated in the first lens group. For this purpose, the first lens group is preferably configured as described above.

  The second lens group is preferably composed of three lenses in order from the object side: a negative lens having a large curvature surface facing the image side, a negative lens, and a positive lens.

  By “arrangement of negative lens, negative lens, and positive lens” in order from the object side, it becomes possible to “close the principal point of the second lens group to the image side” and contribute to shortening the total length of the optical system at the telephoto end. .

  Although it may be simpler in terms of the mechanism that the aperture diameter of the aperture is “constant regardless of zooming”, the change in the F number is reduced by increasing the aperture diameter at the telephoto end compared to the wide-angle end. You can also. If it is necessary to reduce the amount of light that reaches the image plane, the aperture may be made smaller. However, reducing the amount of light by inserting an ND filter or the like without greatly changing the aperture diameter reduces the resolving power due to the diffraction phenomenon. Is preferable.

As described above, according to the present invention, a novel zoom lens can be realized.
In the zoom lens according to the present invention, as described above, the third lens that performs focusing is composed of “one negative lens” and is light in weight, so that the driving energy during focusing can be reduced, so that high-speed AF is possible. It is possible to reduce the size of the zoom lens.

  As shown in the examples described later, the half angle of view at the wide-angle end is 37.5 degrees or more, and the zoom ratio is about 1.9 to 2.9 times. A zoom lens having a resolving power corresponding to the image sensor can be realized.

  Further, as described in the first to fifth embodiments described later, by “allowing distortion within a range that can be corrected by electronic processing” as in claim 4, “very good correction of aberrations other than distortion” will be described. Is possible.

  By having such a compact and high-performance zoom lens as an imaging optical system, a compact and high-performance camera and information device can be realized.

FIG. 4 is a diagram for explaining a lens configuration of a zoom lens of Example 1 and displacements of each lens unit at the time of zooming. FIG. 6 is a diagram for explaining a lens configuration of a zoom lens according to Embodiment 2 and displacement of each lens unit upon zooming. FIG. 6 is a diagram for explaining a lens configuration of a zoom lens according to Example 3 and displacements of each lens unit upon zooming. FIG. 10 is a diagram for explaining a lens configuration of a zoom lens of Example 4 and displacements of each lens unit upon zooming. FIG. 10 is a diagram for explaining a lens configuration of a zoom lens of Example 5 and displacement of each lens unit at the time of zooming. FIG. 3 is an aberration diagram at a wide angle end of the zoom lens according to Example 1; FIG. 4 is an aberration diagram for the zoom lens of Example 1 at an intermediate focal length. FIG. 4 is an aberration diagram at a telephoto end of the zoom lens in Example 1; FIG. 6 is an aberration diagram at a wide-angle end of the zoom lens according to Example 2; 6 is an aberration diagram at an intermediate focal length of the zoom lens of Example 2. FIG. 6 is an aberration diagram at a telephoto end of a zoom lens in Example 2. FIG. FIG. 10 is an aberration diagram at a wide-angle end of the zoom lens according to Example 3; FIG. 10 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 3; 6 is an aberration diagram at a telephoto end of a zoom lens in Example 3; FIG. FIG. 10 is an aberration diagram at a wide-angle end of the zoom lens according to Example 4; FIG. 10 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is an aberration diagram at a telephoto end of a zoom lens in Example 4; FIG. 10 is an aberration diagram at a wide-angle end of the zoom lens according to Example 5; FIG. 10 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 5; 10 is an aberration diagram at a telephoto end of a zoom lens in Example 5. FIG. It is a figure for demonstrating one Embodiment of a portable information terminal device. It is a figure for demonstrating the system of the apparatus of FIG. It is a figure for demonstrating the electronic correction | amendment of a distortion aberration.

Hereinafter, embodiments will be described.
1 to 5 show an embodiment of a zoom lens. The zoom lenses shown in FIGS. 1 to 5 relate to Examples 1 to 5 described later in this order.

In order to avoid complications, the codes are shared in FIGS.
The symbol “I” designates the first lens group, the symbol “II” designates the second lens group, the symbol “III” designates the third lens group, the symbol “IV” designates the fourth lens group, and the symbol “V” designates the fifth lens group. Show. Further, an aperture stop is indicated by a symbol “S”. The left side of the figure is the “object side” and the right side is the “image side”.
Reference numeral F denotes a “transparent parallel plate”. The transparent parallel flat plate F is used for various filters such as optical low-pass filters and infrared cut filters (transparent parallel flat plate on the object side) and cover glass for image sensors such as CCD sensors (transparent parallel flat plate on the seal glass image side). It is shown as “equivalent two transparent parallel plates”.

  1 to 5 show “lens group arrangement at the wide-angle end”, the middle figure shows “lens group arrangement at the intermediate focal length”, and the lowermost figure shows “lens group arrangement at the telephoto end”. FIG. When zooming from the wide-angle end to the telephoto end, each lens group of the zoom lens moves as indicated by an arrow from the uppermost state to the lowermost state in the figure.

  As described above, the zoom lens shown in FIGS. 1 to 5 includes, in order from the object side to the image side along the optical axis, the first lens group I having a positive refractive power and the second lens group having a negative refractive power. II, a third lens group III having a negative refractive power, a fourth lens group IV having a positive refractive power, and a fifth lens group V having a positive refractive power are arranged, and the third lens group III and the fourth lens group IV The first lens unit I to the fifth lens unit V “monotonously move toward the object side independently of each other” upon zooming from the wide-angle end to the telephoto end.

  The third lens group III includes “one negative lens”, and focusing is performed by the displacement. The aperture stop S is displaced integrally with the fourth lens group IV.

  As shown in Examples 1 to 5 described later corresponding to these embodiments, each zoom lens satisfies the conditions (1) and (2).

With reference to FIGS. 21 and 22, an embodiment of a “portable information terminal device” as an imaging device will be described.
As shown in FIG. 22, the system configuration of the portable information terminal device includes a photographing lens 1 that is a “zoom lens” and a light receiving element 13 that is an “imaging device”. The image is read by the light receiving element 13, and the output from the light receiving element 13 is processed by the signal processing device 14 under the control of the central processing unit 11 and converted into digital information.

  The image converted into digital information is displayed on the liquid crystal monitor 7 and stored in the semiconductor memory 15 or used for communication to the outside by the communication card 16. The portion excluding this communication function constitutes a “camera”.

  As the photographing lens 1, the zoom lens according to any one of claims 1 to 4, specifically, a zoom lens of Examples 1 to 5 described later is used.

  The “monitored image” can be displayed on the liquid crystal monitor 7 or an image recorded in the semiconductor memory 15 can be displayed.

When the portable information terminal device is carried, the photographing lens 1 is in the “collapsed state” as shown in FIG. 21A. When the power is turned on by operating the power switch 6, the lens barrel is extended from the housing 5. In the state where the lens barrel is extended, each group of zoom lenses in the lens barrel is “for example, an arrangement at the wide-angle end”, and the arrangement of each group is changed by operating a zoom lever (not shown), and the telephoto end Can be scaled to
At this time, the viewfinder 2 also zooms in conjunction with the change in the angle of view of the taking lens 1.

  Focusing is performed by “half-pressing” the shutter button 4.

  Focusing is performed by moving the third lens group, but can also be performed by “moving the light receiving element”. When the shutter button 4 is further pressed, shooting is performed, and thereafter the above processing is performed.

  When the image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside using the communication card 16 or the like, the operation button 8 is operated. The semiconductor memory 15 and the communication card 16 are inserted into dedicated or general-purpose slots 9 for use.

  When the photographic lens is in the “collapsed state”, the lens groups of the zoom lens do not necessarily have to be arranged on the optical axis. For example, if the second lens group is retracted from the optical axis to be “stored in parallel with other lens groups”, the portable information terminal device can be further reduced in thickness.

Hereinafter, five specific examples will be given.
The meanings of the symbols in the examples are as follows.

f: Focal length of the entire system
F: F number
ω: Half angle of view
r: radius of curvature (paraxial radius of curvature for aspheric surfaces)
D: Surface spacing
Nd: Refractive index
νd: Abbe number
K: Aspherical conical constant
A4: Fourth-order aspheric constant
A6: 6th-order aspheric constant
A8: 8th-order aspheric constant
A10: 10th-order aspheric constant
A12: 12th-order aspheric constant
A14: 14th-order aspheric constant
“Aspherical shape” means the reciprocal of the paraxial radius of curvature (paraxial curvature): C, height from the optical axis: H, conic constant: K, and the aspheric coefficient of each of the above orders, where X is the optical axis direction. As an aspheric quantity in, the well-known formula:
^{X = CH 2 / [1 +} √ {1- (1 + K) C 2 H 2}] + A4 · H 4 + A6 · H 6
+ A8 · H ⁸ + A10 · H ¹⁰ + A12 · H ¹² + A14 · H ¹⁴
The shape is specified by giving a paraxial radius of curvature: R (= 1 / C), a conic constant: K, and an aspheric coefficient: A4 to A14.
The unit of “amount having a dimension of length” is “mm”.

  In each example, “HOYA” in “Glass type” is “HOYA Corporation”, and (OHARA) is “Ohara Corporation”, and names of optical glass types of these manufacturing companies are listed.

"Example 1"
The zoom lens according to the first embodiment has been described with reference to FIG.
The first lens unit I includes a negative meniscus lens having a convex surface directed toward the object side and a cemented lens of a positive meniscus lens having a convex surface directed toward the object side.

  The second lens group II includes a negative meniscus lens having a convex surface on the object side and an aspheric surface on the object side, a biconcave lens having a strong concave surface on the image side, and a biconvex lens having a strong convex surface on the object side. .

  The third lens group III is a single biconcave lens having a stronger concave surface on the object side.

  The fourth lens group IV includes a biconvex lens having a stronger convex surface on the object side and an aspheric object side surface, a biconvex lens having a stronger convex surface on the object side, and a negative meniscus lens having a convex surface on the object side. .

  The fifth lens group V includes a biconvex lens having a stronger convex surface on the object side and a negative meniscus lens having a convex surface on the image side and both surfaces being aspherical.

  Each lens group moves as shown in FIG. 1 when zooming from the wide-angle end to the telephoto end. Although each lens group moves monotonously toward the object side, the distance between the first lens group I and the second lens group II increases, and the distance between the second lens group II and the third lens group III also increases. The distance between the third lens group III and the fourth lens group IV decreases, and the distance between the fourth lens group IV and the fifth lens group V decreases. The aperture stop S moves integrally with the fourth lens group IV.

f = 15.99 to 46.53 F = 3.66 to 5.81 ω = 41.8 to 17.08
The data of Example 1 is shown in Table 1.

"Aspherical surface"
An aspherical surface is a surface marked with “*” in Table 1 above. The same applies to the following embodiments.

  The data of the aspherical surface of Example 1 is shown below.

4th page
K = 0
A4 = 1.056440E-06
A6 = 4.970200E-08
A8 = -7.07385E-10
A10 = 5.361300E-12
A12 = -1.57191E-14
Side 13
K = 0
A4 = -7.78796E-05
A6 = -2.65621E-07
A8 = -1.50697E-09
21st page
K = 0
A4 = 3.625180E-05
A6 = 1.430340E-06
A8 = -1.49906E-08
22nd page
K = 0
A4 = 1.042670E-04
A6 = 1.381650E-06
A8 = -1.17092E-08
In the above aspherical notation, for example, “-1.17092E-08” means “-1.17092 × 10 ⁻⁸ ”. The same applies to the following.

"Variable amount"
Variable amounts of data are shown in Table 2.

  6, 7, and 8 sequentially show aberration diagrams of the first embodiment at the wide-angle end, the intermediate focal length, and the telephoto end. The broken line in the spherical aberration diagram represents “sine condition”, the solid line in the astigmatism diagram represents “sagittal”, and the broken line represents “meridional”. Further, “g” and “d” represent the g line and the d line, respectively. The same applies to other aberration diagrams.

"Example 2"
The zoom lens of Example 2 has been described with reference to FIG.

  The second lens of the second lens group II is a “biconcave lens with a stronger concave surface facing the image side”, the third lens of the fourth lens group IV is a “biconcave lens with a stronger concave surface facing the image side”, and the others The same as in the first embodiment.

f = 18.65-54.3 F = 3.62-5.83 ω = 37.5-14.8
The data of Example 2 is shown in Table 3.

"Aspherical surface"
The data of the aspherical surface of Example 2 is shown below.

4th page
K = 0
A4 = -2.56108E-06
A6 = 1.044020E-07
A8 = -1.4309E-09
A10 = 1.355110E-11
A12 = -5.04361E-14
Side 13
K = 0
A4 = -9.25137E-05
A6 = -3.51547E-07
A8 = -8.00052E-09
21st page
K = 0
A4 = -2.51375E-04
A6 = 3.572660E-06
A8 = 1.359970E-08
22nd page
K = 0
A4 = -1.75754E-04
A6 = 4.150840E-06
A8 = -1.1655E-08.

"Variable amount"
Variable amounts of data are shown in Table 4.

  FIG. 9, FIG. 10, and FIG. 11 show aberration diagrams in Example 2 at the wide-angle end, the intermediate focal length, and the telephoto end, respectively.

"Example 3"
The zoom lens according to the third embodiment has been described with reference to FIG.

  Example 2 is the same as Example 1 except that the second lens of the second lens group II is a “negative meniscus lens having a convex surface facing the image side”.

f = 16.15 to 38 F = 3.63 to 5.86 ω = 41.5 to 20.6
The data of Example 3 is shown in Table 5.

"Aspherical surface"
The data of the aspherical surface of Example 3 is shown below.

4th page
K = 0
A4 = 2.777450E-05
A6 = -3.99444E-08
A8 = 6.048460E-10
A10 = 1.095400E-12
A12 = -2.48491E-14
Side 13
K = 0
A4 = -9.36505E-05
A6 = 4.158310E-08
A8 = -5.89151E-09
21st page
K = 0
A4 = 5.741240E-06
A6 = -1.82504E-06
A8 = 4.009180E-09
22nd page
K = 0
A4 = 1.736520E-04
A6 = -1.06638E-06
A8 = 2.185120E-08.

"Variable amount"
The variable amount of data is shown in Table 6.

  FIG. 12, FIG. 13, and FIG. 14 show aberration diagrams of Example 3 at the wide-angle end, the intermediate focal length, and the telephoto end, respectively.

Example 4
The zoom lens of Example 4 is the one shown in FIG.

  The second lens of the first lens group I is “a biconvex lens having a stronger convex surface on the object side” and the second lens of the fifth lens group is “a biconvex lens having an aspheric surface only on the image side”. The same as in the first embodiment.

f = 16.15 to 31.66 F = 3.62 to 5.84 ω = 41.5 to 24.3
The data of Example 4 is shown in Table 7.

"Aspherical surface"
The aspherical data of Example 4 is shown below.

4th page
K = 0
A4 = 5.736250E-06
A6 = 1.541920E-07
A8 = -1.54552E-09
A10 = 2.609640E-11
A12 = -1.36118E-13
Side 13
K = 0
A4 = -6.60531E-05
A6 = -9.67387E-08
A8 = -6.97485E-09
22nd page
K = 0
A4 = 2.216200E-04
A6 = 2.466620E-06
A8 = -2.45507E-08
A10 = 6.485260E-10.

"Variable amount"
Variable amounts of data are shown in Table 8.

  FIG. 15, FIG. 16, and FIG. 17 show aberration diagrams in Example 4 at the wide-angle end, intermediate focal length, and telephoto end, respectively.

"Example 5"
The zoom lens of Example 5 is the one shown in FIG.

  The lens configuration is the same as in Example 1.

f = 15.99 to 46.56 F = 3.65 to 5.85 ω = 41.8 to 17.07
The data of Example 5 is shown in Table 9.

"Aspherical surface"
The aspheric data of Example 5 is shown below.

4th page
K = 0
A4 = 3.219740E-06
A6 = 3.603850E-08
A8 = -5.10179E-10
A10 = 3.418800E-12
A12 = -8.46642E-15
Side 13
K = 0
A4 = -7.30888E-05
A6 = -2.79226E-07
A8 = -1.37626E-09
21st page
K = 0
A4 = 2.979630E-05
A6 = 1.179710E-06
A8 = -6.349E-09
22nd page
K = 0
A4 = 9.580120E-05
A6 = 1.208010E-06
A8 = -8.5897E-09.

"Variable amount"
Variable amounts of data are shown in Table 10.

  FIG. 18, FIG. 19, and FIG. 20 show aberration diagrams in Example 5 at the wide-angle end, the intermediate focal length, and the telephoto end, respectively.

"Parameter values for conditional expressions"
Table 11 shows the parameter values of the conditional expressions in Examples 1 to 5.

  In each example, the parameters of the conditions (1) and (2) are within the range.

  As described above, the lens configuration of each lens group is such that the first lens group I is a “two negative / positive two lens configuration”, the second lens group is a “three negative / negative / positive” lens configuration, and the third lens group III. Is a negative lens, the fourth group is “a positive / positive / negative three-lens configuration”, and the fifth group is a “positive / negative two-lens configuration”. Such a lens configuration is preferable.

  In each of the zoom lenses of Examples 1 to 5, the light beam that passes through the first lens group I at the wide-angle end is obtained by moving the first lens group I toward the object side during zooming from the wide-angle end to the telephoto end. The height is reduced to suppress an increase in size of the first lens unit I due to a wide angle.

  Each of the zoom lenses according to the first to fifth embodiments allows “electronically correctable distortion” at the wide-angle end, and electronically corrects these distortions. That is, at the wide angle end, the paraxial image height is set to 13 mm, and the corrected image height is electronically corrected to 14.3 mm.

  Various electronic corrections of distortion can be considered, and an example will be described with reference to FIG.

  In FIG. 23, reference numeral Im <b> 1 indicates “the shape of the light receiving surface of the image sensor”, which has a rectangular shape. A circle IC1 circumscribing the light receiving surface shape Im1 is an image circle that covers the light receiving surface shape Im1, and is an “imaging range” at the telephoto end / intermediate focal length.

  In FIG. 23, reference numeral 1m2 indicates the “image plane shape near the wide-angle end” in an explanatory manner. In the vicinity of the wide-angle end, negative distortion is intentionally allowed, so the image plane shape Im2 is a “barrel shape”. Note that the negative distortion in FIG. 23 is depicted as “slightly exaggerated”.

  Such “barrel-shaped distortion” is electronically corrected to a shape that matches the light-receiving surface shape Im1.

  Consider a “pixel” on a straight line that forms an angle θ with respect to a vertical reference line from the center of the light-receiving surface shape Im1 as shown in FIG.

As shown in the figure, when the distance from the center of the light receiving element corresponding to this pixel is “X”, and the distortion from the center: X is Dis (X) [%], the distance is “X”. What is necessary is just to correct | amend a certain pixel to the position of "100X / (100 + Dis (X))" in said "on the straight line". In this way, it is possible to capture an image in which “distortion aberration at the wide-angle end” is corrected favorably.
By this electronic correction, the ideal image height at the intermediate focal length and the wide-angle end is set to 14.3 mm which is “the desired image circle size”. That is, the “image circle size” at the intermediate focal length / wide-angle end can be set to “(100 + Dis (X)) / 100 times” the desired image circle size.

  Since distortion can be electronically corrected as described above, if distortion is allowed to occur within the range where electronic correction is possible, the degree of freedom in correcting other aberrations and the zoom ratio can be corrected. Conditions are relaxed, and a large zoom ratio can be realized. In addition, as described above, the image circle at the intermediate focal length and the wide angle end can be made small, which has a great effect on widening the angle.

I First lens group
II Second lens group
III Third lens group
S Aperture stop
IV Fourth lens group
V 5th lens group

Japanese Patent No. 3716418 Japanese Patent No. 3397686 Japanese Patent No. 4401451 JP 2009-251112 A

Claims (7)

In order from the object, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a positive A fifth lens group having refractive power is arranged, and a diaphragm is arranged between the third lens group and the fourth lens group, and each lens group is independent when zooming from the wide angle end to the telephoto end. Moving to the object side, the third lens group is composed of one negative lens, and focusing from an infinite object to a close object is performed by moving the third lens group in the optical axis direction,
The focal length of the second lens group is f2, and the focal length of the entire system at the telephoto end is ft.
(1) 0.7 <| f2 / ft | <2.4
A zoom lens characterized by satisfying The zoom lens according to claim 1.
Optical total length at the telephoto end: Lt, Thickness on the optical axis of one negative lens forming the third lens group: D3 is a condition:
(2) 80 <Lt / D3 <120
A zoom lens characterized by satisfying The zoom lens according to claim 1 or 2,
The zoom lens according to claim 5, wherein the lens closest to the image side of the fifth lens group is a negative lens having at least one aspherical shape. The zoom lens according to any one of claims 1 to 3,
Used in an information device that reads an image from a zoom lens with an image sensor,
A zoom lens characterized in that the distortion is allowed in a range that can be corrected by electronic processing of data that is computerized by the imaging device.   5. A camera having the zoom lens according to claim 1 as an optical system for photographing.   5. A camera having a function of reading an image from a zoom lens by an imaging device, and using the zoom lens according to claim 4.   An information apparatus comprising the zoom lens according to any one of claims 1 to 5 as a photographing optical system of a camera function unit and configured as a portable information terminal device.

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