JP2007065513A - Variable magnification photographic optical system, imaging device, and personal digital assistant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a focal length on the outside of a normal zoom range from wide angle to telephoto by replacing at least one group out of lens groups constituting a variable magnification photographic optical system, with another lens group. <P>SOLUTION: The variable magnification photographic optical system includes a first group 1 having a positive focal length, a second group 2 having a negative focal length, a third group 3 having a positive focal length, and a fourth group 4 having a positive focal length in order from the object side, At least the third group 3 moves on an optical axis when a magnification is varied from a short focus end to a long focus end, and a focal length of one point can be obtained on the outside of the variable magnification range from the short focus end to the long focus end by replacing the third group 3 with a 3'-th group 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a variable magnification that can obtain a focal length other than the normal zoom range from wide angle to telephoto by replacing at least one of the lens groups constituting the variable magnification photographing optical system with another lens group. The present invention relates to an imaging optical system, an imaging device including the variable magnification imaging optical system, and a portable information terminal device.

In recent years, digital cameras equipped with a variable focus device such as a zoom lens barrel that can selectively switch between a wide-angle state when the focal length of the photographing lens is the shortest and a telephoto state when the focal length is the longest have become widespread. ing.
There is a wide variety of user needs for digital cameras equipped with this type of variable focus device, and above all, the need for higher image quality and smaller size is extremely high. Therefore, a zoom lens used as a photographing lens is also required to have both high performance and downsizing.
Here, in terms of miniaturization, first, it is necessary to shorten the entire lens length (the distance from the lens surface closest to the object side to the image plane). Furthermore, in terms of high performance, it is necessary to have a resolving power corresponding to an image sensor with at least 3 million to 5 million pixels over the entire zoom range.
In addition, there are many users who desire a wide angle of view of the taking lens, and it is desirable that the half angle of view of the zoom lens on the wide angle end side is 42 degrees or more. A half angle of view of 42 degrees corresponds to a focal length in terms of a 35 mm silver salt camera (so-called Leica version) of 24 mm.
Conventionally, zoom lenses in this field that have been reduced in size for consumer use, such as those disclosed in Patent Document 1 and those disclosed in Patent Document 2, in order from the object side to the image surface side. A first lens group having a positive refractive power and fixed at the time of zooming; a second lens group having negative refractive power and moving from the object side to the image plane side from the wide-angle end to the telephoto end at the time of zooming; Consists of a third lens unit that has refractive power and moves from the image plane side to the object side from the wide-angle end to the telephoto end during zooming, and a fourth lens unit that has positive refractive power and is fixed during zooming. Has been proposed.
Further, as in the techniques disclosed in Patent Documents 3 to 5, it is also known that the fourth lens group is movable at the time of zooming, and further advanced aberration correction is performed to further reduce the size and widen the angle. Yes.
Further, as a positive / negative / positive / positive 4 group zoom composed of one positive lens in the first group, those disclosed in Patent Documents 6 to 9 are known.
Japanese Patent No. 2920549 Patent No. 3091250 JP-A-6-94997 JP-A-10-62687 Japanese Patent Laid-Open No. 11-258507 JP 2001-042215 A JP 2001-194586 A JP 2001-242379 A JP 2001-356269 A

However, the techniques disclosed in Patent Documents 1 and 2 both have a half angle of view of less than 25 degrees, which is inadequate in terms of widening the angle.
Further, although the basic configuration of the technique of Patent Document 3 is disclosed, it does not have sufficient configuration requirements in terms of miniaturization. The technique disclosed in Patent Document 4 aims to reduce the size by reducing the number of constituent lenses, but does not perform sufficient aberration correction, and can handle an image sensor with 3 to 5 million pixels. Does not have. The technique disclosed in Patent Document 5 is relatively small, and the image performance is better than that described above, but the half angle of view is only about 33 degrees, which is insufficient in terms of widening the angle. .
Accordingly, an object of the present invention is to obtain a focal length other than the normal zoom range from wide angle to telephoto by replacing at least one of the lens groups constituting the variable magnification photographing optical system with another lens group. Is to be able to.

The invention according to claim 1 is a variable magnification photographing optical system including a variable magnification photographing optical system configured by a plurality of groups, and is a group different from the plurality of groups to be exchanged for at least one of the plurality of groups. And a focal length outside the range from the short focal end to the long focal end is obtained by the exchange.
According to a second aspect of the present invention, in the variable magnification photographing optical system according to the first aspect, the plurality of groups have a first group having a positive focal length and a first focal length having a negative focal length in order from the object side. Two groups, a third group having a positive focal length, and a fourth group having a positive focal length, and at least the third group moves on the optical axis upon zooming from the short focal end to the long focal end. It is possible to obtain a focal length of one point outside the zooming range from the short focal end to the long focal end by moving and exchanging the third group with the 3 ′ group which becomes the optical element. To do.
According to a third aspect of the present invention, in the variable magnification optical system according to the second aspect, the focal length on the telephoto side from the long focal point can be obtained from the short focal point by the exchange.
According to a fourth aspect of the present invention, in the variable magnification optical system according to the second or third aspect, the first group includes a single positive lens.
According to a fifth aspect of the present invention, in the variable magnification photographing optical system according to any one of the second to fourth aspects, 0.6 <| f2 | / f3 <0.8 (provided that fi: i th The conditional expression of the focal length (i = 1 to 3) of the lens group is satisfied.
According to a sixth aspect of the present invention, in the variable-magnification photographing optical system according to the fourth aspect, if the positive lens constituting the first group has a refractive index Nd and an Abbe number νd, Nd> 1.55, νd It is characterized by being composed of a glass material that satisfies the condition of> 55.

According to a seventh aspect of the present invention, in the variable magnification photographing optical system system according to any one of the second to sixth aspects, the most object side surface of the second group is an aspherical surface. .
According to an eighth aspect of the present invention, in the variable magnification photographing optical system according to the fourth or sixth aspect, the most object side surface of the first group is an aspherical surface.
According to a ninth aspect of the present invention, in the variable magnification optical system according to any one of the second to eighth aspects, a cemented lens is included in the third group.
According to a tenth aspect of the present invention, in the variable magnification photographing optical system according to any one of the second to ninth aspects, a surface closest to the image side of the third group is an aspherical surface. .
According to an eleventh aspect of the present invention, in the variable magnification photographing optical system according to any one of the second to tenth aspects, focusing is performed in the fourth group.
The invention according to claim 12 includes the variable magnification photographing optical system according to any one of claims 1 to 11, and the variable magnification photographing optical system includes a mechanism for performing the replacement, An imaging apparatus characterized by switching a zooming range from wide angle to telephoto and a focal length outside the zooming range by the exchange.
A thirteenth aspect of the present invention includes the variable magnification photographing optical system according to any one of the first to eleventh aspects in a camera function unit, and the variable magnification photographing optical system includes a mechanism for performing the replacement. And a portable information terminal device that switches between a zoom range from wide angle to telephoto and a focal length outside the zoom range by the exchange.

According to the first or second aspect of the present invention, it is possible to obtain a focal length outside the zooming range of the zooming optical system.
According to the third aspect of the present invention, it is possible to obtain the focal length from the short focal end to the telephoto side from the long focal end.
According to the fourth aspect of the present invention, the first group can be composed of one positive lens.
According to the fifth aspect of the present invention, the overall lens length is short, high assembly accuracy is not required, and aberration fluctuations during zooming are small.
According to the sixth aspect of the present invention, the lateral chromatic aberration at the periphery of the screen can be reduced over the entire zoom range.
According to the seventh aspect of the invention, it is possible to efficiently correct distortion, field curvature, and astigmatism on the wide angle side.
According to the eighth aspect of the invention, it is possible to effectively manipulate the light beam path.
According to the ninth aspect of the invention, it is possible to satisfactorily correct spherical aberration on the telephoto side, and at the same time, it becomes easy to correct lateral chromatic aberration. In addition, performance degradation due to eccentricity can be suppressed.
According to the tenth aspect of the present invention, the light emitted from the third group 3 that changes with zooming can be incident on the fourth group 4 at a desired angle.
According to invention of Claim 11, a focusing speed can be improved.
According to invention of Claim 12 or 13, the same effect as any one of Claims 1-11 can be show | played.

図１は、本実施形態の変倍撮影光学系の構成を示す説明図であり、図２は、同撮影光学系の各数値を示す説明図であり、図３、図４は、同撮影光学系の収差図である。
本実施形態では、変倍撮影光学系は、複数群により構成される変倍撮影光学系であり、その複数群の少なくとも１つの群を当該複数群とは別の群に交換することで、該変倍撮影光学系の短焦点端から長焦点端の範囲外の焦点距離を得ることができる。そして、本実施形態は、この変倍撮影光学系と、その複数群の少なくとも１つの群を交換するための１又は複数群を構成する光学素子とからなる変倍撮影光学系システムである。
具体的には、図１〜３の例においては、変倍撮影光学系は物体側（図１の左側）より順に、正の焦点距離を持つ第１群１と、負の焦点距離を持つ第２群２と、正の焦点距離を持つ第３群３と、正の焦点距離を持つ第４群４とを備え、短焦点端から長焦点端への変倍に際して少なくとも第３群３が光軸上を移動し（図１（ａ）、図３（ａ）〜（ｃ）の広角、中間、望遠）、更に該第３群３を別の第３’群５と交換することにより、短焦点端から長焦点端への変倍域外に１点の焦点距離を得ることができる（図１（ｂ）、図４（ｄ）の望遠’）。なお、符号６は絞りである。 Hereinafter, the best mode for carrying out the present invention will be described.
In the following description, f: focal length of the entire system, F: F number, ω: half angle of view, R: radius of curvature, D: surface spacing, Nd: refractive index, νd: Abbe number, K: aspherical A conic constant, A4: fourth-order aspheric coefficient, A6: sixth-order aspheric coefficient, A8: eighth-order aspheric coefficient, A10: tenth-order aspheric coefficient.
However, the aspherical surface used here is defined by the following equation where C is the reciprocal of the paraxial radius of curvature (paraxial curvature) and H is the height from the optical axis.

FIG. 1 is an explanatory diagram showing a configuration of a variable magnification photographing optical system according to the present embodiment, FIG. 2 is an explanatory diagram showing numerical values of the photographing optical system, and FIGS. It is an aberration diagram of the system.
In the present embodiment, the variable magnification photographing optical system is a variable magnification photographing optical system composed of a plurality of groups, and by replacing at least one of the plurality of groups with a group different from the plurality of groups, A focal length outside the range from the short focal end to the long focal end of the variable magnification optical system can be obtained. The present embodiment is a variable magnification photographing optical system comprising this variable magnification photographing optical system and an optical element constituting one or a plurality of groups for exchanging at least one of the plurality of groups.
Specifically, in the examples of FIGS. 1 to 3, the variable magnification photographing optical system is, in order from the object side (left side of FIG. 1), the first group 1 having a positive focal length and the first group 1 having a negative focal length. 2 group 2, a third group 3 having a positive focal length, and a fourth group 4 having a positive focal length, and at least the third group 3 emits light during zooming from the short focal end to the long focal end. By moving on the axis (wide angle, intermediate, telephoto in FIGS. 1 (a), 3 (a) to 3 (c)), and replacing the third group 3 with another third 'group 5, a short One focal length can be obtained outside the zoom range from the focal end to the long focal end (telephoto 'in FIGS. 1B and 4D). Reference numeral 6 denotes an aperture.

In this example, the focal length on the telephoto side from the short focal end to the long focal end of the variable magnification photographic optical system can be obtained by exchanging the third group 3 for the 3 ′ group 5.
The variable magnification shooting optical system
0.6 <| f2 | / f3 <0.8
(Where fi: focal length of the i-th lens group (i = 1 to 3))
Satisfies the following conditional expression.
This conditional expression defines the ratio of the refractive powers of the second group 2 and the third group 3 that are responsible for the main zooming action. When the upper limit of the conditional expression is exceeded, the negative refractive power of the second group 2 is reduced and the refractive power of the third group 3 is also reduced, so that the total lens length is increased. If the lower limit of the conditional expression is exceeded, the negative refractive power of the second group 2 increases, so that high assembling accuracy is required and aberration fluctuations during zooming increase. Therefore, by satisfying this conditional expression, the total lens length is shortened, high assembling accuracy is not required, and aberration fluctuation during zooming is reduced.
The first group 1 is composed of one positive lens. This positive lens is made of a glass material having a refractive index Nd and an Abbe number νd shown below.
Nd> 1.55, νd> 55
This is a conditional expression for satisfactorily correcting the chromatic aberration of magnification that occurs in the present photographing optical system with a large zoom ratio.When the chromatic aberration is exceeded, the chromatic aberration of magnification at the periphery of the screen increases over the entire zoom range. Adversely affects. Therefore, by satisfying this conditional expression, it is possible to reduce the lateral chromatic aberration at the periphery of the screen over the entire zoom range.

The most object side surface of the second lens group 2 is an aspherical surface. By making the most object side surface of the second group 2 an aspherical surface, it becomes possible to efficiently correct distortion, field curvature, and astigmatism on the wide angle side. Various aberrations such as distortion, curvature of field, and astigmatism are corrected by making the ray path effective by aspherical the surface through which the principal ray of the ray bundle incident from outside the optical axis passes far away from the optical axis. Can be operated manually.
The most object side surface of the first lens group 1 is an aspherical surface. When the first lens group 1 is composed of a single lens, it is possible to effectively manipulate the light beam path by forming a desired incident angle corresponding to the light beam angle on the aspherical surface in order to achieve a wide angle of view. Become.
The third group 3 includes a cemented lens. By disposing at least one cemented lens in the third group 3, it is possible to satisfactorily correct spherical aberration on the telephoto side even in the present photographing optical system having a large zoom ratio, and at the same time, it becomes easy to correct lateral chromatic aberration. . In addition, performance degradation due to eccentricity can be suppressed.
Further, the surface closest to the image side (right side in FIG. 1) of the third group 3 is an aspherical surface. By making the most image-side surface of the third group 3 an aspherical surface, the light emitted from the third group 3 that changes with zooming is incident on the fourth group 4 at a desired angle. Can do.
Further, in the variable magnification photographing optical system, focusing is performed in the fourth group 4. Since the zoom imaging optical system mainly uses an electronic imaging device as an object of the imaging plane, it is desirable that the light beam incident on the imaging plane is parallel light. By arranging the fourth group 4 having a positive refractive power in the vicinity of the image plane, this condition can be easily achieved, and the fourth group 4 plays a role of adjusting the entire aberration. By configuring the fourth group 4 with a small number to reduce the weight and using it as a focus group, the focusing speed can be improved. At this time, in order to obtain good photographing performance with a small number of lenses from infinity to a short distance, the use of at least one aspherical surface for this focusing group can increase the degree of freedom of aberration correction, which is desirable. .

FIG. 5 is an explanatory diagram showing a configuration of another example of the variable magnification photographing optical system of the present embodiment, FIG. 6 is an explanatory diagram showing numerical values of the photographing optical system, and FIGS. It is an aberration diagram of the same photographing optical system.
Further, FIG. 9 is an explanatory view showing a configuration of still another example of the variable magnification photographing optical system of the present embodiment, and FIG. 10 is an explanatory view showing respective numerical values of the photographing optical system. FIG. 12 is an aberration diagram of the photographing optical system.
4 to 12 also have the features of the variable magnification photographing optical system described with reference to FIGS. 1 to 4 described above.
Next, a digital camera which is an image pickup apparatus including the variable magnification photographing optical system described above will be described.

13 is a block diagram of electrical connection of the digital camera 11, FIG. 14 is an external perspective view of the digital camera 11, and FIG. 15 is a perspective view of the above-described variable magnification photographing optical system.
The digital camera 11 includes a photographing lens 12 and a light receiving element (area sensor) 13, and is configured to read an image of a photographing object formed by the photographing lens 12 on the light receiving element 13. As the photographing lens 13, the above-described variable magnification photographing optical system is used.
The output from the light receiving element 13 is processed by a signal processing device 15 under the control of the central processing unit 14 and converted into digital information. The image information digitized by the signal processing device 15 is recorded in the semiconductor memory 17 after being subjected to predetermined image processing in the image processing device 16 under the control of the central processing unit 14. An image being shot can be displayed on the liquid crystal monitor 18, and an image recorded in the semiconductor memory 17 can be displayed. The image recorded in the semiconductor memory 17 can be transmitted to the outside using the communication card 19 or the like.

When the digital camera 11 is carried, the taking lens 12 is in a retracted state as shown in FIG. 14A, and when the user operates the power switch 22 to turn on the power, the lens barrel 21 as shown in FIG. 14B. Is paid out. At this time, each group of the photographing lens 12 which is a zoom lens inside the lens barrel 21 has an arrangement of, for example, a short focal end, and the arrangement of each group is changed by operating the zoom lever, to the long focal end. Zooming can be performed. At this time, the viewfinder 20 also zooms in conjunction with the change in the angle of view of the taking lens.
The third group 3 is used for the variable magnification range, and the third 'group 5 is used for the variable magnification range outside. This switching is performed by a predetermined mechanism. In this example, the third group 3 and the third ′ group 5 are accommodated in the cylindrical member 23, and the third group 3 and the third ′ group 5 can be selectively used by rotating the member 23. .

Focusing is performed by pressing the shutter button 24 halfway. This focusing can be performed by moving the fourth group 4 or moving the light receiving element 13. When the shutter button 24 is further pressed, shooting is performed, and thereafter, the processing described above is performed.
When the image recorded in the semiconductor memory 17 is displayed on the liquid crystal monitor 25 or transmitted to the outside using the transmission card 19 or the like, the operation button 26 is used. The semiconductor memory 17 and the communication card 19 are inserted into dedicated or general-purpose slots 27 for use. Reference numeral 28 denotes a flash, and reference numeral 29 denotes a zoom lever.
In the digital camera 11 as described above, since the variable magnification photographing optical system as described above can be used as a photographing lens, high image quality using the light receiving element 13 of 3 to 8 million pixel class. A small camera can be realized.
Or you may make it mount the camera function part of such a digital camera 11 in portable information terminal devices, such as a mobile telephone.

It is explanatory drawing which shows the structure of the variable magnification imaging optical system of this embodiment. It is explanatory drawing which shows each numerical value of the imaging optical system of this embodiment. It is an aberration diagram of the photographing optical system of the present embodiment. It is an aberration diagram of this embodiment. It is explanatory drawing which shows the structure of the other example of the variable magnification imaging optical system of this embodiment. It is explanatory drawing which shows each numerical value of the imaging optical system of this embodiment. It is an aberration diagram of the photographing optical system of the present embodiment. It is an aberration diagram of this embodiment. It is explanatory drawing which shows the structure of the other example of the variable magnification imaging optical system of this embodiment. It is explanatory drawing which shows each numerical value of the imaging optical system of this embodiment. It is an aberration diagram of the photographing optical system of the present embodiment. It is an aberration diagram of this embodiment. It is a block diagram of the electrical connection of the digital camera of this embodiment. 1 is an external perspective view of a digital camera according to an embodiment. 1 is a perspective view of a variable magnification photographing optical system used for a digital camera of the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st group 2 2nd group 3 3rd group 4 4th group 11 Imaging device

Claims (13)

In a variable magnification photographing optical system having a variable magnification photographing optical system composed of a plurality of groups,
An optical element that is a group different from the plurality of groups to be exchanged for at least one of the plurality of groups;
Obtaining a focal length outside the range from the short focal end to the long focal end by the exchange;
A variable magnification optical system characterized by this. The plurality of groups in order from the object side are a first group having a positive focal length, a second group having a negative focal length, a third group having a positive focal length, and a fourth group having a positive focal length. A group,
At least the third group moves on the optical axis upon zooming from the short focal end to the long focal end,
By exchanging the third group with a third 3 ′ group serving as the optical element, a focal length of one point can be obtained outside the zoom range from the short focal end to the long focal end.
The variable magnification photographing optical system according to claim 1.   3. The variable magnification photographing optical system according to claim 2, wherein the focal length on the telephoto side from the long focal end can be obtained from the short focal end by the exchange.   4. The variable magnification photographing optical system according to claim 2, wherein the first group includes a single positive lens. 5. 0.6 <| f2 | / f3 <0.8
(Where fi: focal length of the i-th lens group (i = 1 to 3))
The zoom lens system according to any one of claims 2 to 4, wherein the following conditional expression is satisfied. When the positive lens constituting the first group has a refractive index Nd and an Abbe number νd,
Nd> 1.55, νd> 55
5. The zoom lens system according to claim 4, wherein the zoom lens system is made of a glass material that satisfies the above condition.   The zoom lens system according to any one of claims 2 to 6, wherein the most object-side surface of the second group is an aspherical surface.   7. The variable magnification photographing optical system according to claim 4, wherein the most object-side surface of the first group is an aspherical surface.   The variable magnification photographing optical system according to any one of claims 2 to 8, wherein a cemented lens is included in the third group.   10. The zoom lens system according to claim 2, wherein the most image-side surface of the third group is an aspherical surface.   The variable magnification imaging optical system according to any one of claims 2 to 10, wherein focusing is performed in the fourth group. A variable magnification photographing optical system system according to any one of claims 1 to 11,
The zooming optical system includes an exchange mechanism, and switches the zooming range from the wide angle to the telephoto and the focal length outside the zooming range by the replacement. A variable magnification photographing optical system according to any one of claims 1 to 11 is provided in a camera function unit,
The variable magnification photographing optical system includes a mechanism for performing the replacement, and switches the zoom range from a wide angle to the telephoto and the focal length outside the zoom range by the replacement.

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