JP2005284063A - Four-group zoom lens with vibration-proof function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a four-group zoom lens with a vibration-proof function in which a deterioration in optical performance due to vibration-proofing operation is suppressed and also the saving of power required for driving control and excellent followup ability to the vibration are attained. <P>SOLUTION: The four-group zoom lens with the vibration-proof function is constituted of a 1st positive lens group G<SB>1</SB>, a 2nd negative lens group G<SB>2</SB>, a 3rd negative lens group G<SB>3</SB>, and a 4th positive lens group G<SB>4</SB>including a diaphragm 3 from an object side. In the 4th lens group G<SB>4</SB>, a 4a positive lens group G<SB>4a</SB>(front group) and a 4b positive lens group G<SB>4b</SB>(rear group) are disposed to be opposed while holding the widest space (D<SB>30</SB>) in the 4th lens group G<SB>4</SB>made nearly afocal in between. One positive lens L<SB>22</SB>nearest to an image side in the 4b lens group G<SB>4b</SB>(rear group) is driven to move back and forth in a direction orthogonal to an optical axis X so as to correct the deviation of an image position in a lateral direction caused by the vibration such as camera shake or the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a four-unit zoom lens with an anti-vibration function suitable for a video camera, a digital camera, etc., and more particularly to a four-group zoom lens having an anti-vibration function capable of suppressing the occurrence of image blur due to vibrations such as camera shake. is there.

  In a four-group zoom lens composed of positive, negative, negative, and positive lens groups in order from the object side, image blur (image position) is achieved by moving some of the lens groups in a direction perpendicular to the optical axis. (Patent Documents 1, 2, 3, etc.) have been proposed in the following patent documents. However, in the four-group zoom lens having the image stabilization function disclosed in these publications, Thus, the first lens group located closest to the object side is driven as an anti-vibration lens group in a direction substantially orthogonal to the optical axis.

  However, in general, since the first lens group is large in size and heavy, those described in Patent Documents 1, 2, and 3 require a great amount of power for driving and controlling the vibration-proof lens group and follow the vibration. There is a problem in terms of sex.

Therefore, the techniques described in the following Patent Documents 4, 5, and 6 are known as techniques for solving such problems. That is, those described in the following Patent Documents 4, 5, and 6 are arranged in the fourth lens group through the maximum interval, and both of the front group and the rear group having positive refractive power are arranged in front of each other. This is a zoom lens having an anti-vibration function by reciprocally driving the entire group or a part thereof in a direction substantially perpendicular to the optical axis.
In addition, there is also known an anti-vibration function provided by reciprocally driving the entire rear group of the fourth lens group in a direction substantially orthogonal to the optical axis.

JP-A-1-284823 JP-A-1-284824 JP-A-1-284825 JP-A-8-29738 JP 2001-281546 A JP 2002-287030 A

  However, according to those described in Patent Documents 4, 5, and 6, the front group of the fourth lens group, which is a part where the angle of the light beam greatly changes, is the anti-vibration lens group, and the anti-vibration effect is great, but the aberration The fluctuation of the optical performance is large, and the deterioration of the optical performance due to it is a big problem.

  Further, using the entire rear group as an anti-vibration lens group has a small aberration variation and an effect of suppressing deterioration of optical performance, but the rear group is generally composed of a plurality of lenses. A large amount of power is required for driving control of the anti-vibration lens group, and there is also a problem in terms of followability to vibration.

  The present invention has been made in view of such circumstances, and can suppress deterioration in optical performance associated with the image stabilization operation, achieve power saving required for drive control and good followability to vibration. An object of the present invention is to provide a four-group zoom lens with an anti-vibration function.

The four-unit zoom lens with an image stabilization function according to the present invention includes, in order from the object side, a first lens unit having a positive refractive power that is fixed at the time of zooming, continuous zooming, and image plane movement caused by the continuous zooming. A second lens group having a negative refractive power that performs correction and moves in relation to each other, a third lens group having a negative or positive refractive power, and a fourth lens having a positive refractive power that is fixed at the time of zooming. An array of lens groups,
The fourth lens group is configured to move the most image side lens in a direction intersecting the optical axis so as to correct image blur.

  The fourth lens group includes, in order from the object side, the 4a lens group having a positive refractive power and the 4b lens group having a positive refractive power in order from the object side through the longest air gap in the fourth lens group. The fourth lens group is composed of a plurality of lenses.

Furthermore, it is preferable that the following conditional expression (1) is satisfied in the above-described four-group zoom lens with an image stabilization function.
1.5 <fe / Bf <3.0 (1)
However,
Bf: Back focus of all lens systems
fe: Focal length of the lens on the most image side in the fourth lens unit

  As described above, according to the four-group zoom lens with an image stabilization function of the present invention, by moving one lens located closest to the image side of the fourth lens group in the direction crossing the optical axis, The lateral displacement of the image position due to vibration such as blurring is corrected.

Since the lens located closest to the image side of the fourth lens group is a part where the angle of the light beam generally changes smaller than the lens located on the object side of the fourth lens group, the aberration of the anti-vibration drive is reduced. There is little fluctuation, and deterioration of optical performance can be suppressed.
In particular, in the case where the fourth lens group is a system composed of a front group and a rear group that face each other with a substantially afocal air gap, the lens on the most image side is included in the rear group. Is located at a site where the angle changes extremely small, variation in aberrations during vibration isolation driving is extremely small, and degradation of optical performance can be significantly suppressed.

  In addition, since the anti-vibration function is performed by a single lens, the driving load is reduced, and power saving required for driving control and good followability to vibration can be achieved.

Hereinafter, a 4-group zoom lens with an image stabilization function according to an embodiment of the present invention will be described with reference to the drawings.

<Example 1>
A four-group zoom lens with a vibration-proof function (state at the wide-angle end) according to Example 1 shown in FIG. 1 is attached to the object side of the color separation optical system 2 of a video television camera, for example.

This four-group zoom lens with an anti-vibration function has a four-group configuration and is a zoom lens composed of ₂₂ lenses L _{1 to} L ₂₂ , and the second lens group G ₂ and the third lens group at the time of zooming. the lens group G ₃ is moved along the optical axis X, along with changing the focal length f of the whole system by changing the predetermined lens group spacing, efficiently luminous flux at an imaging position on the image plane 1 This zoom lens is made to converge. In addition, the movement locus | trajectory of a moving lens group when it goes to a telephoto end from a wide angle end is shown by the lower part of FIG.

That is, as shown in FIG. 1, the four-group zoom lens with an image stabilization function according to the first embodiment includes five positive first lens groups G ₁ including _six lenses L _{1 to} L ₆ from the object side. A negative second lens group G ₂ composed of lenses L _{7 to} L ₁₁ , a negative third lens group G ₃ composed of two lenses L ₁₂ and L ₁₃ , and a diaphragm 3 and nine lenses L _{14 to} L ₂₂ and a positive fourth lens group _{G 4} consisting of, also, the fourth lens group _{G 4} is squeezed 3 and three lenses _L 14 consisting _{~L 16} positive. 4a lens group _{G 4a} (front group), And a positive fourth b lens group G _4b (rear group) consisting of six lenses L _{17 to} L ₂₂ sandwiches the widest distance (D ₃₀ ) in the fourth lens group G ₄ that is substantially afocal. Are arranged so as to face each other.

Further, the one positive lens L ₂₂ closest to the image side of the fourth lens group G _4b (rear group) is accompanied by vibrations such as camera shake in a direction perpendicular to the optical axis X (direction of arrow A). It is configured to be reciprocated so as to correct a lateral shift of the image position.
Thus, the fourth lens group G _4, via a substantially afocal air gap, positive first 4a lens group G _{4a (front} group) which faces each other and the positive of the 4b lens group G _{4b (rear} group ), The positive lens L ₂₂ functioning as an anti-vibration lens is located at a portion where the angle of the light beam changes extremely small, and therefore, the variation in aberration during the anti-vibration driving is extremely large. It is small, and deterioration of optical performance can be greatly suppressed.

Further, at the time of image stabilization drive for may be driven controls one lens L _22, the load is reduced, it is possible to achieve good followability to labor saving and vibration of the power required for driving control.

In the 4-group zoom lens with an image stabilization function of the first embodiment, when the back focus of the entire lens system is Bf and the focal length of the lens (L ₂₂ ) that is moved for image stabilization is fe, The following conditional expression (1) is satisfied.
1.5 <fe / Bf <3.0 (1)
The conditional expression (1) is intended to define the most image-side power of the lens L ₂₂ in the fourth lens group G _4, its power, to move the image to the extent that it is possible to achieve a vibration reduction function This is a range that is sufficient to suppress aberration fluctuations to an allowable range.

That is, if the upper limit of the above equation (1) is exceeded, the amount of lens movement necessary for image shift correction becomes large. On the other hand, if the lower limit is exceeded, the eccentricity of the lens L ₂₂ associated with the image stabilization drive is increased. The aberration fluctuation at the time becomes large.

Since the lens L ₂₂ closest to the image side in the fourth lens group G ₄ is a positive lens, the lens L ₂₂ generates strong spherical aberration in the negative direction. If the number of the above equation (1) is approximately 1, that is, when the focal length fe of the entire lens system back focus Bf and the lens L ₂₂ is of the same order, to the screen center to move perpendicular to the optical axis (horizontal) direction of a light beam, the object side of the lens L _22, and substantially parallel to the optical axis X, distribution ratio of the lens L ₂₂ in the spherical aberration correction becomes too large, the optical axis X and the vertical (horizontal) in the direction Degradation of performance due to movement is large.

  The means for performing anti-vibration driving includes a vibration detecting unit that detects vibration of the zoom lens system, a driving unit that reciprocates the anti-vibration lens along a direction orthogonal to the optical axis, and an output from the vibration detecting unit. And a control unit that controls the drive unit so as to correct the image shift due to vibration. For example, each of the above-described publications has a well-known configuration.

  Here, in Example 1, the radius of curvature R (mm) of each lens surface, the center thickness of each lens, and the air spacing between the lenses (hereinafter collectively referred to as the axial top surface spacing) D (mm), Table 1 below shows the values of the refractive index N and the Abbe number ν at the e-line of the lens. In Table 1, surfaces 41, 42, and 43 represent the surfaces of the color separation optical system 2. In the column in which the distance between the lens groups is changed, “Variable 1,” “Variable 2” and “Variable 3” are described. Further, the column with “**” means that it can be changed during back focus adjustment. (Same as in Example 2 and conventional example). The numbers in the table represent the order from the object side (the same applies in the second embodiment and the conventional example).

Further, the screen size in the first embodiment is φ11.0, and the focal length, the open F value at the wide angle end (WIDE) and the telephoto end (TELE), the variable 1, 2, 3 in Table 1 are set. value, the back focus Bf, the value of the focal length fe and fe / Bf lens _{L 22} shown in Table 2.

Table 3 shows a comparison of the amount of movement of each lens of the 4b lens group G _4b required to shift the image position by 0.1 mm in the direction perpendicular to the optical axis X. That is, the entire 4b lens group G _4b (the entire 4b: comparison data 2), the lens L ₁₇ (4b-1: comparison data 3), and the cemented lens of the lens L ₁₈ and the lens L ₁₉ (4b-2: comparison data 4) , lenses cemented lens _{L 20} and the lens _{L 21} (4b-3: Comparative data 5) and the lens _L 22: shows the amount of movement (4b-4 of example 1).

4A to 4F show the comparative data 2 to 5 and Example 1 when the lens is not moved at the wide-angle end of the above-mentioned anti-vibration 4-group zoom lens (Comparative Data 1). FIG. 6 is a top and bottom coma aberration diagram at a 60% image height when the lens movement according to FIG.
As is apparent from FIG. 4, according to the four-group zoom lens with the image stabilization function according to the first embodiment, coma aberration that is as good as or better than when the entire 4b lens group G _4b is moved. it can.

<Example 2>
A four-group zoom lens with a vibration-proof function (state at the wide-angle end) according to Example 2 shown in FIG. 2 is attached to the object side of the color separation optical system 2 of the video television camera, for example.

This 4-group zoom lens with an image stabilization function has a 4-group configuration similar to that of the first embodiment, and is a zoom lens composed of ₁₇ lenses L _{1 to} L ₁₇ . the second lens group G ₂ and the third lens group G ₃ is moved along the optical axis X, along with changing the focal length f of the whole system by changing the predetermined lens group spacing, the image plane of the light beam 1 is a zoom lens that is efficiently converged to an image forming position on 1. In addition, the movement locus | trajectory of a moving lens group when it goes to a telephoto end from a wide angle end is shown by the lower part of FIG.

As shown in FIG. 2, the four-unit zoom lens with an image stabilization function according to the second embodiment includes a positive first lens group G ₁ including three lenses L _{1 to} L ₃ and _three lenses L from the object side. _A negative second lens group G ₂ composed of _{4 to} L ₆ , a negative third lens group G ₃ composed of two lenses L ₇ and L ₈ , and a diaphragm 3 and nine lenses L _{9 to} L _17. and a positive fourth lens group _{G 4,} also, the fourth lens group _{G 4} is squeezed 3 to consist of four lenses _L 9 _{~L 12} positive. 4a lens group _{G 4a} (front group), and 5 A positive fourth b lens group G _4b (rear group) consisting of a plurality of lenses L _{13 to} L ₁₇ is paired across the widest distance (D ₂₁ ) in the fourth lens group G ₄ which is substantially afocal. It is arranged so that

In addition, one positive lens L ₁₇ closest to the image side of the fourth b lens group G _4b (rear group) is accompanied by vibrations such as camera shake in a direction perpendicular to the optical axis X (direction of arrow A). It is configured to be reciprocated so as to correct a lateral shift of the image position.

Thus, the fourth lens group G _4, via a substantially afocal air gap, positive first 4a lens group G _{4a (front} group) which faces each other and the positive of the 4b lens group G _{4b (rear} group ), The positive lens L ₁₇ functioning as an anti-vibration lens is located at a portion where the angle of the light beam changes extremely small, and therefore the variation in aberration during the anti-vibration driving is extremely large. It is small, and deterioration of optical performance can be greatly suppressed.
Further, at the time of image stabilization drive for may be driven controls one lens L _17, the load is reduced, it is possible to achieve good followability to labor saving and vibration of the power required for driving control.

In addition, the four-unit zoom lens with an image stabilization function of Example 2 is configured to satisfy the conditional expression (1).
Here, in Example 2, the radius of curvature R (mm) of each lens surface, the center thickness of each lens, and the air spacing between the lenses (hereinafter collectively referred to as the axial top surface spacing) D (mm), Table 4 below shows the values of the refractive index N and the Abbe number ν at the e-line of the lens. In Table 4, surfaces 30, 31, and 32 represent the surfaces of the color separation optical system 2.

The screen size in Example 2 is φ8.0, and the focal length, open F value, and variable 1, 2, and 3 in Table 4 at the wide-angle end (WIDE) and the telephoto end (TELE). value, the back focus Bf, the value of the focal length fe and fe / Bf lens _{L 17} shown in Table 5.

Table 6 shows a comparison of the amount of movement of each lens of the 4b lens group G _4b required to shift the image position by 0.1 mm in the direction perpendicular to the optical axis X. In other words, the 4b lens group _{G 4b} whole (entire 4b: Comparison data 2), a cemented lens of the lens _{L 13} and a lens _{L 14} (4b-1: Comparative data 3), a cemented lens (4b of the lens _{L 15} and a lens _{L 16} -2: Indicates the movement amount of the comparison data 4) and the lens L ₁₇ (4b-3: Example 2).

5A to 5E show the comparison data 2 to 4 and the example 2 when the lens is not moved at the wide-angle end of the above-described four-group zoom lens with an image stabilization function (comparison data 1). FIG. 6 is a top and bottom coma aberration diagram at a 60% image height when the lens movement according to FIG.
As is apparent from FIG. 5, according to the four-unit zoom lens with an image stabilization function according to the second embodiment, coma aberration that is as good as or better than when the entire 4b lens group G _4b is moved. it can.

<Conventional example>
The 4-group zoom lens with the image stabilization function (state at the wide-angle end) according to the conventional example shown in FIG. 3 corresponds to the conventional example of the present invention, and the image stabilization function is the 4b lens group G _4b (rear) The group) as a whole.

That is, this anti-vibration 4-group zoom lens has a 4-group configuration similar to those in the above embodiments, and is a zoom lens composed of ₂₁ lenses L _{1 to} L _21. in times when the second lens group G ₂ and the third lens group G ₃ is moved along the optical axis X with changing the focal length f of the whole system by changing the predetermined lens group spacing, forming a light beam This is a zoom lens that efficiently converges to an image forming position on the image plane 1. In addition, the movement locus | trajectory of a moving lens group in the case of heading from a wide angle end to a telephoto end is shown by the lower part of FIG.

As shown in FIG. 3, the conventional four-unit zoom lens with an anti-vibration function includes a positive first lens group G ₁ composed of _five lenses L _{1 to} L ₅ and four lenses L ₆ from the object side. Negative second lens group G ₂ composed of ˜L ₉ , negative third lens group G ₃ composed of two lenses L ₁₀ , L ₁₁ , and positive composed of a diaphragm 3 and ten lenses L ₁₂ ˜L ₂₁ and a fourth lens group _{G 4,} and also, the fourth lens group _{G 4} is squeezed 3 and 4 lenses _L 12 _{~L 15} positive. 4a lens group _{G 4a} (front group) consisting of, and six The positive fourth b lens group G _4b (rear lens group) consisting of the lenses L _{16 to} L ₂₁ of the fourth lens group G _{4b and} the positive fourth lens group G _4b (rear group) are opposed to each other across the widest distance (D ₂₉ ) in the fourth lens group G ₄ that is substantially afocal. It is arranged to do.

Further, as described above, the entire 4b lens group G _4b (rear group) reciprocates in the direction orthogonal to the optical axis X so as to correct the lateral displacement of the image position caused by vibration such as camera shake. It is configured to be driven.

  Here, in the conventional example, the radius of curvature R (mm) of each lens surface, the center thickness of each lens, and the air spacing between the lenses (hereinafter collectively referred to as the axial top surface spacing) D (mm), each lens Table 7 below shows the values of the refractive index N and the Abbe number ν at the e-line. In Table 7, surfaces 40, 41, and 42 represent the surfaces of the color separation optical system 2.

  The screen size in this conventional example is φ11.0, and the focal length, open F value, and variable 1, 2, and 3 values in Table 7 at the wide angle end (WIDE) and the telephoto end (TELE). Table 8 shows the back focus Bf.

Table 9 shows the amount of movement of the entire 4b lens group _G4b (the entire 4b group) required to shift the image position by 0.1 mm in the direction perpendicular to the optical axis X.

FIGS. 6A and 6B show lenses when the lens is not moved at the wide-angle end of the above-described anti-vibration 4-group zoom lens and when the entire 4b lens group G _4b (rear group) is involved. It is an upper and lower coma aberration figure in 60% image height at the time of moving.
As can be seen from FIG. 6, although the coma aberration can be improved also by the conventional four-group zoom lens with an anti-vibration function, as shown in FIG. 3, the six lenses L ₁₆ since the 4b lens group G _4b consisting ~L ₂₁ a _(rear group) is driven for image stabilization, the power increases required for the drive, also a disadvantage in terms of responsiveness to vibration such as camera shake .

1 is a schematic diagram showing a lens configuration of a four-group zoom lens with an image stabilization function according to Embodiment 1 of the present invention. FIG. Schematic which shows the lens structure of the 4 group zoom lens with a vibration proof function which concerns on Example 2 of this invention. Schematic which shows the lens structure of the 4 group zoom lens with a vibration proof function which concerns on a prior art example. Coma aberration diagram of the lens according to Example 1 of the present invention Coma aberration diagram of the lens according to Example 2 of the present invention Coma aberration diagram of lenses according to conventional examples

Explanation of symbols

L ₁ ~L ₂₂ lens R ₁ to R of curvature of ₄₄ the lens surface radius D ₁ to D ₄₃ lens spacing (lens thickness)
X Optical axis 1 Imaging surface 2 Color separation optical system 3 Shutter (aperture)

Claims (3)

In order from the object side, negative refraction that moves positively with the first lens unit having a positive refractive power, which is fixed at the time of zooming, and continuous zooming and correction of image plane movement caused by the continuous zooming. A second lens group having power, a third lens group having negative or positive refracting power, and a fourth lens group having positive refracting power, which are fixed at the time of zooming,
A four-group zoom lens with an anti-vibration function, wherein the lens on the most image side in the fourth lens group is moved in a direction intersecting the optical axis so as to correct image blur.   The fourth lens group includes a 4a lens group having a positive refractive power and a 4b lens group having a positive refractive power in order from the object side via the longest air gap in the fourth lens group. 2. The four-group zoom lens with an image stabilization function according to claim 1, wherein the fourth lens group includes a plurality of lenses. The four-unit zoom lens with an image stabilizing function according to claim 1 or 2, wherein the following conditional expression (1) is satisfied.
1.5 <fe / Bf <3.0 (1)
However,
Bf: Back focus of all lens systems
fe: Focal length of the lens on the most image side in the fourth lens unit

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