JP2002162563A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact vibration-proof zoom lens, constituted of five groups and is set so that the moving amount of a correction lens group (3rd lens group) at camera shake is small and the deterioration of optical performance is small. SOLUTION: This zoom lens is equipped with five lens groups, arranged in the order starting from the object side to the image surface side, that is, a 1st lens group 1 having positive refractive power and fixed, a 2nd lens group 2 having negative refractive power and performing variable power operation by moving on the optical axis, a 3rd lens group 3 having positive refractive power and fixed with respect to an image surface, a 4th lens group 4 having negative refractive power and moving on the optical axis, so that the image surface fluctuated by variable power or the change of an object distance is kept at a constant position from a reference surface and a 5th lens group 5 having positive refractive power and fixed. By moving the 3rd lens group 3 as a whole in a direction perpendicular to the optical axis, fluctuations of the image at camera shake is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens which is used in a video camera or a digital still camera and has a camera shake correction function for optically correcting image shake caused by camera shake or vibration.

[0002]

2. Description of the Related Art Hitherto, various anti-vibration optical systems having an anti-shake function for preventing vibration such as camera shake have been proposed.
For example, in Japanese Patent Application Laid-Open No. 9-230234,
A zoom lens in which a variable apex angle prism is disposed inside an optical system has been proposed, and thereby a variation in an image due to camera shake or the like is corrected. In addition, a still image can be obtained relatively easily by using the variable apex angle prism.

[0003] In Japanese Patent Application Laid-Open No. 11-31742, there are four lenses having positive, negative, positive, and positive refractive power, respectively.
In a four-group zoom lens composed of two lens groups, image stabilization is performed by moving the entire third lens group perpendicular to the optical axis. The entire third lens group fixed to the image plane during zooming and focusing is moved perpendicularly to the optical axis to perform image stabilization, so that the third lens group is small and lightweight, and chromatic aberration is reduced. A small zoom lens can be obtained.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 9-2
In an optical system using a variable apex angle prism as proposed in Japanese Patent No. 30234 or the like, the amount of chromatic aberration of magnification due to eccentricity increases on the telephoto side during camera shake. Further, a space for inserting the variable apex angle prism is required, and the entire optical length is increased, which is disadvantageous for reduction in size and weight. Further, there is a problem that a drive angle required for image stabilization is increased depending on a place where the variable apex angle prism is disposed.

In a four-group zoom lens proposed in Japanese Unexamined Patent Publication No. 11-31742, which includes four lens groups having positive, negative, positive, and positive refractive powers, respectively, a third lens group is provided. When camera shake correction is performed by moving the entirety perpendicular to the optical axis, if a compact optical system having a small combined paraxial lateral magnification of the third lens unit and the fourth lens unit is to be formed, the correction of the third lens unit is performed. The sensitivity was small, and the amount of movement of the third lens group in the direction perpendicular to the optical axis tended to be too large. In the case of shift-type image stabilization, the peripheral light flux is determined by the front group and the rear group of the shift lens group (correction lens group). Therefore, especially on the telephoto side where the shift amount is large, the amount of light around the screen during image stabilization. There was a problem that the change became large and unsightly.
In addition, since the amount of movement of the correction lens group is large, there is also a problem that the amount of occurrence of eccentric aberration during image stabilization increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and in a zoom lens having a five-group structure, a third lens which is fixed with respect to an image plane during zooming and focusing. When correcting the camera shake by moving the lens group perpendicular to the optical axis, the amount of movement of the correction lens group (third lens group) at the time of camera shake can be reduced by appropriately setting the refractive power arrangement of the third lens group. An object of the present invention is to provide a compact anti-vibration zoom lens which is reduced in size and has little deterioration in optical performance.

[0007]

In order to achieve the above object, a zoom lens according to the present invention has a configuration in which a positive refractive power and a fixed refractive power are arranged in order from an object side to an image plane side. A first lens group having a negative refractive power, and a second lens group performing a zooming action by moving on the optical axis;
A third lens group having a positive refractive power and fixed with respect to the image plane, and an image plane having a negative refractive power and fluctuating due to zooming or a change in object distance is placed at a fixed position from the reference plane. A fourth lens group that moves on the optical axis to keep it, and has a positive refractive power;
A zoom lens comprising a fixed fifth lens group, wherein the third lens group is moved perpendicularly to the optical axis, whereby image fluctuations during camera shake are corrected, and When the axial lateral magnification is β3, the paraxial lateral magnification of the fourth lens group is β4, and the paraxial lateral magnification of the fifth lens group is β5, the following expression (3) is satisfied. I do. [Equation 3] 1.5 <(1−β3) · β4 · β5 <2.5 According to the configuration of the zoom lens, a high-performance zoom lens that is compact and has a camera shake correction function can be realized. That is, by appropriately setting the refractive power of each lens group (the third to fifth lens groups), the amount of movement of the third lens group during camera shake correction can be reduced. Deterioration is reduced, and fluctuations in the peripheral light amount can be suppressed. (1-
If β3) .beta.4.beta.5 is 1.5 or less, the amount of movement of the third lens group becomes too large. On the other hand, (1-β3)
When β4 · β5 is 2.5 or more, the amount of movement of the third lens group is reduced, but the eccentric sensitivity is increased, and the remaining amount of the vibration reduction due to the influence of the mechanical error increases.

In the zoom lens system according to the present invention, the third lens group includes one positive lens and one positive lens.
It preferably includes a cemented lens with two negative lenses. According to this preferred example, it is possible to effectively correct chromatic aberration at the time of rest or at the time of camera shake correction. In this case, when the Abbe number of the positive lens constituting the cemented lens is ν31 and the Abbe number of the negative lens is ν32, it is preferable that the following expression (4) is satisfied. [Equation 4] ν31−ν32> 25 According to this preferred example, fluctuations in chromatic aberration of magnification can be reduced during camera shake correction, so that a high-performance zoom lens with small performance degradation can be realized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments.

FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the embodiment. As shown in FIG. 1, the zoom lens according to the present embodiment includes a first lens group 1 arranged in order from an object side (left side in FIG. 1) to an image plane side (right side in FIG. 1). , The second lens group 2, the stop S, and the third lens group 3.
And a fourth lens group 4, a fifth lens group 5, and a flat glass EG optically equivalent to a cover glass or a low-pass filter of the image sensor.

The first lens group 1 has a positive refractive power and is in a fixed state. The second lens group 2 has a negative refractive power, and performs a zooming action by moving on the optical axis.
The third lens group 3 has a positive refractive power and is in a state fixed to the image plane. The fourth lens group 4 has a negative refractive power and moves on the optical axis so as to keep the image plane, which fluctuates due to zooming or a change in object distance, at a fixed position from the reference plane.
The fifth lens group 5 has a positive refractive power and is in a fixed state.

The first lens group 1 includes a negative lens 1a, a positive lens 1b, and a positive meniscus lens 1c having a convex surface facing the object side, which are arranged in order from the object side. The second lens group 2 includes a negative lens 2a, and a cemented lens of a biconcave lens 2b and a positive lens 2c, which are arranged in order from the object side. The third lens group 3 includes a first positive lens 3a and a second
And a cemented lens of the positive lens 3b and the negative lens 3c. The fourth lens group 4 is composed of a cemented lens of a negative lens 4a and a biconcave lens 4b arranged in order from the object side. The fifth lens group 5 includes, in order from the object side, a cemented lens of a negative lens 5a and a first positive lens 5b, and a second positive lens 5c.

In the zoom lens of the present embodiment,
By moving the third lens group 3 perpendicular to the optical axis,
The image fluctuation at the time of camera shake is corrected. When the paraxial lateral magnification of the third lens group 3 is β3, the paraxial lateral magnification of the fourth lens group 4 is β4, and the paraxial lateral magnification of the fifth lens group 5 is β5,
The following condition (Equation 5) is satisfied. [Equation 5] 1.5 <(1−β3) · β4 · β5 <2.5 According to the configuration of the present embodiment, a compact and high-performance zoom lens having a camera shake correction function is realized. Can be. That is, by appropriately setting the refractive power of each of the lens groups (the third to fifth lens groups 1 to 5), the amount of movement of the third lens group 3 during camera shake correction can be reduced. The deterioration of the optical performance is reduced, and the fluctuation of the peripheral light amount can be suppressed to be small. If (1−β3) · β4 · β5 is 1.5 or less, the amount of movement of the third lens group 3 becomes too large. On the other hand, when (1−β3) · β4 · β5 becomes 2.5 or more,
Although the amount of movement of the third lens group 3 is small, the sensitivity to eccentricity is large, and the remaining amount of correction for image stabilization due to the influence of a mechanical error is large.

In the zoom lens according to the present embodiment, when the Abbe number of the second positive lens 3b constituting the cemented lens of the third lens group 3 is ν31 and the Abbe number of the negative lens 3c is ν32, It is desirable that the following condition (Equation 6) is satisfied. [Equation 6] ν31−ν32> 25 By satisfying the condition of (Equation 6), it is possible to reduce the fluctuation of the chromatic aberration of magnification at the time of camera shake correction, and as a result, to realize a high-performance zoom lens with a small decrease in performance. be able to.

The object-side surface (the twelfth surface) of the first positive lens 3a constituting the third lens group 3 is an aspheric surface, and the aspheric shape is represented by the following (Formula 7). You. [Equation 7] x = (h ² / r) / (1+ (K + 1) h ² / r ² ) ^1/2
+ Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ where x is the optical axis direction, h is the distance from the optical axis, r is the radius of curvature of the reference sphere, and aspheric coefficients K, A, B, C, and D are As shown in 1).

The following (Table 1) shows specific numerical examples of the zoom lens according to the present embodiment. [Table 1] f = 5.78 to 54.8 F / 2.10 to F / 2.68 r 1 47.993 d 1 1.000 n 1 1.84666 ν 1 23.8 r 2 24.350 d 2 4.800 n 2 1.60311 ν 2 60.6 r 3 -96.343 d 3 0.120 r 4 20.818 d 4 2.900 n 3 1.60311 ν 3 60.6 r 5 56.051 d 5 Variable r 6 41.131 d 6 0.650 n 4 1.80420 ν 4 46.6 r 7 8.017 d 7 3.006 r 8 -9.751 d 8 0.600 n 5 1.72916 ν 5 54.7 r 9 7.282 d 9 2.700 n 6 1.80518 ν 6 25.4 r10 488.086 d10 Variable r11 Aperture d11 1.009 r12 * 20.031 d12 2.600 n 7 1.60602 ν 7 57.5 r13 −27.885 d13 0.120 r14 35.981 d14 2.600 n 8 1.69680 ν 8 55.6 r15 −8.643 d15 0.600 n 9 1.84666 ν 9 23.8 r16 −19.588 d16 Variable r17 −31.292 d17 1.800 n10 1.80518 ν10 25.5 r18 −10.088 d18 0.600 n11 1.72916 ν11 54.7 r19 17.412 d19 Variable r20 89.987 d20 0.600 n12 1.84666 ν12 23.8 r21 10.942 d21 3.050 n13 1.5182221313. 0.120 r23 14.606 d23 2.150 n14 1.54072 ν14 47.2 r24 3323.510 d24 4.000 r25 ∞ d23 3.300 n15 1.51633 ν15 64.3 r26 可 変 Variable interval: fd 5 d10 d16 d19 5.78 0.704 18.627 1.350 7.424 27.9 13.6 01 5.730 5.294 3.481 54.8 17.794 1.536 1.350 7.424 Twelveth surface aspheric coefficient K −1.9129 A −6.61857 × 10 ^-3 B −4.61973 × 10 ^-5 C 4.22058 × 10 ^-6 D −6.36147 × 10 ^-8 Above (Table 1) , R1, r2,... (Mm) are the radii of curvature of the respective surfaces of the lens counted in order from the object side, d1, d
2,... (Mm) is the thickness of each lens counted from the object side or the air gap between each lens, and n1, n2,. ,
.. are the Abbe numbers of each lens with respect to the d-line counted in order from the object side, f is the focal length of the entire system, and F / is F
Indicates a number.

In the zoom lens having the specifications shown in Table 1 above, the shift sensitivity of the third lens unit 3 in the direction perpendicular to the optical axis is defined by (1−β3) · β4 · β5 = 1.70. , (5) is satisfied. Further, the Abbe number ν31 of the second positive lens 3b and the Abbe number ν of the negative lens 3c that constitute the cemented lens of the third lens group 3
The difference (ν31−ν32) from 32 is 31.8, which satisfies the condition of (Equation 6).

FIGS. 2 to 4 show the zoom lens according to the present embodiment at a wide-angle end (wide end), an intermediate position (normal position),
FIG. 4 shows an aberration performance diagram at the telephoto end (telephoto end) at rest.
In each figure, F indicates a value for the F line, and C indicates a value for the C line. In each figure, S indicates sagittal field curvature, and M indicates meridional field curvature. Ω (゜) indicates the angle of view of incidence.

FIG. 5 shows an aberration performance diagram at the telephoto end when correcting by 0.5 °. In FIG. 5, the solid line is the d line,
The short broken line shows the value for the F line, and the long broken line shows the value for the C line.

As is apparent from these aberration performance diagrams (FIGS. 2 to 5), it is understood that the zoom lens according to the present embodiment can realize good optical performance with small aberration.

[Second Embodiment] FIG. 6 shows a second embodiment of the present invention.
FIG. 3 is a layout diagram showing a configuration of a zoom lens according to the embodiment. As shown in FIG. 6, the zoom lens according to the present embodiment includes a first lens group 6 arranged in order from the object side (the left side in FIG. 6) to the image plane side (the right side in FIG. 6). , The second lens group 7, the aperture S, and the third lens group 8
, A fourth lens group 9, a fifth lens group 10, and a flat glass EG optically equivalent to a cover glass or a low-pass filter of the image sensor.

The first lens group 6, the third lens group 8, and the fourth lens group 9 are the same as the first lens group 1, the third lens group 3, and the fourth lens group 4 in the first embodiment, respectively. It has a configuration and works the same way. That is, in FIG.
6a, 6b and 6c correspond to 1a, 1b and 1c in FIG. 1, respectively, and 8a, 8b and 8c correspond to 3a and 3 in FIG.
b, 3c, and 9a, 9b correspond to 4a,
4b.

The second lens group 7 has a negative refracting power, and performs a zooming operation by moving on the optical axis. The fifth lens group 10 has a positive refractive power and is in a fixed state.

The second lens group 7 is composed of a first negative lens 7a, a cemented lens of a biconcave lens 7b and a positive lens 7c, and a second negative lens 7d arranged in order from the object side. (A configuration in which a negative lens 7d is added to the image plane side of the second lens group 2 in the first embodiment). The fifth lens group 10 includes a first positive lens 10a, a second positive lens 10b, and a negative lens 1 arranged in order from the object side.
0c (the first lens).
Configuration in which the arrangement order of each lens of the fifth lens group 5 in the embodiment is reversed).

In the zoom lens according to the present embodiment,
By moving the third lens group 8 perpendicular to the optical axis,
The image fluctuation at the time of camera shake is corrected. When the paraxial lateral magnification of the third lens group 8 is β3, the paraxial lateral magnification of the fourth lens group 9 is β4, and the paraxial lateral magnification of the fifth lens group 10 is β5, the following (Equation 8) is obtained. The condition is satisfied. [Equation 8] 1.5 <(1−β3) · β4 · β5 <2.5 The following (Table 2) shows specific numerical examples of the zoom lens according to the present embodiment. [Table 2] f = 5.74 to 54.5 F / 2.01 to F / 2.68 r 1 33.320 d 1 1.000 n 1 1.84666 ν 1 23.8 r 2 19.505 d 2 4.950 n 2 1.60311 ν 2 60.6 r 3 542.028 d 3 0.120 r 4 23.698 d 4 2.850 n 3 1.62041 ν 3 60.3 r 5 111.910 d 5 Variable r 6 26.931 d 6 0.650 n 4 1.80420 ν 4 46.6 r 7 7.534 d 7 2.498 r 8 −17.589 d 8 0.600 n 5 1.72916 ν 5 54.7 r 9 9.074 d 9 2.600 n 6 1.84666 ν 6 23.8 r10 −398.060 d10 0.833 r11 −10.348 d11 0.650 n 7 1.69680 ν 7 55.6 r12 −26.667 d12 Variable r13 Aperture d13 1.07 r14 20.596 d14 2.600 n 8 1.60602 ν 8 57.5 r15 −20.416 d15 0.120 r16 32.867 d16 2.600 n 9 1.69680 ν 9 55.6 r17 −9.566 d17 0.600 n10 1.84666 ν10 23.8 r18 −23.839 d18 Variable r19 −22.741 d19 1.850 n11 1.80518 ν11 25.4 r20 −9.814 d20 0.700 n12 1.72916 ν12 54.7 r21 17.534 d21 Variable r22 1409.039 d11 2.550 n 60.6 r23 −11.646 d23 0.120 r24 14.605 d24 3.300 n14 1.56883 ν14 56.1 r25 −10.003 d25 0.600 n15 1.84666 ν15 23.8 r26−318.848 d26 4.000 r27 ∞ d27 3.300 n16 1.51633 ν16 64.2 r28 可 変 Variable interval: fd 5 d12 d18 d21 5.74 0.716 17.755 1.079 9.000 26.9 13.015 5.457 4.809 5.270 54.5 17.521 0.950 1.079 9.000 Surface 14 aspheric coefficient K −0.333 A −8.00 250 × 10 ^-3 B −1.24440 × 10 ^-4 C 9.17124 × 10 ^-6 D -1.75819 × 10 ^-7 The meanings of the respective symbols in the above (Table 2) are the same as those in the above (Table 1).

In the zoom lens having the specifications shown in Table 2 above, the shift sensitivity of the third lens group 8 in the direction perpendicular to the optical axis is defined by (1−β3) · β4 · β5 = 1.68. , (5) is satisfied. Further, the Abbe number ν31 of the second positive lens 8b and the Abbe number ν of the negative lens 8c that constitute the cemented lens of the third lens group 8
The difference (ν31−ν32) from 32 is 31.8, which satisfies the condition of (Equation 6).

FIGS. 7 to 9 show the wide-angle end (wide end), intermediate position (normal position),
Aberration performance diagram at rest at the telephoto end (telephoto end) is shown.
FIG. 10 shows an aberration performance chart at the telephoto end when correcting by 0.5 °. The meanings of the respective symbols in FIGS. 7 to 10 are the same as those in FIGS. 2 to 5.

As is apparent from these aberration performance diagrams (FIGS. 7 to 10), it is understood that the zoom lens according to the present embodiment can realize good optical performance with small aberration.

[0029]

As described above, according to the present invention,
Since the camera shake correction is performed by moving the third lens group having a small diameter in a direction perpendicular to the optical axis, it is advantageous for miniaturization as compared with the type in which the camera shake correction is performed by mounting a variable vertex angle prism. . In addition, since the amount of movement of the third lens group during camera shake correction can be reduced, deterioration in optical performance during camera shake can be reduced, and fluctuations in the peripheral light amount can be suppressed. As a result, a high-performance and compact zoom lens can be realized.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a configuration of a zoom lens according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating aberration performance of the zoom lens according to the first embodiment of the present invention at the wide-angle end when the zoom lens is stationary.

FIG. 3 is an aberration performance diagram when the zoom lens according to the first embodiment of the present invention is stationary at an intermediate position.

FIG. 4 is an aberration performance diagram of the zoom lens according to the first embodiment of the present invention at the telephoto end when the zoom lens is stationary.

FIG. 5 is an aberration performance diagram at the telephoto end of the zoom lens according to the first embodiment of the present invention at the time of 0.5 ° correction.

FIG. 6 is a layout diagram showing a configuration of a zoom lens according to a second embodiment of the present invention.

FIG. 7 is an aberration performance diagram of the zoom lens according to the second embodiment of the present invention at the wide-angle end at rest.

FIG. 8 is a diagram showing aberration performance when the zoom lens according to the second embodiment of the present invention is stationary at an intermediate position.

FIG. 9 is a diagram showing aberration performance when the zoom lens according to the second embodiment of the present invention is stationary at the telephoto end.

FIG. 10 is an aberration performance diagram at the telephoto end of a zoom lens according to a second embodiment of the present invention at the time of 0.5 ° correction.

[Explanation of symbols]

1, 6 1st lens group 2, 7 2nd lens group 3, 8 3rd lens group 4, 9 4th lens group 5, 10 5th lens group S stop EG Optical such as cover glass or low-pass filter of image sensor Flat glass equivalent to

Continued on the front page F term (reference) 2H087 KA03 MA14 NA07 PA09 PA10 PA16 PB14 PB15 QA02 QA06 QA07 QA17 QA21 QA25 QA32 QA34 QA41 QA46 RA05 RA12 RA42 SA43 SA47 SA49 SA53 SA55 SA63 SA65 SA72 SA74 SA76 SB04 SB14 SB14 SB24

Claims (3)

[Claims] 1. A fixed first lens group having a positive refractive power and arranged in order from an object side to an image plane side;
A second lens group having a negative refractive power and performing a zooming action by moving on the optical axis, a third lens group having a positive refractive power and fixed with respect to the image plane, Has a refractive power of
A fourth lens group moving on the optical axis so as to keep an image plane, which fluctuates due to zooming or a change in object distance, at a fixed position from the reference plane, and a fifth lens group having a positive refractive power and fixed Wherein the movement of the third lens group perpendicular to the optical axis corrects image fluctuations during camera shake, and the paraxial lateral magnification of the third lens group is β3. When the paraxial lateral magnification of the fourth lens group is β4 and the paraxial lateral magnification of the fifth lens group is β5, the following condition (Equation 1) is satisfied. [Equation 1] 1.5 <(1−β3) · β4 · β5 <2.5 2. The zoom lens according to claim 1, wherein the third group of lenses includes a cemented lens of one positive lens and one negative lens. 3. The Abbe number of the positive lens constituting the cemented lens is ν31, and the Abbe number of the negative lens is ν32.
Wherein the following condition (Equation 2) is satisfied:
A zoom lens according to claim 1. [Equation 2] ν31−ν32> 25