JP2011137875A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact zoom lens that has a high variable power ratio and can obtain a high optical performance. <P>SOLUTION: The zoom lens includes: a first lens group L1 having a positive refractive power; a second lens group L2 having a negative refractive power; a third lens group L3 having a positive refractive power; and a fourth lens group L4 having a positive refractive power. A stop SP is disposed between the second lens group L2 and the third lens group L3. The first lens group L1 has: a negative lens 1; a positive lens 2; and two positive lenses 3 and 4, each having a convex surface on an object side. The second lens group L2 has: at least three negative lenses 5, 6, and 8; and a positive lens 7. The third lens group L3 includes: a positive lens 9 having a convex surface on the object side; and a negative meniscus lens 10 having a concave surface on an image surface side. The zoom lens satisfies the following equations: 1.4<¾f<SB>2</SB>¾/f<SB>W</SB><2.0; and 0.3<f<SB>1</SB>/f<SB>T</SB><0.6; wherein a combined focal length of the first lens group L1 is f<SB>1</SB>, a combined focal length of the second lens group L2 is f<SB>2</SB>, a focal length of the entire system at a wide angle end is f<SB>W</SB>, and a focal length of the entire system at a telephoto end is f<SB>T</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a zoom lens and an imaging apparatus.

  In recent years, surveillance cameras using solid-state imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-oxide Semiconductor) sensors, and imaging devices such as video cameras and digital cameras have become more sophisticated and smaller. . Accordingly, high optical performance and downsizing are also required for zoom lenses (photographing optical systems) used in these imaging apparatuses.

  As a zoom lens used in such an imaging apparatus, in order from the object side, a first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power as a whole, and a whole as a whole A third lens group having a positive refractive power and a fourth lens group having a positive refractive power as a whole, and performing a zooming operation (zooming) by displacing the second lens group in the optical axis direction; There is known a so-called rear focus type zoom lens that corrects an image plane variation accompanying zooming and performs a focusing operation (focusing) by displacing the fourth lens group in the optical axis direction (for example, See Patent Documents 1 to 5.)

  In this rear focus type zoom lens, the effective diameter of the first lens group can be reduced compared to a zoom lens that performs focusing by displacing the first lens group in the optical axis direction, and the entire lens system is easy. Can be reduced in size. Further, close-up photography is possible, and a relatively small and light lens group is displaced in the optical axis direction, so that focusing can be performed quickly with a small driving force.

  By the way, with the miniaturization of pixels due to the miniaturization and the increase in the number of pixels described above, there is a demand for a compact zoom lens having high optical performance and a short overall lens length. However, in order to obtain high optical performance, it is necessary to increase the number of lenses and lengthen the total length of the lenses, which makes it difficult to reduce the size.

  In addition, in a conventional zoom lens, if an attempt is made to maintain a small size while increasing a zoom ratio, aberration fluctuations accompanying zooming increase, making it difficult to obtain good optical performance from the wide-angle end to the telephoto end. . In particular, in a zoom lens with a high zoom ratio, it is difficult to correct spherical aberration at the telephoto end. Further, with the miniaturization and high zoom ratio, there is a problem of increasing the amount of aberration generated by the movable lens group.

JP 2007-171248 A JP 2007-066534 A JP 2005-345507 A JP-A-2005-024844 JP 2004-325566 A

  The present invention has been proposed in view of such a conventional situation, and has a high zoom ratio and high optical performance while having a high zoom ratio, and an imaging device including such a zoom lens. An object is to provide an apparatus.

In order to achieve the above object, a zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power as a whole, and a whole. A third lens group having a positive refractive power and a fourth lens group having a positive refractive power as a whole, and performing a zooming operation by displacing the second lens group in the optical axis direction, 4 is a zoom lens that corrects an image plane variation caused by zooming by displacing the lens group 4 in the optical axis direction and performs a focusing operation between the second lens group and the third lens group. An aperture is disposed, and the first lens group includes, in order from the object side, a negative lens, a positive lens, and two positive lenses having a convex surface on the object side. In order from the side, at least three negative lenses and a positive lens The third lens group includes, in order from the object side, a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side, and the combined focal length of the first lens group F ₁ [mm], the combined focal length of the second lens group is f ₂ [mm], the focal length of the entire system at the wide-angle end is f _W [mm], and the focal length of the entire system at the telephoto end is f _T [mm ], The following relationship is satisfied: 1.4 <| f ₂ | / f _W <2.0, 0.3 <f ₁ / f _T <0.6.

  As described above, according to the present invention, a small zoom lens that has a high zoom ratio (specifically, 15 times or more) and can obtain high optical performance, and an imaging device including such a zoom lens. An apparatus can be provided.

It is a block diagram which shows an example of the zoom lens to which this invention is applied. 1 is a configuration diagram of a zoom lens shown in Embodiment 1. FIG. FIG. 4 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a magnification chromatic aberration diagram at the wide-angle end of the zoom lens shown in Example 1. FIG. FIG. 3 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the intermediate focal position of the zoom lens shown in Example 1. FIG. FIG. 4 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 1. FIG. FIG. 6 is a configuration diagram of a zoom lens shown in Example 2. FIG. 6 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the wide-angle end of the zoom lens shown in Example 2. FIG. 6 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the intermediate focal position of the zoom lens shown in Example 2. FIG. 7 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 2. FIG. 6 is a configuration diagram of a zoom lens shown in Example 3. FIG. 6 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the wide-angle end of the zoom lens shown in Example 3. FIG. 6 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a lateral chromatic aberration diagram at an intermediate focal position of the zoom lens shown in Example 3. FIG. 7 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 3. 6 is a configuration diagram of a zoom lens shown in Example 4. FIG. FIG. 9 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the wide angle end of the zoom lens shown in Example 4. FIG. 8 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the intermediate focal position of the zoom lens shown in Example 4. FIG. 7 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 4. FIG. 6 is a configuration diagram of a zoom lens shown in Example 5. FIG. 9 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the wide angle end of the zoom lens shown in Example 5. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the intermediate focal position of the zoom lens shown in Example 5. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 5. FIG. 10 is a configuration diagram of a zoom lens shown in Example 6. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the wide angle end of the zoom lens shown in Example 6. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the intermediate focal position of the zoom lens shown in Example 6. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a chromatic aberration diagram of magnification at the telephoto end of the zoom lens shown in Example 6.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that the lens data and the like exemplified in the following description are merely examples, and the present invention is not necessarily limited thereto, and can be appropriately modified and implemented without changing the gist thereof.

  A zoom lens to which the present invention is applied is used as an imaging optical system of an imaging apparatus such as a surveillance camera, a digital video camera, or a digital still camera as shown in FIG. A first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power as a whole, a third lens unit L3 having a positive refractive power as a whole, and a positive refractive power as a whole And a fourth lens unit L4. A stop SP is disposed between the second lens unit L2 and the third lens unit L3, and corresponds to an optical filter, a face plate, or the like between the fourth lens unit L4 and the image plane IP. An optical block G is arranged.

  In this zoom lens, a zooming operation (zooming) is performed on the fixed first and third lens groups L1 and L3 by displacing the second lens group L2 in the optical axis direction. A focusing operation (focusing) is performed by displacing the lens unit L4 in the optical axis direction. Further, in this zoom lens, during zooming from the wide-angle end to the telephoto end, the second lens unit L2 is moved toward the image plane side in the direction of arrow a in FIG. 1, and at the same time, the second lens group L2 is moved in the directions of arrows b and c in FIG. By moving the four lens unit L4 so as to draw a locus that is convex toward the object side, the image plane variation accompanying zooming is corrected.

  Note that an arrow b indicated by a solid line and an arrow c indicated by a broken line in FIG. 1 indicate movement trajectories for correcting image plane fluctuations accompanying zooming when focusing on an object at infinity and an object at close distance, respectively. Indicates. Thus, by moving the fourth lens unit L4 so as to draw a locus that is convex toward the object side, the space between the third lens unit L3 and the fourth lens unit L4 is effectively used, and the zoom lens It becomes possible to shorten the total length of the.

  The imaging device is a solid-state imaging device (such as a CCD (Charge Coupled Device) or CMOS (Complementary Mental-Oxide Semiconductor device) sensor) in which light incident from the object side of the zoom lens is finally disposed on the image plane IP. An image is formed on the imaging surface of the photoelectric conversion element. The imaging device photoelectrically converts the light received by the solid-state imaging device and outputs it as an electrical signal to generate a digital image corresponding to the image of the subject, for example, an HDD (Hard Disk Drive), a memory card, an optical disk, etc. Recording is performed on a recording medium such as a magnetic tape. When the imaging device is a silver salt film camera, the image plane IP corresponds to the film plane.

  Among the lens groups L1 to L4 constituting the zoom lens to which the present invention is applied, the first lens unit L1 includes, in order from the object side, a negative lens 1, a positive lens 2, and two objects having a convex surface on the object side. Positive lenses 3 and 4. This makes it easy to correct the spherical aberration at the telephoto end while dispersing the positive refractive power of the first lens unit L1 to each lens.

  The second lens unit L2 includes at least three negative lenses 5, 6, and 7 and a positive lens 8 in order from the object side. As a result, it is possible to suppress distortion at the wide-angle end and correct variations in spherical aberration due to zooming.

  The third lens unit L3 includes, in order from the object side, a positive lens 9 having a convex surface on the object side and a negative meniscus lens 10 having a concave surface on the image side. Accordingly, the principal point position of the third lens unit L3 is moved to the object side, the actual distance interval between the third lens unit L3 and the fourth lens unit L4 is shortened, and the zoom lens as a whole is further reduced in size. Yes.

  The fourth lens unit L4 includes, in order from the object side, a positive lens 11 in which at least one surface is aspherical and both surfaces are convex, and a negative meniscus lens 12 in which the object side is concave. Thereby, it is possible to reduce aberration fluctuations during focusing.

In the zoom lens to which the present invention is applied, the combined focal length of the first lens unit L is f ₁ [mm], the combined focal length of the second lens unit L2 is f ₂ [mm], and the focal length of the entire system at the wide angle end is set. It is preferable that the following relations (1) and (2) are satisfied, where f _W [mm] and the focal length of the entire system at the telephoto end are f _T [mm].
1.4 <| f ₂ | / f _W <2.0 (1)
0.3 <f ₁ / f _T <0.6 (2)

  In the present invention, below the lower limit of the above formula (1), it is difficult to correct aberration variation satisfactorily from the wide-angle end to the telephoto end during zooming. On the other hand, when the value exceeds the upper limit of the above formula (1), the amount of movement from the wide-angle end to the telephoto end at the time of zooming increases, so the total length of the zoom lens becomes long.

  In the present invention, if the lower limit of the above formula (2) is not reached, it is difficult to satisfactorily correct spherical aberration at the telephoto end. On the other hand, when the value exceeds the upper limit of the above formula (2), the focal length of the first lens unit L1 increases, the effect of downsizing is reduced, and the overall length of the zoom lens is increased.

In the present invention, it is more preferable to satisfy the following relationships (1) ′ and (2) ′.
1.45 <| f ₂ | / f _W <1.7 (1) ′
0.32 <f ₁ / f _T <0.55 (2) ′

In the zoom lens to which the present invention is applied, when the length on the optical axis from the apex on the object side of the lens 1 located closest to the object side of the first lens unit L1 to the image plane is Σ _D [mm] It is preferable that the relationship of the following formula (3) is satisfied.
_{0.6 <(Σ D / f T} ) <1.3 ... (3)

  In the present invention, if the total length of the zoom lens is shortened beyond the lower limit of the above formula (3), it becomes difficult to correct field curvature. On the other hand, if the upper limit value of the above equation (3) is exceeded, aberration correction is easy, but the total length of the zoom lens becomes long.

In the present invention, it is more preferable to satisfy the following relationship (3) ′.
0.8 <(Σ _D / f _T ) <1.2 (3) ′

In the zoom lens to which the present invention is applied, it is preferable that the relationship of the following formula (4) is satisfied when the Abbe number of the positive lens 1 located closest to the object side in the first lens unit L1 is ν _1D .
80 <ν _1D (4)

  In the present invention, below the lower limit of the above formula (4), it is difficult to satisfactorily correct axial chromatic aberration and lateral chromatic aberration at the telephoto end.

  The third lens unit L1 includes, in order from the object side, a positive lens 9 having at least one aspheric surface and a convex surface on the object side, and a negative meniscus lens 10 having a concave surface on the image side. It is preferable. Thereby, correction of spherical aberration and coma aberration can be facilitated.

Furthermore, in the present invention, when the radius of curvature of the lens surface on the object side of the meniscus lens 10 is R _3W [mm] and the radius of curvature of the lens surface on the image side is R _3T [mm], the following formula (5 ) Is preferably satisfied.
1.5 <R _3W / R _3T <3.0 (5)

  In the present invention, when the value falls below the lower limit of the above formula (5), the principal point position of the third lens unit L3 described above is moved to the object side, and the actual distance interval between the third lens unit L3 and the fourth lens unit L4. This shortens the effect of reducing the overall size of the zoom lens and reduces the overall length of the zoom lens. On the other hand, if the upper limit value of the above equation (5) is exceeded, the actual distance interval between the third lens unit L3 and the fourth lens unit L4 becomes too short, and a sufficient moving space for the fourth lens unit L4 is ensured. It becomes difficult.

In the present invention, it is more preferable to satisfy the following relationship (5) ′.
2.0 <R _3W / R _3T <2.5 (5) ′

In the zoom lens to which the present invention is applied, it is preferable that the relationship of the following formula (6) is satisfied when the focal length of the third lens unit L3 is f ₃ [mm].
4.0 <f ₃ / f _W <6.0 (6)

  In the present invention, when the value falls below the lower limit of the above formula (6), the positive refractive power of the third lens unit L3 becomes strong, and spherical aberration, coma aberration, and astigmatism are greatly generated. It will be difficult to correct it. On the other hand, when the value exceeds the upper limit of the above formula (6), the positive refractive power of the third lens unit L3 becomes weak, and the positive refractive power of the fourth lens unit L must be increased. In this case, it is difficult to satisfactorily correct spherical aberration, coma, astigmatism, and distortion.

In the present invention, it is more preferable to satisfy the following relationship (6) ′.
4.5 <f ₃ / f _W <5.5 (6) ′

In the present invention, it is preferable that the fourth lens unit L4 satisfies the relationship of the following formula (7) when the lateral magnification when focusing on an object at infinity at the telephoto end is β _4T. .
0.3 <β _4T <0.6 (7)

  In the present invention, when the value falls below the lower limit of the above formula (7), the back focus becomes long, and the zoom lens becomes large. On the other hand, when the value exceeds the upper limit of the above formula (7), the amount of extension of the fourth lens unit L4 increases, and the actual distance between the third lens unit L3 and the fourth lens unit L4 cannot be shortened. Therefore, it is difficult to reduce the size of the zoom lens.

In the present invention, it is more preferable to satisfy the following relationship (7) ′.
0.35 <β _4T <0.55 (7) ′

  In a zoom lens to which the present invention that satisfies the above conditions is applied, while having a high zoom ratio (specifically, about 15 to 25 times), distortion at the wide-angle end, spherical aberration at the telephoto end, It is possible to easily correct fluctuations in spherical aberration associated with zooming, to obtain good optical performance from the wide-angle end to the telephoto end, and to further reduce the size by shortening the overall length. .

  Since this zoom lens is sufficiently compatible with a small solid-state imaging device with a large number of pixels, it is small when applied to an imaging optical system of an imaging device such as a surveillance camera, a digital video camera, or a digital still camera. Thus, an imaging device having high optical performance can be realized.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

(Example 1)
The configuration of the zoom lens based on the design data of Example 1 is shown in FIG. The zoom lens of Example 1 shown in FIG. 2 has the same configuration as the zoom lens shown in FIG. 1, and the design data of this zoom lens is as shown in Table 1 below.

The surface number “i” (i represents a natural number) shown in Table 1 indicates that the lens surface of the lens closest to the object side among the lenses constituting the zoom lens is the first lens surface, and is on the image surface side. The number of the lens surface which increases sequentially as it goes is shown.
Further, among the lenses “GjRk (j is a natural number, k represents 1 or 2)” shown in Table 1, G is a lens that is located closest to the object among the lenses that constitute the zoom lens. As the second, the numbers of the lenses that sequentially increase toward the image plane side are shown. On the other hand, R indicates that the lens surface on the object side of each lens is 1, and the lens surface on the image plane side is 2. “Aperture” and “optical block (plane)” are also described together.
In addition, “R” shown in Table 1 is the curvature radius [mm] of the lens surface corresponding to each surface number (however, a surface where the value of R is ∞ indicates that the surface is a plane). Is shown.
“D” shown in Table 1 indicates an axial upper surface distance [mm] between the i-th lens surface and the i + 1-th lens surface from the object side, and when variable, the wide-angle end, the intermediate focal position, The axial upper surface distance [mm] at the telephoto end is shown. Note that “focal length” and “F number” at the wide-angle end, the intermediate focal position, and the telephoto end are also described together.
Further, “Nd” shown in Table 1 indicates the refractive index of each lens.
Further, “Vd” shown in Table 1 indicates the Abbe number of each lens.
Table 1 shows (1) “| f ₂ | / f _W ”, (2) “f ₁ / f _T ”, (3) “Σ _D / f _T ”, (4) “ν _1D ”, (5) Conditional expressions of “R _3W / R _3T ”, (6) “f ₃ / f _W ”, and (7) “β _4T ” are shown.
Table 1 shows the surface numbers of the aspherical lenses and their aspherical coefficients. The aspheric surface can be represented by the following aspheric expression x.

  FIG. 3, FIG. 4 and FIG. 5 show spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, and lateral chromatic aberration diagrams by the zoom lens of Example 1 configured as described above.

3 shows various aberrations at the wide-angle end, FIG. 4 shows various aberrations at the intermediate focal position, and FIG. 5 shows various aberrations at the telephoto end.
In the spherical aberration diagram, the spherical aberration at the d-line is indicated by a solid line, and the spherical aberration at the g-line is indicated by a one-dot chain line.
The astigmatism diagram shows astigmatism with respect to sagittal ray ΔS and median ray ΔM at each wavelength.
The distortion diagram shows distortion at a wavelength of 587.56 nm.
The lateral chromatic aberration diagram shows the chromatic aberration at the g-line.

  As shown in Table 1, the zoom lens of Example 1 satisfies the above-described conditions of the present invention. In the zoom lens of Example 1, each aberration is satisfactorily corrected as shown in FIGS. 3, 4 and 5 while having a zoom ratio of about 17.9 times. Recognize.

(Example 2)
The configuration of the zoom lens based on the design data of Example 2 is shown in FIG. The zoom lens of Example 2 shown in FIG. 6 has the same configuration as the zoom lens shown in FIG. 1. The design data of the zoom lens shown in Example 2 is as shown in Table 2 below. is there. The notation method in Table 2 is the same as in Table 1.

  FIGS. 7, 8 and 9 show spherical aberration diagrams, astigmatism diagrams, distortion aberration diagrams, and magnification chromatic aberration diagrams of the zoom lens according to the second embodiment configured as described above. In addition, about the description method of FIGS. 7-9, it is the same as that of the case of FIGS.

  As shown in Table 2, the zoom lens of Example 2 satisfies the above-described conditions of the present invention. In the zoom lens of Example 2, each aberration is well corrected as shown in FIGS. 7, 8 and 9 while having a zoom ratio of about 18.8. Recognize.

(Example 3)
The configuration of the zoom lens based on the design data of Example 3 is shown in FIG. The zoom lens of Example 3 shown in FIG. 10 has the same configuration as the zoom lens shown in FIG. 1. The design data of the zoom lens shown in Example 3 is as shown in Table 3 below. is there. The notation method in Table 3 is the same as in Table 1.

  FIG. 11, FIG. 12 and FIG. 13 show spherical aberration diagrams, astigmatism diagrams, distortion diagrams, and lateral chromatic aberration diagrams by the zoom lens of Example 3 configured as described above. In addition, about the description method of FIGS. 11-13, it is the same as that of the case of FIGS.

  As shown in Table 3, the zoom lens of Example 3 satisfies the above-described conditions of the present invention. In the zoom lens of Example 3, each aberration is satisfactorily corrected as shown in FIGS. 11, 12 and 13 while having a zoom ratio of about 19.0 times. Recognize.

Example 4
The configuration of the zoom lens based on the design data of Example 4 is shown in FIG. The zoom lens of Example 4 shown in FIG. 14 has the same configuration as the zoom lens shown in FIG. 1, and the design data of the zoom lens shown in Example 4 is as shown in Table 4 below. is there. The notation method in Table 4 is the same as in Table 1.

  FIGS. 15, 16, and 17 show spherical aberration diagrams, astigmatism diagrams, distortion diagrams, and lateral chromatic aberration diagrams of the zoom lens according to Example 4 configured as described above. In addition, about the description method of FIGS. 15-17, it is the same as that of the case of FIGS.

  As shown in Table 4, the zoom lens of Example 4 satisfies the above-described conditions of the present invention. In the zoom lens of Example 4, each aberration is satisfactorily corrected as shown in FIGS. 15, 16, and 17 while having a zoom ratio of about 17.2. Recognize.

(Example 5)
The configuration of the zoom lens based on the design data of Example 5 is shown in FIG. The zoom lens of Example 5 shown in FIG. 18 has the same configuration as the zoom lens shown in FIG. 1. The design data of the zoom lens shown in Example 5 is as shown in Table 5 below. is there. The notation method in Table 5 is the same as in Table 1.

  FIG. 19, FIG. 20 and FIG. 21 show spherical aberration diagrams, astigmatism diagrams, distortion diagrams, and magnification chromatic aberration diagrams by the zoom lens of Example 5 configured as described above. In addition, about the description method of FIGS. 19-21, it is the same as that of the case of FIGS.

  As shown in Table 5, the zoom lens of Example 5 satisfies the above-described conditions of the present invention. In the zoom lens of Example 5, each aberration is well corrected as shown in FIGS. 19, 20, and 21 while having a zoom ratio of about 16.5 times. Recognize.

(Example 6)
The configuration of the zoom lens based on the design data of Example 6 is shown in FIG. The zoom lens of Example 6 shown in FIG. 22 has the same configuration as the zoom lens shown in FIG. 1. The design data of the zoom lens shown in Example 6 is as shown in Table 6 below. is there. The notation method in Table 6 is the same as in Table 1.

  FIG. 23, FIG. 24, and FIG. 25 show spherical aberration diagrams, astigmatism diagrams, distortion diagrams, and magnification chromatic aberration diagrams by the zoom lens of Example 6 configured as described above. In addition, about the description method of FIGS. 23-25, it is the same as that of the case of FIGS.

  As shown in Table 6, the zoom lens of Example 6 satisfies the above-described conditions of the present invention. In the zoom lens of Example 6, each aberration is satisfactorily corrected as shown in FIGS. 23, 24 and 25 while having a zoom ratio of about 24.7. Recognize.

  L1 ... 1st lens group L2 ... 2nd lens group L3 ... 3rd lens group L4 ... 4th lens group SP ... Diaphragm G ... Optical block IP ... Image plane

Claims (7)

In order from the object side, a first lens group having a positive refractive power as a whole, a second lens group having a negative refractive power as a whole, a third lens group having a positive refractive power as a whole, and a positive as a whole A fourth lens group having a refractive power of ## EQU2 ## to perform a magnification operation by displacing the second lens group in the optical axis direction, and to change a magnification by displacing the fourth lens group in the optical axis direction. A zoom lens that corrects the accompanying image plane variation and performs a focusing operation,
A diaphragm is disposed between the second lens group and the third lens group,
The first lens group includes, in order from the object side, a negative lens, a positive lens, and two positive lenses having a convex surface on the object side,
The second lens group includes at least three negative lenses and a positive lens in order from the object side,
The third lens group includes, in order from the object side, a positive lens having a convex surface on the object side and a negative meniscus lens having a concave surface on the image side.
The combined focal length of the first lens group is f ₁ [mm], the combined focal length of the second lens group is f ₂ [mm], the focal length of the entire system at the wide angle end is f _W [mm], and at the telephoto end. When the focal length of the entire system is f _T [mm],
1.4 <| f ₂ | / f _W <2.0,
0.3 <f ₁ / f _T <0.6
A zoom lens characterized by satisfying the above relationship. When the length on the optical axis from the apex on the object side to the image plane of the lens located closest to the object side in the first lens group is Σ _D [mm]
0.6 <(Σ _D / f _T ) <1.3
The zoom lens according to claim 1, wherein the following relationship is satisfied. When the Abbe number of the positive lens located closest to the object side in the first lens group is ν _1D ,
80 <ν _1D
The zoom lens according to claim 1, wherein the zoom lens satisfies the following relationship. The third lens group includes, in order from the object side, a positive lens in which at least one surface is aspherical and the object side is convex, and a negative meniscus lens in which the image side is concave.
When the radius of curvature of the lens surface on the object side of the meniscus lens is R _3W [mm] and the radius of curvature of the lens surface on the image plane side is R _3T [mm],
1.5 <R _3W / R _3T <3.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the following relationship. When the focal length of the third lens group is f ₃ [mm],
4.0 <f ₃ / f _W <6.0
The zoom lens according to claim 1, wherein the following relationship is satisfied. When the lateral magnification when the fourth lens group is focused on an object at infinity at the telephoto end is β _4T ,
0.3 <β _4T <0.6
The zoom lens according to claim 1, wherein the following relationship is satisfied. The zoom lens according to any one of claims 1 to 6,
An image pickup apparatus comprising: a solid-state image pickup device that picks up an image formed by the zoom lens.

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