JP2008151832A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which is thin in an optical axis direction, and has a wide viewing angle and a high variable power ratio, and further whose aberration is satisfactorily corrected. <P>SOLUTION: The zoom lens comprises a first lens group having negative refractive power, a second lens group having positive refractive power and a third lens group having positive refractive power in order from an object side, and varies power by changing space between the respective lens groups when varying power from a wide angle end to a telephoto end. In the zoom lens, the first lens group has at least one negative lens, and satisfies conditional expressions 1.9<n<SB>1n</SB>and 35<ν<SB>1n</SB>. Provided that n<SB>1n</SB>: refractive index of the negative lens, and ν<SB>1n</SB>: Abbe number of the negative lens. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a zoom lens, which is used in a digital camera, a video camera, etc., has a zoom ratio of about 3 times, an angle of view at the wide angle end of 60 ° or more, particularly a thin and compact thickness in the optical axis direction, The present invention relates to a zoom lens suitable for an imaging device such as a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor).

In recent years, many digital still cameras, video cameras, and the like using CCDs and CMOSs have been used, but the demand for particularly thin cameras is increasing. There is disclosed a zoom lens for CCD having negative and positive power arrangement that is often used for this type of camera (see Patent Documents 1 and 2).
JP 2006-227040 A JP 2002-372667 A

  However, in the above patent document, the spherical lens uses a conventional glass material for polishing glass, and there is a limit to miniaturization and high performance of the lens within the limited refractive index and chromatic dispersion range. .

  The present invention has been made in view of such problems. By using a translucent ceramic having a refractive index higher than that of glass or having a small chromatic dispersion, the thickness in the optical axis direction is thin, a wide angle of view, and a high variation. An object of the present invention is to propose a zoom lens having a magnification ratio and various aberrations corrected satisfactorily.

The object is achieved by the invention described below.
1. In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The zoom lens according to claim 1, wherein the first lens group includes at least one negative lens and satisfies the following conditional expression.

1.9 <n _1n (1)
35 <ν _1n (2)
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens 2. The zoom lens according to 1, wherein the negative lens satisfies the following conditional expression.

2.0 <n _1n (3)
40 ≦ ν _1n (4)
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The zoom lens according to claim 1, wherein the first lens group includes at least one negative lens and satisfies the following conditional expression.

1.8 <n _1n (5)
50 <ν _1n (6)
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens The zoom lens according to any one of 1 to 3, wherein the negative lens uses translucent ceramics.
5. The zoom lens according to any one of claims 1 to 4, wherein the negative lens is a composite aspherical lens in which an aspherical resin layer is formed on a spherical lens made of translucent ceramics.
6). The zoom lens according to any one of 1 to 5, wherein the first lens group satisfies the following conditional expression.

−1.5 <f ₁ / f _T <−0.5 (7)
However,
f ₁ : focal length of the first lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to any one of 1 to 5, wherein the first lens group satisfies the following conditional expression.

−1.1 <f ₁ / f _T <−0.7 (8)
However,
f ₁ : focal length of the first lens group f _T : focal length of the entire system at the telephoto end In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The second lens group has at least one positive lens, and satisfies the following conditional expression:

1.9 <n _2p (9)
35 <ν _2p (10)
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens 9. The zoom lens according to 8, wherein the positive lens satisfies the following conditional expression.

2.0 <n _2p (11)
40 ≦ ν _2p (12)
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The second lens group has at least one positive lens, and satisfies the following conditional expression:

1.8 <n _2p (13)
50 <ν _2p (14)
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens The zoom lens according to any one of 8 to 10, wherein the positive lens uses translucent ceramics.
12 The zoom lens according to any one of 8 to 11, wherein the second lens group satisfies the following conditional expression.

0.3 <f ₂ / f _T <0.9 (15)
However,
f ₂ : focal length of the second lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to any one of 8 to 11, wherein the second lens group satisfies the following conditional expression.

0.4 <f ₂ / f _T <0.8 (16)
However,
f ₂ : focal length of the second lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to any one of 1 to 13, wherein the second lens group includes a three-piece cemented lens including a positive lens, a negative lens, and a positive lens in order from the object side.
15. The zoom lens according to any one of 1 to 14, wherein the third lens group includes one positive lens made of plastic and satisfies the following conditional expression.

0.5 <f _T / f ₃ <1.5 (17)
However,
f _T : focal length of the entire system at the telephoto end f ₃ : focal length of the third lens group The zoom lens according to any one of 1 to 14, wherein the third lens group includes one positive lens made of plastic and satisfies the following conditional expression.

0.8 <f _T / f ₃ <1.2 (18)
However,
f _T : focal length of the entire system at the telephoto end f ₃ : focal length of the third lens group The zoom lens according to any one of 1 to 16, wherein the zoom lens moves at least the third lens group to perform focusing from infinity to a finite distance.
18. The zoom lens according to any one of 1 to 17, wherein the zoom lens satisfies the following conditional expression.

1.0 <SD / 2Y <2.0 (19)
However,
SD: Sum of axial thickness of each lens group 2Y: Diagonal length of image pickup device 19. The zoom lens according to any one of 1 to 17, wherein the zoom lens satisfies the following conditional expression.

1.2 <SD / 2Y <1.7 (20)
However,
SD: Sum of axial thickness of each lens group 2Y: Diagonal length of image sensor

  According to the zoom lens of the present invention, by using a translucent ceramic having a refractive index higher than that of glass or having a small chromatic dispersion, the thickness in the optical axis direction is reduced, and a wide angle of view and a high zoom ratio are obtained. As a result, the various aberrations are favorably corrected.

  First, a basic configuration of the zoom lens according to the present invention will be described.

  The lens type of the zoom lens according to the present invention has a negative refractive power in the first lens group and a positive refractive power in the second lens group. A sufficient back focus is obtained for arranging a filter, a cover glass, etc., and when the aperture stop is arranged behind the negative first lens group, a large peripheral light quantity ratio can be obtained due to the divergent effect of the negative lens group. There is an advantage. Since the third lens group has a positive refractive power, a sufficient telecentricity can be ensured, which is particularly effective when the imaging element is a CCD. In order to achieve both compactness and telecentricity, an aperture stop may be provided on the object side of the second lens group. If the infrared cut filter is a reflective type with a low pass filter surface coated, it is not necessary to insert an absorption type infrared cut filter glass separately, so the thickness in the optical axis direction can be reduced. It becomes possible to set it as the structure advantageous to compactness.

  Since the translucent ceramics used in this embodiment have a relatively large Abbe number, the first lens group having a negative refractive power is a negative lens, and the second lens group having a positive refractive power is a positive lens. It is preferable to apply to. Combining this lens with a positive lens having a small Abbe number in the first lens group and a negative lens having a small Abbe number in the second lens group can achieve good chromatic aberration correction. Further, since the refractive index is high, even if the lens has the same refractive power, the radius of curvature can be increased, so that various aberrations occurring on the lens surface can be suppressed. In the present invention, distortion and astigmatism can be corrected particularly well when applied to the first lens group, and spherical aberration and coma aberration can be corrected particularly well when applied to the second lens group.

  As in Examples 1 to 4 described later, the second lens group is arranged with a three-piece cemented lens having positive refractive power and a lens having negative refractive power in order from the object side, or Example 5 described later. In order from the object side as in the case of ˜8, a positive single lens, and a cemented lens of a positive lens and a negative lens are used to reduce the beam height of the negative lens, thereby reducing the Petzval sum and suppressing the curvature of field. Can do. When the second lens group is configured with four lenses as in Examples 1 to 4, or when configured with three lenses as in Examples 5 to 8, when trying to configure with only a single lens, It is decomposed into three or more lens elements, and error factors such as lens eccentricity and lens interval change increase. In particular, when the second lens unit is thinned in pursuit of compactness, the eccentricity error sensitivity, surface shape error sensitivity, thickness / interval error sensitivity, etc. of each lens element increase, It becomes necessary to greatly increase the positioning accuracy in the optical axis direction, and the productivity is deteriorated. If a cemented lens is used as in this embodiment, it is sufficient to manage substantially two lens elements, and productivity can be improved relatively. In addition, any cemented lens exhibits great power in suppressing chromatic aberration. As described above, since the aberration generated in the second lens group can be suppressed to a small value, aberration variation during zooming can be reduced.

  By forming the first lens group with two lenses, a negative lens and a positive lens in order from the object side, a compact optical system with a small lens thickness and a small front lens diameter can be achieved. If a negative lens, a negative lens, and a positive lens are used, the negative power can be divided and reduced, so that negative distortion generated in this group can be corrected well, but the compactness is lost. It will be broken. In addition, by using an aspheric surface for the first lens group, it is possible to effectively correct distortion, astigmatism, and the like. In particular, by combining a spherical lens using a translucent ceramic with a high refractive index and an aspherical resin, the effect of correcting the aberration is increased compared to a glass mold lens or a plastic lens.

  In the present invention, the third lens group is composed of one positive lens. However, in this lens type, there is no optical element having power after the third lens group. Subsequent ray paths are not magnified and are not noticeable. Therefore, even if two or more positive and negative lenses are not necessarily achromatic in this group, the influence on the optical performance of the entire system is small, and a simple configuration with one positive lens may be used. Furthermore, by using a plastic lens that is lighter than glass for this group, it is possible to further reduce the load applied to the drive mechanism when the third lens group is moved by zooming or focusing. When a plastic lens is used for the third lens group, the magnification of this group is relatively small, the height of the on-axis light beam passing therethrough is low, and the thickness of the off-axis light beam is thin. Even if a change occurs, the amount of focus movement is relatively small, and the deterioration in optical performance can be small. The use of plastic lenses also contributes to cost reduction of the lenses. Even when a glass mold aspherical surface or a composite (hybrid) aspherical surface is used for the third lens group, good optical performance can be maintained.

  This zoom lens employs a so-called rear focus that moves the third lens unit to the object side when focusing from an object at infinity to an object at a short distance. When trying to focus with the first lens group, the front lens diameter becomes large in order to secure the peripheral light quantity ratio at a close distance. However, focusing by the third group does not do so, so that compactness can be maintained. it can.

  Next, conditional expressions of the zoom lens according to the present invention will be described.

  Conditional expressions (1), (2), (5), and (6) define the refractive index and chromatic dispersion when two types of translucent ceramic lenses are applied to the negative lens in the first lens group. It is a thing. If this value is equal to or greater than the lower limit, as described above, the refractive index is sufficiently high and the chromatic dispersion is small, so that distortion, astigmatism, and chromatic aberration can be corrected well. In particular, conditional expression (1) is highly effective in suppressing distortion and astigmatism, and conditional expression (6) is effective in suppressing lateral chromatic aberration. Desirably, conditional expressions (3) and (4) are preferably satisfied.

  Conditional expressions (9), (10), (13), and (14) define the refractive index and chromatic dispersion when two types of translucent ceramic lenses are applied to the positive lens in the second lens group. It is a thing. If this value is equal to or greater than the lower limit, as described above, since the refractive index is sufficiently high and the chromatic dispersion is small, spherical aberration, coma aberration, and chromatic aberration can be corrected well. In particular, conditional expression (9) is highly effective in suppressing spherical aberration and coma, and conditional expression (14) is effective in suppressing axial chromatic aberration. Desirably, conditional expressions (11) and (12) are preferably satisfied.

  Conditional expression (7) defines the relationship between the focal length of the first lens group and the focal length of the entire system at the telephoto end. If this value is greater than or equal to the lower limit value, the aberration of the first lens group becomes too large due to the power of the first lens group becoming too large, and good optical performance can be maintained. On the other hand, if this value is less than or equal to the upper limit value, the power of the first lens group becomes too small, the lateral magnification after the second lens group becomes small, and as a result, the entire lens length becomes long and the compactness is impaired. There is no such thing. Desirably, conditional expression (8) is preferably satisfied.

  Conditional expression (15) defines the relationship between the focal length of the second lens group and the focal length of the entire system at the telephoto end. If this value is greater than or equal to the lower limit value, the aberration of the second lens group is not increased too much due to the power of the second lens group becoming too large, and good optical performance can be maintained. On the other hand, if this value is less than or equal to the upper limit value, the power of the second lens group becomes too small, which increases the amount of movement of the second lens group at the time of zooming, resulting in a longer overall lens length and a loss of compactness. There is no such thing. Desirably, conditional expression (16) is preferably satisfied.

  Conditional expression (17) defines the relationship between the refractive power of the entire system at the telephoto end and the refractive power of the third lens group. If this value is equal to or greater than the lower limit, the power of the third lens group becomes too small, and the amount of movement during focusing does not increase so much that the compactness is not impaired. On the other hand, if this value is less than or equal to the upper limit value, the power of the third lens group does not increase too much, and distortion and astigmatism generated in this group, lens eccentricity error, lens surface shape error, lens thickness / interval Optical performance deterioration due to errors or the like can be small, and good optical performance can be maintained. If this group is made of plastic lenses, the amount of focus movement when the temperature changes can be kept small. Desirably, conditional expression (18) is preferably satisfied.

  Conditional expression (19) defines the relationship between the sum of the axial thicknesses of the lens groups and the diagonal length of the image sensor. If this value is equal to or greater than the lower limit, the lens thickness is not too thin, so that optical performance degradation due to lens decentration error, lens surface shape error, lens thickness / interval error, etc. is small, and good optical performance is maintained. be able to. If this value is less than or equal to the upper limit value, the lens thickness becomes too thick and the compactness is not impaired. Desirably, conditional expression (20) is preferably satisfied.

  Examples relating to the zoom lens of the present invention are shown below.

  In addition, the code | symbol shown below is as follows.

f: Focal length of the entire system F: F number ω: Half angle of view R: Radius of curvature d: Lens interval n _d : Refractive index for d-line ν _d : Abbe number The aspherical shape is the origin of the surface Where X is taken in the direction of the optical axis, and the height in the direction perpendicular to the optical axis is h.

However,
A _i : i-order aspherical coefficient R: radius of curvature K: conical constant In the lens configuration diagrams in each example, members positioned behind the final lens surface are a low-pass filter and a cover glass in order from the front.
(Example 1)
The overall specifications are shown below.

f = 8.14-22.93
F = 2.88-5.28
ω = 31.2 ° to 11.6 °
Lens data is shown in Table 1.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fifth lens is a spherical translucent ceramic lens, and the seventh lens is a plastic aspherical lens. It is.

  Table 2 shows the aspheric coefficients.

  Table 3 shows variable lens intervals.

  Table 4 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 1 is a lens configuration diagram at the wide-angle end.

  FIG. 2 is an aberration diagram at the wide-angle end.

  FIG. 3 is an aberration diagram at the intermediate focal length.

FIG. 4 is an aberration diagram at the telephoto end.
(Example 2)
The overall specifications are shown below.

f = 8.14-22.93
F = 2.88-5.28
ω = 31.2 ° to 11.6 °
Table 5 shows the lens data.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fifth lens is a spherical translucent ceramic lens, and the seventh lens is a plastic aspherical lens. It is.

  Table 6 shows the aspheric coefficients.

  Table 7 shows the variable lens intervals.

  Table 8 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 5 is a lens configuration diagram at the wide-angle end.

  FIG. 6 is an aberration diagram at the wide-angle end.

  FIG. 7 is an aberration diagram at the intermediate focal length.

FIG. 8 is an aberration diagram at the telephoto end.
(Example 3)
The overall specifications are shown below.

f = 8.14-22.93
F = 2.88-5.28
ω = 31.2 ° to 11.6 °
Table 9 shows the lens data.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fifth lens is a spherical translucent ceramic lens, and the seventh lens is a plastic aspherical lens. It is.

  Table 10 shows the aspheric coefficients.

  Table 11 shows variable lens intervals.

  Table 12 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 9 is a lens configuration diagram at the wide-angle end.

  FIG. 10 is an aberration diagram at the wide-angle end.

  FIG. 11 is an aberration diagram at the intermediate focal length.

FIG. 12 is an aberration diagram at the telephoto end.
Example 4
The overall specifications are shown below.

f = 8.14-22.93
F = 2.88-5.28
ω = 31.2 ° to 11.6 °
Lens data is shown in Table 13.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fifth lens is a spherical translucent ceramic lens, and the seventh lens is a plastic aspherical lens. It is.

  Table 14 shows the aspheric coefficients.

  Table 15 shows variable lens intervals.

  Table 16 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 13 is a lens configuration diagram at the wide-angle end.

  FIG. 14 is an aberration diagram at the wide-angle end.

  FIG. 15 is an aberration diagram at the intermediate focal length.

FIG. 16 is an aberration diagram at the telephoto end.
(Example 5)
The overall specifications are shown below.

f = 8.25-23.35
F = 2.88 to 5.05
ω = 30.9 ° to 11.4 °
Lens data is shown in Table 17.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fourth lens is a spherical translucent ceramic lens, and the sixth lens is a plastic aspherical lens. It is.

  Table 18 shows the aspheric coefficients.

  Table 19 shows variable lens intervals.

  Table 20 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 17 is a lens configuration diagram at the wide-angle end.

  FIG. 18 is an aberration diagram at the wide-angle end.

  FIG. 19 is an aberration diagram at the intermediate focal length.

FIG. 20 is an aberration diagram at the telephoto end.
(Example 6)
The overall specifications are shown below.

f = 8.25-23.35
F = 2.88 to 5.05
ω = 30.9 ° to 11.4 °
Table 21 shows the lens data.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fourth lens is a spherical translucent ceramic lens, and the sixth lens is a plastic aspherical lens. It is.

  Table 22 shows the aspheric coefficients.

  Table 23 shows variable lens intervals.

  Table 24 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 21 is a lens configuration diagram at the wide-angle end.

  FIG. 22 is an aberration diagram at the wide-angle end.

  FIG. 23 is an aberration diagram at the intermediate focal length.

FIG. 24 is an aberration diagram at the telephoto end.
(Example 7)
The overall specifications are shown below.

f = 8.25-23.35
F = 2.88 to 5.05
ω = 30.9 ° to 11.4 °
Lens data is shown in Table 25.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fourth lens is a spherical translucent ceramic lens, and the sixth lens is a plastic aspherical lens. It is.

  Table 26 shows the aspheric coefficients.

  Table 27 shows the variable lens intervals.

  Table 28 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 25 is a lens configuration diagram at the wide-angle end.

  FIG. 26 is an aberration diagram at the wide-angle end.

  FIG. 27 is an aberration diagram at the intermediate focal length.

FIG. 28 is an aberration diagram at the telephoto end.
(Example 8)
The overall specifications are shown below.

f = 8.25-23.35
F = 2.88 to 5.05
ω = 30.9 ° to 11.4 °
Lens data is shown in Table 29.

  However, the first lens is a composite aspherical lens composed of a spherical translucent ceramic lens and an aspherical resin layer, the fourth lens is a spherical translucent ceramic lens, and the sixth lens is a plastic aspherical lens. It is.

  Table 30 shows the aspheric coefficients.

  Table 31 shows variable lens intervals.

  Table 32 shows the amount of focus movement due to the temperature change of the plastic lens.

  FIG. 29 is a lens configuration diagram at the wide-angle end.

  FIG. 30 is an aberration diagram at the wide-angle end.

  FIG. 31 is an aberration diagram at the intermediate focal length.

  FIG. 32 is an aberration diagram at the telephoto end.

  Finally, Table 33 shows values corresponding to the conditional expressions 1 to 20 in Examples 1 to 8.

FIG. 3 is a lens configuration diagram at a wide angle end in the zoom lens of Example 1; FIG. 3 is an aberration diagram at a wide-angle end in the zoom lens according to Example 1; FIG. 4 is an aberration diagram at an intermediate focal length in the zoom lens of Example 1; FIG. 3 is an aberration diagram at a telephoto end in the zoom lens according to Example 1; 6 is a lens configuration diagram at a wide angle end in a zoom lens according to Embodiment 2; FIG. 6 is an aberration diagram at a wide-angle end in the zoom lens according to Example 2. FIG. 6 is an aberration diagram at an intermediate focal length in the zoom lens of Example 2. FIG. FIG. 6 is an aberration diagram at a telephoto end in the zoom lens according to Example 2; 6 is a lens configuration diagram at a wide angle end in a zoom lens according to Embodiment 3; FIG. 6 is an aberration diagram at a wide-angle end in the zoom lens according to Example 3; FIG. FIG. 10 is an aberration diagram at an intermediate focal length in the zoom lens according to Example 3; FIG. 6 is an aberration diagram at a telephoto end in the zoom lens according to Example 3; 6 is a lens configuration diagram at a wide angle end in a zoom lens according to Embodiment 4; FIG. FIG. 10 is an aberration diagram at a wide-angle end in the zoom lens according to Example 4; FIG. 10 is an aberration diagram at an intermediate focal length in the zoom lens according to Example 4; FIG. 6 is an aberration diagram at a telephoto end in the zoom lens according to Example 4; 6 is a lens configuration diagram at a wide-angle end in a zoom lens according to Example 5. FIG. FIG. 10 is an aberration diagram at a wide-angle end in the zoom lens according to Example 5; FIG. 10 is an aberration diagram at an intermediate focal length in the zoom lens according to Example 5; FIG. 10 is an aberration diagram at a telephoto end in the zoom lens according to Example 5; 10 is a lens configuration diagram at a wide-angle end in a zoom lens according to Example 6. FIG. FIG. 10 is an aberration diagram at a wide-angle end in the zoom lens according to Example 6; 10 is an aberration diagram at an intermediate focal length in the zoom lens according to Example 6; FIG. 10 is an aberration diagram at a telephoto end in the zoom lens according to Example 6; FIG. 12 is a lens configuration diagram at a wide-angle end in a zoom lens according to Example 7. FIG. 10 is an aberration diagram at a wide-angle end in the zoom lens according to Example 7. FIG. 10 is an aberration diagram at an intermediate focal length in the zoom lens of Example 7. FIG. 10 is an aberration diagram at a telephoto end in the zoom lens according to Example 7. FIG. FIG. 10 is a lens configuration diagram at a wide-angle end in a zoom lens according to Example 8; 10 is an aberration diagram at a wide-angle end in the zoom lens according to Example 8. FIG. FIG. 10 is an aberration diagram at an intermediate focal length in the zoom lens according to Example 8; 10 is an aberration diagram at a telephoto end in the zoom lens according to Example 8; FIG.

Claims (19)

In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The zoom lens according to claim 1, wherein the first lens group includes at least one negative lens and satisfies the following conditional expression.
1.9 <n _1n
35 <ν _1n
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens The zoom lens according to claim 1, wherein the negative lens satisfies the following conditional expression.
2.0 <n _1n
40 ≦ ν _1n
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The zoom lens according to claim 1, wherein the first lens group includes at least one negative lens and satisfies the following conditional expression.
1.8 <n _1n
50 <ν _1n
However,
n _1n : refractive index of the negative lens ν _1n : Abbe number of the negative lens The zoom lens according to claim 1, wherein the negative lens uses translucent ceramics. The zoom lens according to claim 1, wherein the negative lens is a composite aspherical lens in which an aspherical resin layer is formed on a spherical lens made of translucent ceramics. The zoom lens according to claim 1, wherein the first lens group satisfies the following conditional expression.
−1.5 <f ₁ / f _T <−0.5
However,
f ₁ : focal length of the first lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to claim 1, wherein the first lens group satisfies the following conditional expression.
−1.1 <f ₁ / f _T <−0.7
However,
f ₁ : focal length of the first lens group f _T : focal length of the entire system at the telephoto end In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The second lens group has at least one positive lens, and satisfies the following conditional expression:
1.9 <n _2p
35 <ν _2p
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens The zoom lens according to claim 8, wherein the positive lens satisfies the following conditional expression.
2.0 <n _2p
40 ≦ ν _2p
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and changing from the wide-angle end to the telephoto end. In the zoom lens that changes the magnification by changing the interval of each lens group,
The second lens group has at least one positive lens, and satisfies the following conditional expression:
1.8 <n _2p
50 <ν _2p
However,
n _2p : refractive index of the positive lens ν _2p : Abbe number of the positive lens The zoom lens according to claim 8, wherein the positive lens uses translucent ceramics. The zoom lens according to any one of claims 8 to 11, wherein the second lens group satisfies the following conditional expression.
0.3 <f ₂ / f _T <0.9
However,
f ₂ : focal length of the second lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to any one of claims 8 to 11, wherein the second lens group satisfies the following conditional expression.
0.4 <f ₂ / f _T <0.8
However,
f ₂ : focal length of the second lens group f _T : focal length of the entire system at the telephoto end The zoom lens according to any one of claims 1 to 13, wherein the second lens group includes a three-piece cemented lens including a positive lens, a negative lens, and a positive lens in order from the object side. . The zoom lens according to any one of claims 1 to 14, wherein the third lens group includes one positive lens made of plastic and satisfies the following conditional expression.
0.5 <f _T / f ₃ <1.5
However,
f _T : focal length of the entire system at the telephoto end f ₃ : focal length of the third lens group The zoom lens according to any one of claims 1 to 14, wherein the third lens group includes one positive lens made of plastic and satisfies the following conditional expression.
0.8 <f _T / f ₃ <1.2
However,
f _T : focal length of the entire system at the telephoto end f ₃ : focal length of the third lens group The zoom lens according to claim 1, wherein the zoom lens moves at least the third lens group to perform focusing from infinity to a finite distance. The zoom lens according to claim 1, wherein the zoom lens satisfies the following conditional expression.
1.0 <SD / 2Y <2.0
However,
SD: Sum of axial thickness of each lens group 2Y: Diagonal length of image sensor The zoom lens according to claim 1, wherein the zoom lens satisfies the following conditional expression.
1.2 <SD / 2Y <1.7
However,
SD: Sum of axial thickness of each lens group 2Y: Diagonal length of image sensor

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