JP2005091992A - Zoom lens and camera system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens which realizes the imaging performance corresponding to an imaging device having 3 to 5 million pixels. <P>SOLUTION: The zoom lens has a first group I having a negative focal length, a second group II having a positive focal length, a third group III having a negative focal length, a fourth group IV having a positive focal length and being fixed when varying the power, a fifth group V having a positive focal length arranged in order from the object side and has a stop S moving together with the third group as one body, on the object side of the third group, and the first group I consists of a first negative meniscus lens L1 having a convex directed to the object side, a second positive lens L2, and a third negative lens L3 in order from the object side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a zoom lens and a camera device.

  With the widespread use of digital cameras, user demands for digital cameras have also increased. In other words, there has been a strong demand for a wide angle of view of the photographic lens, not to mention high image quality and downsizing, and the “half angle of view at the short focal point” of the zoom lens used as the photographic lens is desired to be 38 degrees or more. Yes. In addition, there is a great demand for a high zoom ratio of the photographing lens, and a zoom ratio of 4 times or more is desired.

  There are many types of zoom lenses for digital cameras. As a type suitable for widening the angle of view, a so-called “negative leading type” zoom lens in which the first group closest to the object side has a negative focal length is known. Various types of “negative / positive / negative / positive / positive 5-group zoom lenses” have been proposed (Patent Documents 1 to 3).

  In recent years, the number of pixels in digital cameras has increased dramatically, with 3 to 5 million pixels becoming mainstream, and zoom lenses used in digital cameras also have good results suitable for such an image sensor with a large number of pixels. Image performance is required.

  In order to appropriately cope with the downsizing of the digital camera, it is necessary to reduce the size of the zoom lens. In that case, it is indispensable to reduce the lens diameter of the first group.

JP-A-5-107476 JP-A-5-323196 JP 2000-305017 A

  In view of the circumstances described above, the present invention is capable of realizing an imaging performance suitable for an image sensor with 3 to 5 million pixels, and a zoom lens in which the lens diameter of the first lens group is reduced to facilitate compactness, and the zoom lens. It is an object of the present invention to provide a camera device that uses the camera.

  As illustrated in FIG. 1, the zoom lens according to the present invention includes, in order from the object side (left side in the figure), a first group I having a negative focal length, a second group II having a positive focal length, and a negative A third group III having a focal length, a fourth group IV having a positive focal length and fixed at the time of zooming, a fifth group V having a positive focal length, and a third group III on the object side of the third group III. The first group I includes, in order from the object side, a negative meniscus first lens L1, a positive second lens L2, and a negative third lens L3 with a convex surface facing the object side. (Claim 1).

  When zooming from the short focal end to the long focal end, the zoom lens according to claim 1 is configured such that the distance between the first group I and the second group II is narrowed as illustrated in FIG. The air spacing of each lens group is changed so that the distance between the third group III is widened, the distance between the third group III and the fourth group IV is widened, and the distance between the fourth group IV and the fifth group V is narrowed. (Claim 2).

The zoom lens according to claim 1 or 2, wherein the refractive index: N ₁ and Abbe number: ν ₁ of the first lens L1 in the first group I, and the refractive index: N ₂ and Abbe of the second lens L2 in the first group I. Number: ν ₂ , condition:
(1) 1.74 <N ₁ <1.95
(2) 1.74 <N ₂ <1.95
(3) ν ₁ -ν ₂ > 20
Is preferably satisfied (Claim 3).

The zoom lens according to any one of claims 1 to 3 has a configuration in which at least the second lens L2 and the third lens L3 of the first group I are cemented, as illustrated in FIG. (Claim 4). In this case, the radius of curvature of the object side surface of the second lens L2 in the second lens and the third lens joined in the first group I: R _cf , and the radius of curvature of the image side surface of the third lens L3: R _cr are:
(4) 1.8 <R _cf / R _cr <2.6
Is preferably satisfied (Claim 5).

In the zoom lens according to any one of claims 1 to 5, it is preferable that the image side surface of the negative lens in the first lens unit I be an aspherical surface (claim 6).
The zoom lens according to any one of claims 1 to 6, wherein the fifth group V can be composed of "a single positive lens having at least one aspheric surface". The refractive index of the positive lens of the fifth group: N _g5 , Abbe number: ν _g5 , conditions:
(5) 1.45 <N _g5 <1.65
(6) 55 <ν _g5 <75
Is preferably satisfied (claim 8).
The zoom lens according to an eighth aspect of the present invention may have a “configuration in which focusing is performed by the fifth group” (Claim 9). Of course, in the zoom lens other than claim 8, focusing can be performed by the fifth group, and focusing can be performed by a group other than the fifth group.

  The camera device of the present invention is characterized by having “the zoom lens according to any one of claims 1 to 9 as a photographing optical system”. It goes without saying that such a “camera device” can be implemented as a digital camera, as well as a silver halide photographic camera. The camera device can also be implemented as a “portable information terminal device”.

The so-called “negative leading type” negative / positive / negative / positive / positive 5-group zoom is suitable for high zoom lenses with a zoom ratio of 4x or more from 28 mm with a focal length equivalent to a silver halide camera. ing.
In the zoom lens configuration preceded by the negative lens group, it is known that the diameter of the first group can be made relatively small. However, when the half angle of view is close to 40 °, “further innovation” is required.

  In the zoom lens according to the present invention, in order to reduce the diameter of the first lens group, the first lens unit includes three lenses, a negative meniscus lens having a convex surface facing the object side, a positive lens, and a negative lens, from the object side. Arranged in the above order.

When the off-axis lower ray is “tracked from the image plane” in the first group configuration, the off-axis lower ray is once spread outward by the negative third lens of the first group, and the positive second lens. After being bent inward by the first lens, it is expanded outward again by the first lens which is a negative meniscus lens. In this manner, in the first group, “negative lenses and positive lenses are alternately arranged in a negative, positive, and negative manner” to prevent an increase in the front lens diameter.
It is conceivable that the configuration of the first group is a “two-lens configuration of a negative meniscus lens and a biconvex lens”, but it is difficult to sufficiently secure “image performance at the wide-angle end” with the two-lens configuration.

  The zoom lens according to the present invention also has a five-group configuration of negative, positive, negative, positive, and positive to increase the “degree of freedom in correcting the image plane position”, so that the number of lenses can be increased to 10 while maintaining sufficient performance. It is possible to reduce the number of lenses, and by fixing the fourth lens unit at the time of zooming, it is possible to simplify the “lens barrel structure” and reduce the manufacturing error sensitivity, which is sufficiently high at low cost. A high-performance zoom lens can be realized.

  As described in claim 2, upon zooming from the short focal end to the long focal end, the distance between the first group I and the second group II is narrowed, and the distance between the second group II and the third group III is widened. By changing the air spacing of each lens group so that the distance between the third group III and the fourth group IV is widened and the distance between the fourth group IV and the fifth group V is narrowed, the “shorter than the total length of the zoom lens”. ”Is possible.

In the conditions (1) and (2), when the refractive indexes N ₁ and N _{2 of} the first lens L1 and the second lens L2 are 1.74 or less, the power of the lenses L1 and L2 is insufficient and the total length increases. . Further, the upper limit value of the conditions (1) and (2): A glass material having a refractive index of 1.95 or more is expensive, which causes an increase in cost.

When the value of the parameter (ν ₁ −ν ₂ ) of condition (3) is 20 or less, the ability to correct lateral chromatic aberration off-axis is insufficient, leading to performance degradation.
The refractive index: N ₁ of the first lens L1 is slightly narrower than the condition (1):
(1A) 1.74 <N ₁ <1.85
It is more preferable to satisfy the refractive index of the second lens L2: N ₂ is slightly narrower conditions than Condition (2):
(2A) 1.80 <N ₂ <1.85
Is more preferable.

  In order to reduce the performance deterioration due to the lens assembly error, it is preferable to “join at least the positive second lens L2 of the first group and the negative third lens L3 on the image side” as described in claim 4. . Since “aberration in a direction that cancels each other” occurs greatly on the image side surface of the positive second lens L2 and the object side surface of the negative third lens L3, “image performance due to relative decentration” of these two lenses L2 and L3. “Deterioration of image quality” is particularly large on the short focus side, but by joining these two lenses L2 and L3, such image performance deterioration can be prevented. At that time, satisfying the condition (4) makes it possible to further enhance the performance of the zoom lens.

Condition (4) parameter: When R _cf / R _cr is 1.8 or less, the positive power of the first lens group is weakened and hinders downsizing, and when it is 2.6 or more, off-axis aberration correction is excessive. It becomes difficult to obtain good image performance. Parameter: R _cf / R _cr is the condition:
(4A) 1.8 <R _cf / R _cr <2.0
Is more preferable.

  In order to correct the lateral chromatic aberration more satisfactorily, it is preferable that “the image side surface of the negative lens in the first group is at least one aspherical surface” as described in claim 6. The image side surfaces of these negative lenses are “strong concave surfaces”, and making these surfaces aspherical surfaces is particularly effective for “aberration correction of off-axis rays on the short focal side”. More preferably, the first lens of the first group is provided with an aspherical surface.

  According to the seventh aspect of the present invention, it is possible to further reduce the overall length by configuring the fifth group with “a single lens having at least one aspheric surface”. By using an aspherical surface, it is possible to suppress the “decrease in aberration correction ability due to the single lens” in the fifth group. At that time, it is preferable to satisfy the conditions (5) and (6) in order to minimize the deterioration of the image performance due to the miniaturization.

When the refractive index: N _g5 is 1.45 or less and the Abbe number: ν _g5 is 75 or more, the power required for the fifth group becomes too weak to prevent downsizing, and the refractive index: N _g5 is 1. If the Abbe's number ν _g5 is 55 or less at .65 or more, the chromatic aberration generated in the first group with a large amount of high dispersion glass cannot be corrected and the image performance deteriorates. Refractive index: N _g5 is slightly narrower than condition (5):
(5A) 1.60 <N _g5 <1.63
It is more preferable to satisfy.

  By performing “focusing in the fifth group” as described in claim 9, it is possible to achieve a simpler and higher performance. In this case, since the fifth group is composed of “one lens”, the focusing mechanism can be simplified.

  The most object side surface of the third group is in the vicinity of the “aperture”, and the marginal ray has a sufficient height, and the change in the ray height due to zooming is small, so an aspheric surface is provided at this position. As a result, spherical aberration, which is the basis of imaging performance, can be corrected more satisfactorily.

According to the present invention, a novel zoom lens can be realized.
In the zoom lens of the present invention, as shown in the aberration diagrams for each of the embodiments described later, the aberration is sufficiently corrected, and it is possible to realize an imaging performance suitable for an image sensor with 3 to 5 million pixels. In addition, the lens diameter of the first group can be reduced to achieve a sufficient size reduction, and by using this, a compact and high-performance camera device (digital camera or portable information terminal device) can be realized.

  Hereinafter, four specific numerical examples will be given as the best mode for carrying out the zoom lens of the present invention.

  The meanings of symbols in each embodiment are as follows.

f: Focal length of the entire system F: F number
ω: Half angle of view
R: radius of curvature
D: Surface spacing
N _d : Refractive index for d-line
ν _d : Abbe number
K: Aspherical conical constant
A ₄ : Fourth-order aspheric coefficient
A ₆ : 6th-order aspheric coefficient
A ₈ : 8th-order aspheric coefficient
A ₁₀ : 10th-order aspheric coefficient
“Aspherical surface” means depth in the optical axis direction: X, reciprocal of paraxial radius of curvature (paraxial curvature): C, height from optical axis: H, conic constant: K, aspheric coefficient: A _{4 to} A ₁₀ is represented by the following well-known formula.

X = CH ² / [1 + √ (1- (1 + K) C ² H ² )] + A ₄ · H ⁴ + A ₆ · H ⁶ + A ₈ · H ⁸ + A ₁₀ · H ¹⁰

f = 5.95 to 28.35, F = 2.76 to 4.72, ω = 39.0 to 9.06
The specifications of Example 1 are shown in Table 1.

  Surfaces marked with * are aspheric surfaces.

Aspheric:
Second side
K = 0.0, A ₄ = -0.963006 × 10 ^-5 , A ₆ = -0.454737 × 10 ^-6 , A ₈ = 0.358262 × 10 ^-8 ,
A ₁₀ = -0.209815 × 10 ^-10
10th page
K = 0.0, A ₄ = -0.562251 × 10 ^-4 , A ₆ = 0.211170 × 10 ^-6 , A ₈ = 0.386269 × 10 ^-8 ,
A ₁₀ = -0.440001 × 10 ^-10
12th page
K = 0.0, A ₄ = -0.269750 × 10 ^-3 , A ₆ = 0.464757 × 10 ^-5 , A ₈ = -0.107300 × 10 ^-5 ,
A ₁₀ = 0.451648 × 10 ^-7
14th page
K = 0.0, A ₄ = 0.918427 × 10 ^-4 , A ₆ = 0.562067 × 10 ^-5 , A ₈ = -0.157081 × 10 ^-6 ,
A ₁₀ = 0.195780 × 10 ^-8
17th page
K = 0.0, A ₄ = -0.142400 × 10 ^-3 , A ₆ = -0.575056 × 10 ^-5 , A ₈ = 0.703135 × 10 ^-7 ,
A ₁₀ = -0.871864 × 10 ^-9 .

Variable amount The variable amount in Example 1 is shown in Table 2.

The parameter values of the conditional expression are as follows.
N ₁ = 1.77250
N ₂ = 1.84666
ν ₁ -ν ₂ = 25.84
R _cf / R _cr = 2.40
N _g5 = 1.62041
ν _g5 = 60.34.

f = 5.95 to 28.13, F = 2.80 to 4.93, ω = 39.3 to 9.14
The specifications of Example 2 are shown in Table 3.

  Surfaces marked with * are aspheric surfaces.

Aspheric:
Second side
K = 0.0, A ₄ = -0.233177 × 10 ^-5 , A ₆ = -0.860234 × 10 ^-6 , A ₈ = 0.779755 × 10 ^-8 ,
A ₁₀ = -0.478004 × 10 ^-10
6th page
K = 0.0, A ₄ = 0.537739 × 10 ^-4 , A ₆ = -0.557957 × 10 ^-7 , A ₈ = 0.173824 × 10 ^-8 ,
A ₁₀ = -0.312791 × 10 ^-10
12th page
K = 0.0, A ₄ = -0.338678 × 10 ^-3 , A ₆ = -0.175116 × 10 ^-5 , A ₈ = -0.641093 × 10 ^-6 ,
A ₁₀ = 0.242101 × 10 ^-7
14th page
K = 0.0, A ₄ = 0.498242 × 10 ^-4 , A ₆ = 0.189885 × 10 ^-4 , A ₈ = -0.998546 × 10 ^-6 ,
A ₁₀ = 0.202646 × 10 ^-7
17th page
K = 0.0, A ₄ = -0.938814 × 10 ^-4 , A ₆ = -0.187859 × 10 ^-4 , A ₈ = 0.723542 × 10 ^-6 ,
A ₁₀ = -0.127225 × 10 ^-7 .

Variable amount The variable amount in Example 2 is shown in Table 4.

  The parameter values of the conditional expression are as follows.

N ₁ = 1.77250
N ₂ = 1.84666
ν ₁ -ν ₂ = 25.84
R _cf / R _cr = 1.88
N _g5 = 1.62299
ν _g5 = 58.12.

f = 5.93 to 28.13, F = 2.77 to 4.62, ω = 39.29 to 9.14
The specifications of Example 3 are shown in Table 5.

  Surfaces marked with * are aspheric surfaces.

Aspheric:
Second side
K = 0.0, A ₄ = 0.405290 × 10 ^-5 , A ₆ = -0.795512 × 10 ^-6 , A ₈ = 0.731585 × 10 ^-8 ,
A ₁₀ = -416873 × 10 ^-10
6th page
K = 0.0, A ₄ = 0.446660 × 10 ^-4 , A ₆ = -0.337965 × 10 ^-6 , A ₈ = 0.101651 × 10 ^-7 ,
A ₁₀ = -0.116154 × 10 ^-9
12th page
K = 0.0, A ₄ = -0.336618 × 10 ^-3 , A ₆ = 0.425198 × 10 ^-5 , A ₈ = -0.224469 × 10 ^-5 ,
A ₁₀ = 0.143198 × 10 ^-6
14th page
K = 0.0, A ₄ = 0.954291 × 10 ^-4 , A ₆ = 0.133137 × 10 ^-4 , A ₈ = -0.754432 × 10 ^-6 ,
A ₁₀ = 0.145586 × 10 ^-7
19th page
K = 0.0, A ₄ = 0.113607 × 10 ^-3 , A ₆ = 0.226989 × 10 ^-4 , A ₈ = -0.854860 × 10 ^-6 ,
A ₁₀ = 0.138284 × 10 ⁻⁷ .

Variable amount The variable amount in Example 3 is shown in Table 6.

  The parameter values of the conditional expression are as follows.

N ₁ = 1.77250
N ₂ = 1.80518
ν ₁ -ν ₂ = 24.16
R _cf / R _cr = 1.87
N _g5 = 1.48749
ν _g5 = 70.40.

f = 5.95 to 28.13, F = 2.80 to 4.38, ω = 39.22 to 9.15
The specifications of Example 4 are shown in Table 7.

  Surfaces marked with * are aspheric surfaces.

Aspheric:
Second side
K = 0.0, A ₄ = -0.644192 × 10 ^-5 , A ₆ = -0.665920 × 10 ^-6 , A ₈ = 0.611167 × 10 ^-8 ,
A ₁₀ = -0.388962 × 10 ^-10
6th page
K = 0.0, A ₄ = -0.163618 × 10 ^-5 , A ₆ = -0.783480 × 10 ^-6 , A ₈ = 0.174955 × 10 ^-7 ,
A ₁₀ = -0.101438 × 10 ^-9
10th page
K = 0.0, A ₄ = -0.494770 × 10 ^-4 , A ₆ = -0.299728 × 10 ^-6 , A ₈ = 0.173433 × 10 ^-7 ,
A ₁₀ = -0.153367 × 10 ^-9
12th page
K = 0.0, A ₄ = -0.321557 × 10 ^-3 , A ₆ = -0.304044 × 10 ^-5 , A ₈ = -0.428406 × 10 ^-6 ,
A ₁₀ = 0.331738 × 10 ^-7
14th page
K = 0.0, A ₄ = 0.250341 × 10 ^-3 , A ₆ = 0.369364 × 10 ^-5 , A ₈ = -0.803657 × 10 ^-7 ,
A ₁₀ = 0.527731 × 10 ^-9
18th page
K = 0.0, A ₄ = 0.308986 × 10 ^-3 , A ₆ = 0.600465 × 10 ^-5 , A ₈ = 0.111924 × 10 ^-7 ,
A ₁₀ = 0.178163 × 10 ^-9 .

Variable amount The variable amount in Example 4 is shown in Table 8.

  The parameter values of the conditional expression are as follows.

N ₁ = 1.80420
N ₂ = 1.84666
ν ₁ -ν ₂ = 22.72
R _cf / R _cr = 1.83
N _g5 = 1.62041
ν _g5 = 60.34.

1-4 sequentially show the “lens configuration” of the zoom lenses of Examples 1 to 4 and “the state of movement of each group during zooming”.
5 to 7 show aberration diagrams at the short focal end, the intermediate focal length, and the long focal end in Example 1 in the order described above. Similarly, FIGS. 8 to 10 show aberration diagrams at the short focal end, intermediate focal length, and long focal end for Example 2, and FIGS. 11 to 13 show short focal end, intermediate focal length, and long focal length for Example 3. Aberration diagrams at the focal end and FIGS. 14 to 16 show aberration diagrams at the short focal end, the intermediate focal length, and the long focal end in Example 4.

  The broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional. As can be seen from each aberration diagram, in Examples 1 to 4, the aberration is sufficiently corrected, and the imaging performance is adequate for an image sensor having 3 to 5 million pixels.

  One embodiment of a camera device (personal digital assistant device) will be described with reference to FIGS.

  As shown in FIG. 18, the camera device includes a photographing lens 181 and an image sensor (area sensor) 182, and is configured to read an image of a photographing object formed by the photographing lens 181 by the image sensor 182. Yes. As the photographing lens 181, the zoom lens according to any one of claims 1 to 9 (specifically, those in Examples 1 to 4) is used (claim 10).

  A captured image formed on the image sensor 182 by the imaging lens 181 is output from the image sensor 182, processed by the signal processing device 183 under the control of the central processing unit 180, and converted into digital information. The image information digitized by the signal processing device 183 is recorded in the semiconductor memory 187 after being subjected to “predetermined image processing” in the image processing device 184 that is controlled by the central processing unit 180.

  The liquid crystal monitor 185 can display an image being photographed, and can display an image recorded in the semiconductor memory 187. The image recorded in the semiconductor memory 187 can be “sent to the outside” using a communication card 186 or the like.

  As shown in FIG. 17A, the taking lens 181 is in the “collapsed state” when the camera device is carried, and when the user operates the power switch 190 to turn on the power, the mirror as shown in FIG. The torso is paid out. At this time, each group of the photographing lens 181 in the lens barrel is, for example, “arrangement of the short focal end”, and the arrangement of each group is changed by operating the zoom lever 193 shown in FIG. , Zooming toward the long focal end can be performed. At this time, the viewfinder 188 is also scaled in conjunction with the change in the angle of view of the photographing lens 181.

  Focusing (performed by movement of the fifth group) is executed by “half-pressing” the shutter button 191. Focusing can also be performed by displacement of the image sensor 182 (see FIG. 18). When the shutter button 191 is further pressed, shooting is performed, and thereafter the above-described processing is performed.

  When the image recorded in the semiconductor memory 187 shown in FIG. 18 is displayed on the liquid crystal monitor 185 or transmitted to the outside using a card or the like, the operation button 195 shown in FIG. 17C is operated. The semiconductor memory 187 and the communication card 185 are inserted into dedicated or general-purpose slots 196 for use.

  By using the zoom lens of the first to fourth embodiments as a photographic lens in the camera device (portable information terminal device) described above, the image quality using the image sensor 182 of the 3 to 5 million pixel class is improved. It can be realized as a small camera device (portable information terminal device).

3 is a cross-sectional view illustrating a configuration of a zoom lens according to Example 1. FIG. 6 is a cross-sectional view illustrating a configuration of a zoom lens according to Example 2. FIG. 6 is a cross-sectional view illustrating a configuration of a zoom lens according to Example 3. FIG. 7 is a cross-sectional view illustrating a configuration of a zoom lens according to Example 4. FIG. FIG. 6 is an aberration curve diagram at the short focal point of the zoom lens according to Example 1; FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens of Example 1; FIG. 6 is an aberration curve diagram at the long focal end of the zoom lens of Example 1; FIG. 6 is an aberration curve diagram at the short focal point of the zoom lens according to Example 2; FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens of Example 2. FIG. 6 is an aberration curve diagram at the long focal end of the zoom lens of Example 2; FIG. 10 is an aberration curve diagram at the short focal end of the zoom lens according to Example 3; FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens of Example 3; FIG. 10 is an aberration curve diagram at the long focal end of the zoom lens according to Example 3; FIG. 6 is an aberration curve diagram at the short focal point of the zoom lens according to Example 4; FIG. 10 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is an aberration curve diagram at the long focal end of the zoom lens according to Example 4; It is a figure which shows one Embodiment of a camera apparatus. It is a block diagram which shows the system of the camera apparatus shown in FIG.

Explanation of symbols

I 1st Group II 2nd Group III 3rd Group IV 4th Group V 5th Group S Aperture L1 1st Group 1st Lens L2 1st Group 2nd Lens L3 3rd Group 3rd Lens

Claims (10)

In order from the object side, a first group having a negative focal length, a second group having a positive focal length, a third group having a negative focal length, a fourth group having a positive focal length and fixed at the time of zooming, A fifth lens unit having a positive focal length, and a stop that moves integrally with the third lens unit on the object side of the third lens unit;
The zoom lens according to claim 1, wherein the first group includes, in order from the object side, a negative meniscus first lens having a convex surface directed toward the object side, a positive second lens, and a negative third lens. The zoom lens according to claim 1.
Upon zooming from the short focal end to the long focal end, the distance between the first group and the second group is narrowed, the distance between the second group and the third group is widened, the distance between the third group and the fourth group is widened, A zoom lens characterized in that the air gap of each group is changed so that the gap between the fourth group and the fifth group becomes narrow. The zoom lens according to claim 1 or 2,
The refractive index: N ₁ and the Abbe number: ν ₁ of the first lens in the first group, and the refractive index: N ₂ and the Abbe number: ν ₂ of the second lens in the first group are as follows:
(1) 1.74 <N ₁ <1.95
(2) 1.74 <N ₂ <1.95
(3) ν ₁ -ν ₂ > 20
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 3,
A zoom lens, wherein at least the second lens and the third lens of the first group are cemented. The zoom lens according to claim 4.
The curvature radius of the object side surface of the second lens in the second and third lenses joined in the first group: R _cf , and the curvature radius of the image side surface of the third lens: R _cr are as _follows :
(4) 1.8 <R _cf / R _cr <2.6
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 5,
A zoom lens, wherein an image side surface of the negative lens in the first group is an aspherical surface. The zoom lens according to any one of claims 1 to 6,
A zoom lens comprising a fifth lens group consisting of one positive lens having at least one aspheric surface. The zoom lens according to claim 7.
Refractive index of the fifth lens group positive lens: N _g5 , Abbe number: ν _g5 , conditions:
(5) 1.45 <N _g5 <1.65
(6) 55 <ν _g5 <75
A zoom lens characterized by satisfying The zoom lens according to claim 8.
A zoom lens characterized in that focusing is performed by the fifth group.   A camera apparatus comprising the zoom lens according to claim 1 as a photographing optical system.

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