JP5983220B2 - Zoom lens, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens, a camera, and a portable information terminal device.

  As digital cameras become widespread and further miniaturization and high image quality of the cameras themselves are required, zoom lenses as imaging lenses are also required to achieve both high performance and miniaturization.

  In addition, many users desire a wider angle of view of the taking lens, and a half angle of view at the short focal point of the zoom lens of about 45 degrees is desired. Furthermore, a large aperture is also required.

  Assuming a wide angle of view, in terms of miniaturization, since the lens diameter direction tends to increase because of the wide angle, it is necessary to reduce the lens diameter.

  In terms of high performance, it is required to have a resolving power corresponding to an image sensor of at least 10 million to 15 million pixels over the entire zoom range.

  In terms of increasing the diameter, it is desired that the F number at the short focal end is 2.0 or less and the F number at the long focal end is about 3.

There are many types of zoom lenses for digital cameras.
As a type suitable for increasing the diameter, there is a four-lens group configuration in which each lens group is changed as follows.

  That is, at the time of zooming, the first lens group moves so as to “convex to the image side”, the second lens group moves to the image side, the third lens group moves to the object side, and the fourth lens group moves to the image side. Move to the object or object side.

  In this type of zoom lens, it is known that the refractive power distribution of the four lens groups is positive, negative, positive, and positive in order from the object side (Patent Documents 1 to 4, etc.).

  In the zoom lenses disclosed in these documents, among the four lens groups, the first lens group is constituted by a positive lens, and the second lens group is constituted by three negative, negative, and positive lenses.

  The zoom lens described in each of the above patent documents has a large aperture and good performance. However, in terms of the angle of view, the half angle of view at the short focus end, which is required recently, is about 45 degrees. Not.

  An object of the present invention is to provide a novel zoom lens that is suitable as an imaging lens for a digital camera, is small in size, has a large aperture and high performance, and has a wide angle of view.

The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, A fourth lens group having a positive refractive power is disposed, and an aperture stop is disposed between the second lens group and the third lens group . The lens group moves, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group changes. In the zoom lens, the first lens unit is composed of a single positive lens, the focal length of the first lens unit is f1, the thickness of the second lens unit on the optical axis is D2, and the entire system at the short focal end. Focal length: fw, conditions:
(1) 15 <f1 / fw <30
(4) 2.0 <D2 / fw <3.0
Satisfied.

  The zoom lens of the present invention has a small size, a large aperture, high performance, and a wide angle of view.

  That is, as in the embodiments described later, the wide angle of view and large aperture are as follows: half angle of view: 45 degrees or more at the short focal end, F number: about 2.0 or less, F number: about 3.0 at the long focal end. realizable.

  In addition, each of the example lenses is as small as about 9 components, and can achieve a resolving power corresponding to an image sensor with 10 to 20 million pixels.

FIG. 2 is a diagram illustrating a lens configuration of a zoom lens according to Example 1 and movement of each group accompanying zooming. FIG. 6 is a diagram illustrating a lens configuration of a zoom lens of Example 2 and movement of each group accompanying zooming. FIG. 6 is a diagram illustrating a lens configuration of a zoom lens according to Example 3 and movement of each group accompanying zooming. FIG. 6 is a diagram illustrating a lens configuration of a zoom lens according to Example 4 and movement of each group accompanying zooming. FIG. 4 is an aberration diagram at a short focal end of the zoom lens according to Example 1; FIG. 4 is an aberration diagram for the zoom lens of Example 1 at an intermediate focal length. FIG. 4 is an aberration diagram at the long focal end of the zoom lens according to Example 1; FIG. 6 is an aberration diagram at a short focal end of the zoom lens according to Example 2; 6 is an aberration diagram at an intermediate focal length of the zoom lens of Example 2. FIG. FIG. 6 is an aberration diagram at a long focal end of the zoom lens in Example 2; FIG. 10 is an aberration diagram at a short focal end of the zoom lens according to Example 3; FIG. 10 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 3; FIG. 6 is an aberration diagram at a long focal end of the zoom lens in Example 3; FIG. 10 is an aberration diagram at a short focal end of the zoom lens according to Example 4; FIG. 10 is an aberration diagram at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is an aberration diagram at a long focal end of the zoom lens in Example 4; It is a figure which shows the external appearance of a portable information terminal device. It is a figure for demonstrating the system of a portable information terminal device. It is a figure for demonstrating the electronic correction | amendment of a distortion aberration.

  Hereinafter, embodiments will be described.

1 to 4 show four examples of zoom lens embodiments. The zoom lenses in FIGS. 1 to 4 correspond to Examples 1 to 4 described later in this order.
In order to avoid complications, the same reference numerals are used in FIGS.
In these figures, the left side of the figure is the object side, and the right side is the image side.

  The zoom lens has a first lens group I to a fourth lens group IV arranged from the object side to the image side, and an aperture stop S is arranged between the second lens group II and the third lens group III. .

The refractive power of the first lens group I is positive, the refractive power of the second lens group II is negative, and the refractive power of the third lens group III and the fourth lens group IV are both positive.

  In the embodiment shown in FIGS. 1 to 4, it is assumed that the zoom lens is used for a “solid-state imaging device such as a CCD or CMOS”.

What is indicated by a symbol F on the image side of the fourth lens group IV is a representation of the cover glass and various filters of the solid-state imaging device as a transparent parallel plate that is “optically equivalent” to these.
In the embodiment described later, it is described as “filter or the like”.

  Further, the symbol IS is an image plane, which corresponds to the light receiving surface of the solid-state imaging device in these embodiments.

  When these zoom lenses are used for imaging with a silver halide photographic camera, the image plane IS matches the film plane, and in this case, the transparent parallel flat plate F may not be used.

  1 to 4, the uppermost figure shows the “lens group arrangement at the short focal end”, the middle figure shows the “lens group arrangement at the intermediate focal length”, and the lowermost figure shows the “long lens arrangement”. Lens arrangement at the focal end ”is shown.

An “arrow” indicates a displacement state of each lens group upon zooming from the short focal end to the long focal end.
As shown in FIGS. 1 to 4, in the zoom lenses of these embodiments, the first lens group I moves during zooming from the short focal end to the long focal end, and the first lens group I and the second lens are moved. Increased spacing with Group II.
Further, the distance between the second lens group II and the third lens group III decreases, and the distance between the third lens group III and the fourth lens group IV decreases or increases.

  All of the first to fourth lens groups I to IV move during zooming.

  The first lens group I is composed of one positive lens.

Also, the focal length of the first lens group: f1, the focal length of the entire system at the short focal end: fw, the condition: (1) 15 <f1 / fw <30
Satisfied.

  As in the zoom lens according to the present invention, a zoom lens including four lens groups of positive, negative, positive, and positive is configured as a so-called variator in which the third lens group bears a main zooming action.

  At the time of zooming from the short focal end to the long focal end, the first lens unit I moves while drawing a “trajectory convex toward the image side”.

  The second lens group II moves to the image side, the third lens group III moves to the object side, and the fourth lens group IV moves to the object side.

  By such movement of each lens group, the distance between the first lens group I and the second lens group II is increased, and the distance between the second lens group II and the third lens group III is decreased.

For this reason, both the magnifications (absolute values) of the second lens group II and the third lens group III are increased, but the first lens group I is composed of one lens, and the magnification is changed mainly by the third lens group III. I am doing so.
The first lens group I plays a role of slightly enhancing the zooming function of the second lens group II and preventing the F number at the long focal end from becoming too large.

  For this purpose, condition (1) is satisfied.

  Condition (1) is a condition for balancing the refractive power of the entire zoom lens system with the refractive power of the first lens group.

  When the lower limit value of the condition (1) is exceeded, the positive refractive power of the first lens group becomes relatively excessive, and the axial chromatic aberration at the long focal end can be sufficiently corrected while correcting the monochromatic aberration. It becomes difficult.

  When the upper limit is exceeded, the refractive power of the first lens group becomes relatively insufficient, the zooming function of the second lens group is weakened, and it becomes difficult to correct aberrations in the entire zoom range.

  If the first lens group is composed of a plurality of lenses, a ghost may be generated in the first lens group. However, the ghost generation in the first lens group can be reduced by using a single lens group.

In addition to the above configuration, the zoom lens according to the present invention achieves higher performance by satisfying one or more of the following conditions (2) to (6) .

(2) 2.0 <| f2 | / fw <3.0
(3) 2.5 <f3 / fw <4.0
(4) 2.0 <D2 / fw <3.0
(5) 1.5 <D3 / fw <3.0
(6) 5 <f4 / fw <10.

  In these conditions (2) to (6), “fw” is the focal length of the entire system at the short focal point. “F2, f3, f4” are focal lengths of the second to fourth lens groups, respectively.

  Furthermore, “D2 and D3” are the thicknesses on the optical axis of the second lens group and the third lens group, respectively.

  Condition (2) is a condition for balancing the refractive power of the entire zoom lens system with the refractive power of the second lens group.

  When the upper limit value of the condition (2) is exceeded, it is necessary to widen the “interval between the second lens group and the third lens group on the wide angle side” in order to realize the necessary zooming.

  Assuming a reduction in size, this leads to a reduction in the thickness of the second lens group and the third lens group, and correction of aberrations in the second and third lens groups tends to be difficult.

  When the lower limit value of the condition (2) is exceeded, the focal length of the second lens group becomes relatively short, and it becomes difficult to correct various aberrations in the second lens group.

  Condition (3) is a condition for balancing the refractive power of the entire zoom lens system with the refractive power of the third lens group.

  If the upper limit of condition (3) is exceeded, the refractive power of the third lens group will be relatively small, and it will be difficult to zoom with the third lens group, and it will be difficult to correct aberrations in the entire zoom range. easy.

  When the lower limit value of condition (3) is exceeded, the focal length of the third lens group becomes relatively short, and correction of various aberrations in the third lens group tends to be difficult.

  Condition (4) is a condition that regulates an appropriate range of the “thickness on the optical axis” of the second lens group with respect to the focal length of the entire zoom lens system.

  When the upper limit value of the condition (4) is exceeded, the second lens group becomes relatively thick when it is assumed to be downsized, and it becomes necessary to compensate for the thickened portion in other parts of the lens system.

  That is, it is necessary to shorten the “second and third lens group spacing” or to reduce the “thickness on the optical axis” of the third lens group, and it is difficult to correct aberrations in the entire zoom range. .

  When the lower limit of condition (4) is exceeded, the thickness of the second lens group becomes relatively thin, and correction of various aberrations in the second lens group tends to be difficult.

  Condition (5) is a condition for regulating an appropriate range of the “thickness on the optical axis” of the third lens group with respect to the focal length of the entire zoom lens system.

  When the upper limit value of the condition (5) is exceeded, when the size reduction is assumed, the third lens group becomes relatively thick, and it becomes necessary to compensate for the thickened portion in other parts of the lens system.

  That is, it is necessary to shorten the “second and third lens group spacing” or to reduce the “thickness on the optical axis” of the second lens group, and it is difficult to correct aberrations in the entire zoom range. .

  When the lower limit value of the condition (5) is exceeded, the thickness on the optical axis of the third lens group becomes relatively thin, and correction of various aberrations in the third lens group tends to be difficult.

  By satisfying the conditions (4) and (5), downsizing can be promoted while maintaining high performance.

  Condition (6) is a condition that regulates an appropriate range of the focal length of the fourth lens group with respect to the focal length of the entire zoom lens system.

  When the upper limit value of the condition (6) is exceeded, the positive refractive power of the fourth lens group is relatively increased, the exit pupil is close to the image plane, and it is difficult to ensure high telecentricity.

  If the lower limit of condition (6) is exceeded, it will be difficult to correct aberrations occurring in the fourth lens group with a simple configuration.

  Preferably, the fourth lens group is composed of a single positive lens as in Examples 1 to 4.

  It is preferable that the “aperture stop” disposed between the second lens group and the third lens group “moves independently” upon zooming from the short focal end to the long focal end.

  Since the aperture stop is on the object side of the third lens group at the short focal end, the lens group on the object side of the aperture stop can be made smaller.

  In addition, aberration correction can be performed with a simple lens group on the object side of the aperture stop.

  As described above, when the aperture stop is moved independently during zooming, higher performance can be realized by satisfying the following condition (7).

  (7) 0.15 <TLs3_w / TL2s_w <0.40.

  In condition (7), “TLs3_w” is the distance between the aperture stop and the third lens group at the short focal end, and “TL2s_w” is the distance between the second lens group and the aperture stop at the short focal end.

  When the lower limit of condition (7) is exceeded, the distance between the second lens group and the aperture stop becomes relatively large.

  For this reason, the “off-axis ray passing through the second lens group” at the short focal point becomes high, and correction of off-axis aberrations in the second lens group tends to be difficult, and the second lens group tends to be large.

  When the upper limit of condition (7) is exceeded, the distance between the third lens group and the aperture stop becomes relatively large.

  For this reason, “off-axis light beam passing through the third lens group” becomes high at the short focal end, and it becomes difficult to correct aberrations in the third lens group, and the third lens group tends to be large.

  When the condition (7) is satisfied, the zoom lens can be further reduced in size and performance.

  In addition, when changing the magnification from the short focus end to the long focus end, the movement of each lens group is preferably as follows.

  That is, the second lens group moves to the image side, the third lens group moves to the object side, and the fourth lens group moves to the object side so that the first lens group draws a trajectory convex toward the image side. Is good.

It is preferable that “the distance between the third lens group and the fourth lens group is increased”.
In this way, the distance between the third lens group and the fourth lens group is ensured at the long focal end. Therefore, in this case, it is preferable to perform focusing with the fourth lens group.

  When it is necessary to reduce the amount of light reaching the image plane, the aperture stop may be reduced in diameter.

  However, it is preferable to reduce the amount of light by inserting an ND filter or the like without greatly changing the aperture diameter, because a reduction in resolution due to a diffraction phenomenon can be prevented.

In order to further improve the performance, the refractive index: Nd and Abbe number: νd of the material of one positive lens constituting the first lens group are as follows:
(8) 1.45 <Nd <1.65, 50 <νd <85
Good to be satisfied.
When the material of one positive lens constituting the first lens group satisfies the condition (8), sufficient aberration correction can be realized.

  Further, as a glass material satisfying the condition (8), there is “low-cost glass type (S-BSL7 [OHARA] product name)” and the like, and the cost reduction of the zoom lens can be expected.

Before giving a specific example of a zoom lens, an embodiment of a portable information terminal device will be described with reference to FIGS.
As shown in FIG. 18, the “system configuration” of the portable information terminal device shown in FIG. 17 includes a photographing lens 1 that is a “zoom lens” and a light receiving element 13 that is a “solid-state imaging device”.

  An image of the photographing object formed by the photographing lens 1 is configured to be read by the light receiving element 13.

  The output from the light receiving element 13 is processed by the signal processing device 14 under the control of the central processing unit 11 and converted into digital information.

The image converted into digital information is displayed on the liquid crystal monitor 7 and stored in the semiconductor memory 15 or used for communication to the outside by the communication card 16 or the like.
The portion excluding this communication function constitutes a “camera”.

  As the photographing lens 1, any one of the zoom lenses according to any one of claims 1 to 9, specifically, any of the zoom lenses of Examples 1 to 4 to be described later can be used.

  The “monitored image” can be displayed on the liquid crystal monitor 7 or an image recorded in the semiconductor memory 15 can be displayed.

The taking lens 1 is in the “collapsed state” as shown in FIG. 17A when the camera is carried, and the lens barrel is extended from the housing 5 when the power is turned on by operating the power switch 6.
In a state where the lens barrel is extended, each group of zoom lenses is “for example, an arrangement of short focal ends” inside the lens barrel.
By operating the zoom lever 10, the arrangement of each group changes, and zooming to the long focal end can be performed.
At this time, the viewfinder 2 also zooms in conjunction with the change in the angle of view of the taking lens 1.

  Focusing is performed by “half-pressing” the shutter button 4.

Focusing can be performed by moving the fourth lens unit as in the example lens, but can also be performed by “moving the light receiving element”.
When the shutter button 4 is further pressed, shooting is performed, and thereafter the above processing is performed.

When the image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside using the communication card 16 or the like, the operation button 8 is operated.
The semiconductor memory 15 and the communication card 16 are inserted into dedicated or general-purpose slots 9 for use.

When the photographic lens is in the “collapsed state”, the lens groups of the zoom lens do not necessarily have to be arranged on the optical axis.
For example, a mechanism in which the third lens group and / or the fourth lens group is retracted from the optical axis and “stored in parallel with other lens groups” can be employed.

By doing so, it is possible to further reduce the thickness of the portable information terminal device.
In this case, since the third lens group is thicker in the optical axis direction than the fourth lens group, retracting the third lens group from the optical axis can greatly contribute to the thinning of the retracted state.

  Using the zoom lens shown in Embodiments 1 to 4, it is possible to realize a portable information terminal device having a high image quality and a small camera function using a light receiving element of 10 million to 20 million pixel class.

  Hereinafter, four specific examples of the zoom lens will be described.

  These Examples 1 to 4 have a four lens group configuration with positive, negative, positive, and positive power distribution, and cross-sectional views are shown in FIGS.

  In all the examples, the lens materials other than the fourth lens group are all optical glass. Since one positive lens constituting the fourth lens group does not have an “influence on image quality due to surface accuracy”, a resin lens may be used instead of the optical glass lens.

  The meanings of the symbols in the examples 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
ν _d : Abbe number
K: Aspherical conical constant
H: Radius of each lens surface
φ: Effective diameter of each lens surface
A4: Fourth-order aspheric coefficient
A6: 6th-order aspheric coefficient
A8: 8th-order aspheric coefficient
A10: 10th-order aspheric coefficient
“Aspherical surface” is a well-known equation using the reciprocal of the paraxial radius of curvature (paraxial curvature): C, the height from the optical axis: H, the conic constant: K, and the aspheric coefficient: A4 to A10. It is represented by

X = CH ² / {1 + √ (1− (1 + K) C ² H ² )} + A4 · H ⁴ + A6 · H ⁶
+ A8 · H ⁸ + A10 · H ¹⁰ .

"Example 1"
The zoom lens of Example 1 is shown in FIG.
Table 1 shows data of the zoom lens of Example 1.

"Variable amount"
Variable amounts of data are shown in Table 2.

  In Table 2, “Wide” is “short focal end”, “Mean” is “intermediate focal length”, and “Tele” is “long focal end”. The same applies to the following other embodiments.

"Aspherical data"
Table 3 shows the aspherical data. An aspherical surface is a surface marked with “*” in the above data. The same applies to Examples 2 to 4 below.

"Parameter values for each condition"
Table 4 shows the parameter values for each condition.

"Example 2"
The zoom lens of Example 2 is shown in FIG.
Table 5 shows data of the zoom lens of Example 2.

"Variable amount"
The variable amount of data is shown in Table 6.

"Aspherical data"
Table 7 shows the aspherical data.

"Parameter values for each condition"
Table 8 shows the parameter values for each condition.

"Example 3"
The zoom lens of Example 3 is the one shown in FIG.
Table 9 shows data of the zoom lens of Example 2.

"Variable amount"
Variable amounts of data are shown in Table 10.

"Aspherical data"
Table 11 shows the aspherical data.

"Parameter values for each condition"
Table 12 shows the parameter values for each condition.

Example 4
The zoom lens of Example 4 is the one shown in FIG.
Table 13 shows data of the zoom lens of Example 4.

"Variable amount"
The variable amount of data is shown in Table 14.

"Aspherical data"
Table 15 shows the aspheric data.

"Parameter values for each condition"
Table 16 shows the parameter values for each condition.

  5 to 7 sequentially show aberration curves at the short focal end, the intermediate focal length, and the long focal end of the zoom lens according to the first embodiment.

  FIGS. 8 to 10 sequentially show aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end of the zoom lens according to the second embodiment.

  FIGS. 11 to 13 sequentially show aberration curves at the short focal end, the intermediate focal length, and the long focal end of the zoom lens according to the third embodiment.

  FIGS. 14 to 16 sequentially show aberration curve diagrams at the short focal end, the intermediate focal length, and the long focal end of the zoom lens according to the fourth embodiment.

In these aberration curve diagrams, the broken line in the “spherical aberration” diagram indicates the sine condition, the solid line in the astigmatism diagram indicates sagittal, and the broken line indicates meridional.
“D” indicates an aberration curve with respect to the d-line, and “g” indicates an aberration curve with respect to the g-line.

  “Y ′” is the maximum image height.

  In each example, the value at both ends of the horizontal axis in spherical aberration is “± 0.1”, and the value at both ends of the horizontal axis in astigmatism is “± 0.1”.

  Further, the values at both ends of the horizontal axis in the distortion aberration are “± 10%”, and the values at both ends of the vertical axis in the coma aberration diagram are “± 0.01”.

As is clear from these aberration curve diagrams, the zoom lens of each embodiment has sufficiently corrected aberration, and can sufficiently cope with a solid-state imaging device having 10 to 20 million pixels.
As is clear from these examples, the zoom lens of the present invention can ensure a very good image performance while achieving a sufficient size reduction.
In all of Examples 1 to 4, the “back focus at the short focal end” is 1.0 mm.

  In Examples 1 to 4, the occurrence of distortion is suppressed near the intermediate focal length and at the long focal end, but “barrel distortion on a rectangular light receiving element” occurs at the short focal end.

  Therefore, electronic processing is performed on the data that has been computerized by the solid-state imaging device to correct “distortion aberration in the formed image”.

For this reason, the effective imaging range in the solid-state imaging device is “barrel shape at the short focal end”, and “substantially rectangular shape” at the intermediate focal length and long focal end.
Then, the effective imaging range at the short focal end is electronically converted by image processing into rectangular image information with reduced distortion.

  For this reason, the image height at the short focal end is 4.1 mm or 4.3 mm, and the image height at the intermediate focal length or the long focal end is 4.8 mm.

In FIG. 19, reference numeral Im <b> 1 indicates “the shape of the light receiving surface of the solid-state imaging device”, which has a rectangular shape.
A circle IC1 circumscribing the light receiving surface shape Im1 is an image circle that covers the light receiving surface shape Im1, and is an “imaging range” at the long focal end / intermediate focal length.

In FIG. 19, the reference numeral 1m2 indicates “the shape of the image plane at the short focal end” in an explanatory manner.
Since “intentionally negative distortion” is allowed in the vicinity of the short focal end, the image plane shape Im2 is a “barrel shape”.
Note that the negative distortion in FIG. 19 is depicted as “slightly exaggerated”.

  Such a “barrel-shaped image surface shape” is electronically corrected to a shape that matches the light receiving surface shape Im1.

Distortion can be corrected electronically as described above.
Therefore, if distortion is allowed to occur within a range in which electronic correction is possible, the conditions for the degree of freedom in correcting other aberrations and the zoom ratio can be relaxed, and a large zoom ratio can be realized.
In addition, as described above, the image circle at the intermediate focal length and the short focal end can be made small, so that there is a great effect in widening the angle.

  In Examples 1 to 4, the zoom ratio is “about 3.4 to 3.8 times”, but a sufficiently high zoom ratio can be realized by combining with an electronic zoom.

I First lens group
II Second lens group
III Third lens group
IV Fourth lens group
S Aperture stop

JP 2004-199000 A JP 2001-242379 A JP 2002-72087 A JP 2002-196241 A

Claims (16)

In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged, and an aperture stop is disposed between the second lens group and the third lens group,
Upon zooming from the short focal end to the long focal end, the first lens group moves, the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group decreases. In the zoom lens in which the distance between the third lens group and the fourth lens group changes,
The first lens group is composed of one positive lens,
Focal length of the first lens group: f1, thickness on the optical axis of the second lens group: D2, focal length of the entire system at the short focal end: fw, conditions:
(1) 15 <f1 / fw <30
(4) 2.0 <D2 / fw <3.0
A zoom lens characterized by satisfying The zoom lens according to claim 1.
Thickness on the optical axis of the third lens group: D3, focal length of the entire system at the short focal end: fw, conditions:
(5) 1.5 <D3 / fw <3.0
A zoom lens characterized by satisfying In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged, and an aperture stop is disposed between the second lens group and the third lens group,
Upon zooming from the short focal end to the long focal end, the first lens group moves, the distance between the first lens group and the second lens group increases, and the distance between the second lens group and the third lens group decreases. In the zoom lens in which the distance between the third lens group and the fourth lens group changes,
The first lens group is composed of one positive lens,
Focal length of the first lens group: f1, thickness of the third lens group on the optical axis: D3, focal length of the entire system at the short focal end: fw, conditions:
(1) 15 <f1 / fw <30
(5) 1.5 <D3 / fw <3.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 3,
The focal length of the second lens group: f2, the focal length of the entire system at the short focal end: fw, the condition:
(2) 2.0 <| f2 | / fw <3.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 4,
The focal length of the third lens group: f3, the focal length of the entire system at the short focal end: fw, the condition:
(3) 2.5 <f3 / fw <4.0
A zoom lens characterized by satisfying In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged, and an aperture stop is disposed between the second lens group and the third lens group,
Upon zooming from the short focal end to the long focal end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group and the fourth lens group decrease. In zoom lenses where the distance between lens groups changes,
The first lens group is composed of one positive lens,
Focal length of the first lens group: f1, focal length of the second lens group: f2, focal length of the third lens group: f3, focal length of the entire system at the short focal end: fw, conditions:
(1) 15 <f1 / fw <30
(2) 2.0 <| f2 | / fw <3.0
(3) 2.5 <f3 / fw <4.0
A zoom lens characterized by satisfying The zoom lens according to claim 6.
Thickness on optical axis of second lens group: D2, focal length of entire system at short focal end: fw, conditions:
(4) 2.0 <D2 / fw <3.0
A zoom lens characterized by satisfying In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged, and an aperture stop is disposed between the second lens group and the third lens group,
Upon zooming from the short focal end to the long focal end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group and the fourth lens group decrease. In zoom lenses where the distance between lens groups changes,
The first lens group is composed of one positive lens,
Focal length of the first lens group: f1, focal length of the second lens group: f2, thickness of the second lens group on the optical axis: D2, focal length of the entire system at the short focal end: fw
(1) 15 <f1 / fw <30
(2) 2.0 <| f2 | / fw <3.0
(4) 2.0 <D2 / fw <3.0
A zoom lens characterized by satisfying In order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged, and an aperture stop is disposed between the second lens group and the third lens group,
Upon zooming from the short focal end to the long focal end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group and the fourth lens group decrease. In zoom lenses where the distance between lens groups changes,
The first lens group is composed of one positive lens,
The focal length of the first lens group: f1, the focal length of the third lens group: f3, the thickness of the second lens group on the optical axis: D2, the focal length of the entire system at the short focal end: fw, the condition:
(1) 15 <f1 / fw <30
(3) 2.5 <f3 / fw <4.0
(4) 2.0 <D2 / fw <3.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 6 to 9,
Thickness on the optical axis of the third lens group: D3, focal length of the entire system at the short focal end: fw, conditions:
(5) 1.5 <D3 / fw <3.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 10,
Focal length of the fourth lens group: f4, focal length of the entire system at the short focal end: fw, conditions:
(6) 5 <f4 / fw <10
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 11,
A zoom lens, wherein an aperture stop moves independently upon zooming from a short focal end to a long focal end. The zoom lens according to claim 12, wherein
The distance between the aperture stop and the third lens group at the short focus end: TLs3_w, and the distance between the second lens group and the stop at the short focus end: TL2s_w:
(7) 0.15 <TLs3_w / TL2s_w <0.40
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 13,
Used in an information device that reads an image from a zoom lens with a solid-state image sensor,
A zoom lens characterized in that the distortion is allowed in a range that can be corrected by electronic processing of data computerized by the solid-state imaging device. 15. A camera comprising the zoom lens according to claim 1 as a photographing optical system. 15. A portable information terminal device comprising the zoom lens according to claim 1 as a photographing optical system of a camera function unit.

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