JP4907169B2 - Zoom lens, camera device, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens that can be used for a digital camera, a portable information terminal device, a video camera, a silver salt camera, and the like, a camera device using the zoom lens, and a portable information terminal device.

  Currently, there is a strong demand for digital cameras included in camera devices such as higher image quality, smaller size, wider angle of view, and larger aperture. In addition, it is expected that the distortion aberration of the taking lens system used for the zoom lens is as small as possible. In the future, it will be necessary to develop technologies to meet these demands. The photographing lens is required to be a zoom lens and to have a high image quality, a small size, a wide angle of view, and a large aperture in order to cope with a light receiving element exceeding 5 million pixels.

  As a zoom lens that can be used in digital cameras and other various camera devices, technical development has been carried out in order to meet the above requirements. For example, in order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a first lens group having a positive focal length. A zoom lens having four lens groups and having a stop on the object side of the third lens group is known. Among such zoom lenses, zoom lenses having three cemented lenses in a third lens group are known. (For example, see Patent Document 1, Patent Document 2, and Patent Document 3).

  However, in the invention described in Patent Document 1, the F number at the short focal end is limited to 2.5 and cannot be made brighter than that. In the inventions described in Patent Document 2 and Patent Document 3, the half angle of view cannot be set to 38 ° or more.

Further, in order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a first lens group having a positive focal length. A zoom lens having four lens groups and having a stop on the object side of the third lens group, a zoom lens having three cemented lenses of a positive lens, a negative lens, and a positive lens in the third lens group is known. (For example, see Patent Document 4).
However, in the invention described in Patent Document 4, since the third lens group is composed only of cemented lenses, the half angle of view cannot be set to 38 ° or more.

JP 2004-286811 A JP 2001-305427 A Japanese Patent Laid-Open No. 11-316340 JP 2005-308998 A

  The present invention has been made in view of the above-mentioned problems of the prior art. High performance, that is, aberration is corrected well, a wide angle of view with a half angle of view of 38 ° or more, and an F number at the short focal point is 2. An object of the present invention is to provide a zoom lens that is sufficiently small while being 5 or less.

A second aspect of the invention is to reduce the size of the zoom lens according to the first aspect of the present invention while achieving high performance.
A third aspect of the invention is to improve the performance of the zoom lens of the first aspect.
The invention according to claim 4 is to further improve the performance of the zoom lens according to claim 3.
A fifth aspect of the present invention aims to reduce the size of the zoom lens according to the first aspect of the invention while having high performance.
A sixth aspect of the present invention aims to reduce the influence of manufacturing errors and the like on the zoom lens of the first aspect.
The object of the seventh aspect of the invention is to improve the performance of the zoom lens of the first aspect.
The invention according to claim 8 is to improve the performance of the zoom lens according to claim 1.
The invention according to claim 9 is to further reduce the size of the zoom lens according to claim 1.

The invention described in claim 10 is a high-performance zoom lens that has a wide angle of view with a half angle of view of 38 ° or more and an F number at the short focal end of 2.5 or less, but is sufficiently small. The purpose of this is to provide a small and high-quality camera device.
An object of the present invention is to provide a camera device capable of having a function of using a captured image as digital information.

  According to a twelfth aspect of the present invention, a zoom lens having a high performance, a wide angle of view with a half angle of view of 38 ° or more, and an F number at a short focal point of 2.5 or less, but a sufficiently small zoom lens is provided. It is intended to provide a small and high-quality portable information terminal device used as

According to the first aspect of the present invention, the first lens group having a positive focal length, the second lens group having a negative focal length, and the positive focal length in order from the object side. a third lens group consists of a fourth lens group having a positive focal length, has a diaphragm on the object side of the third lens group, upon zooming from the short focal end to the long focal end, the In a zoom lens having a zoom lens in which the distance between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is decreased, and the distance between the third lens group and the fourth lens group is increased. The third lens group includes, in order from the object side , a cemented lens including a positive lens, a negative lens, and a positive lens, a positive lens on the object side from the cemented lens, and a negative lens on the image side from the cemented lens. Main features.

According to a second aspect of the present invention, in the zoom lens according to the first aspect, the radius of curvature of the negative lens constituting the cemented lens in the third lens group where the negative power is strong is Rn, and the maximum image height is Y ′. When
0.8 <Rn / Y ′ <2.0
It satisfies the following conditional expression.

  According to a third aspect of the present invention, in the zoom lens according to the first or second aspect, the negative lens constituting the cemented lens in the third lens group is a biconcave lens.

According to a fourth aspect of the present invention, in the zoom lens according to the third aspect, the radius of curvature of the object side surface of the negative lens constituting the cemented lens in the third lens group is R2, and the image side surface of the cemented lens in the third lens group. When the radius of curvature of R3 is R3,
1.0 <| R2 / R3 | <10.0
It satisfies the following conditional expression.

According to a fifth aspect of the present invention, in the zoom lens according to any one of the first to fourth aspects, the thickness of the negative lens constituting the cemented lens in the third lens group is dn, and the thickness of the third lens group cemented lens is When the thickness is ds,
0.1 <dn / ds <0.4
It satisfies the following conditional expression.

According to a sixth aspect of the present invention, in the zoom lens according to any one of the first to fifth aspects, the cemented lens in the third lens group comprises only a spherical lens.
A seventh aspect of the present invention is the zoom lens according to any one of the first to sixth aspects, further comprising an aspherical lens having a positive focal length on the most object side of the third lens group.
According to an eighth aspect of the present invention, in the zoom lens according to any one of the first to seventh aspects, an aspherical lens having a negative focal length is provided on the most image side of the third lens group.

The invention according to claim 9 is the zoom lens according to any one of claims 1 to 8, wherein the thickness of the third lens group is d3, and the thickness of the cemented lens in the third lens group is ds.
0.3 <ds / d3 <0.9
It satisfies the following conditional expression.

According to a tenth aspect of the present invention, there is provided a camera device for photographing a subject image and recording a photographed image, wherein the zoom lens according to any one of the first to ninth aspects is provided.
The invention described in claim 11 is the camera apparatus described in claim 10, characterized in that it has a function of using a captured image as digital information.

  According to a twelfth aspect of the present invention, there is provided a portable information terminal device capable of photographing a subject image and recording a photographed image, comprising the zoom lens according to any one of the first to ninth aspects.

  According to the first aspect of the present invention, the zoom lens has a high performance, a wide angle of view with a half angle of view of 38 ° or more, and a sufficiently small size while having an F number of 2.5 or less at the short focal end. Can be provided. By adopting this zoom lens in a digital camera, a small digital camera with high image quality can be realized.

According to the second aspect of the present invention, it is possible to obtain a small zoom lens with high performance, and to realize a small camera with high image quality by adopting this zoom lens in a camera. Can do.
According to the third, fourth, seventh and eighth aspects of the invention, a higher-performance zoom lens can be provided, and a camera with higher image quality can be realized by using the zoom lens in the camera. it can.
According to the fifth and ninth aspects of the invention, it is possible to obtain a small zoom lens with high performance, and by adopting this zoom lens in the camera, a further small camera can be realized.
According to the sixth aspect of the present invention, it is possible to provide a zoom lens that is less affected by manufacturing errors and the like. By adopting this zoom lens in a camera, a more stable camera can be realized.

According to the invention of claim 10, the zoom lens has a high performance, a wide angle of view with a half angle of view of 38 ° or more, and a sufficiently small size while the F number at the short focal point is 2.5 or less. A small, high-quality camera using this can be provided. Users can take high-quality images with a highly portable camera.
According to the eleventh aspect of the invention, a zoom lens that has high performance, a wide angle of view with a half angle of view of 38 ° or more, and an F number at the short focal point of 2.5 or less but a sufficiently small size is used. In addition, since a small and high-quality digital camera can be provided, the user can take a high-quality image with a camera having excellent portability and handle the taken image as digital information.

  According to the invention of claim 12, there is provided a zoom lens having high performance, a wide angle of view with a half angle of view of 38 ° or more, and a sufficiently small size while having an F number of 2.5 or less at the short focal end. It is possible to provide a small-sized and high-quality portable information terminal device used. The user can take a high-quality image with the portable information terminal device.

Embodiments of a zoom lens, a camera device, and a portable information terminal device according to the present invention will be described below with reference to the drawings. FIGS. 1 to 5 are optical arrangement diagrams showing first to fifth embodiments of the zoom lens according to the present invention, respectively.
The zoom lens according to the present invention includes a first lens group G1 having a positive focal length and a negative focal length in order from the object side (left side in FIGS. 1 to 5), as shown in FIGS. A second lens group G2 having a positive focal length, a fourth lens group G4 having a positive focal length, and a stop on the object side of the third lens group G3. It becomes. The position of each lens group shown in FIGS. 1 to 5 is the short focal end position. Upon zooming from the short focal end to the long focal end, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens The distance between the group G3 and the fourth lens group G4 is increased. The curves shown in the lower portions of FIGS. 1 to 5 indicate the movement trajectories of the lens groups and the diaphragm during zooming.

  The first lens group G1 includes a first lens L1 and a second lens L2. The second lens group G2 includes a third lens L3, a fourth lens L4, and a fifth lens L5. The third lens group G3 includes a fifth lens L6, a seventh lens L7, an eighth lens L8, a ninth lens L9, and a tenth lens L10. The fourth lens group G4 includes an eleventh lens L11. A filter composed of a parallel plate is disposed between the eleventh lens L11 and the image plane.

  Each of the embodiments shown in FIGS. 1 to 5 has the following characteristics. The third lens group G3 includes a cemented lens including a positive lens, a negative lens, and a positive lens, and at least one lens. In each embodiment, the seventh lens L7 constituting the third lens group G3 is positive, the eighth lens L8 is negative, the ninth lens L9 is positive, and these three lenses are cemented. The sixth lens L6 located closest to the object side and constituting the third lens group G3 is positive, and the tenth lens L10 located closest to the image side is negative.

The zoom lens according to each of the above examples satisfies the following conditional expression.
0.8 <Rn / Y ′ <2.0
Here, Rn is the radius of curvature of the negative lens (eighth lens L8) constituting the cemented lens in the third lens group G3, and Y 'is the maximum image height.
The negative lens (eighth lens L8) constituting the cemented lens in the third lens group G3 is a biconcave lens.

The zoom lens according to each of the above examples also satisfies the following conditional expression.
1.0 <| R2 / R3 | <10.0
Here, R2 is the radius of curvature of the object side surface of the negative lens (eighth lens L8) constituting the cemented lens in the third lens group G3, and R3 is the image side surface constituting the cemented lens in the third lens group G3. This is the radius of curvature of (the image side surface of the ninth lens L9).

Further, the zoom lens according to each of the above examples satisfies the following conditional expression.
0.1 <dn / ds <0.4
Here, dn is the thickness of the negative lens (eighth lens L8) constituting the cemented lens in the third lens group G3, and ds is the cemented lens (seventh lens L7, eighth lens) in the third lens group G3. The thickness of the lens L8 and the ninth lens L9).

The cemented lens (seventh lens L7, eighth lens L8, and ninth lens L9) in the third lens group G3 includes only a spherical lens.
The lens (sixth lens L6) disposed on the most object side of the third lens group G3 is an aspheric lens.
Furthermore, the lens (tenth lens L10) arranged on the most image side of the third lens group G3 is also an aspheric lens.

The zoom lens according to each of the above examples satisfies the following conditional expression.
0.3 <ds / d3 <0.9
Here, d3 is the thickness of the third lens group G3, and ds is the thickness of the cemented lens (seventh lens L7, eighth lens L8, and ninth lens L9).

  The zoom lens according to the present invention employs a zoom type with four lens groups preceded by positive power, and the first lens group G1 and the second lens group G2 during zooming from the short focal end to the long focal end. The distance between the second lens group G2 and the third lens group G3 is decreased, and the distance between the third lens group G3 and the fourth lens group G4 is increased. Efficient scaling is achieved for the amount of movement. In the case of such a zoom type, it is possible to perform focusing by extending all the lens groups. However, in the illustrated embodiment, focusing is performed by the fourth lens group G4. This is desirable because the moving mechanism becomes simple.

  In order to realize a zoom lens that has few aberrations from the short focal point to the long focal point and has a high resolving power, it is necessary to suppress aberration fluctuations due to zooming. In particular, it is necessary that the third lens group G3, which performs the zooming action or the two actions of zooming and image plane correction, be satisfactorily corrected over the entire zooming range. Therefore, the configuration of the third lens group is important.

  In the zoom lens according to the present invention, the third lens group G3 includes three lenses including a positive lens, a negative lens, and a positive lens (seventh lens L7, eighth lens L8, and ninth lens L9) in order from the object side. It was set as the structure which has the cemented lens which joined. Since it is a joint surface, the eccentricity during assembly can be kept small, so that the radius of curvature can be reduced and the degree of freedom in design increases. In order to provide two cemented surfaces, it is conceivable to use two pairs of cemented lenses. However, there is a problem that the optical axes of the cemented lenses are shifted due to decentering during assembly. On the other hand, if a cemented lens composed of three lenses is used as described above, the assembly eccentricity generated on the two cemented surfaces can be kept small. In order to make a wide lens with a half angle of view of 38 ° or more and a bright lens with an F number at the short focal length of 2.5 or less, both the on-axis aberration and off-axis aberration must be corrected with the cemented lens alone. Therefore, it is necessary to configure the third lens group G3 with a cemented lens and at least one lens. In the third lens group G3, it is possible to correct spherical aberration, coma, etc. by disposing the lens on the object side of the cemented lens, and by disposing the lens on the image side of the cemented lens, Since it is possible to correct curvature and the like, it is possible to correct aberrations that cannot be corrected only with a cemented lens. Since the third lens group G3 has a positive focal length as a whole, the Abbe number of the negative lens L8 constituting the cemented lens of the third lens group G3 is preferably smaller than the Abbe number of the positive lens constituting the cemented lens. .

It is desirable to satisfy the following conditional expression for miniaturization while being high performance.
0.8 <Rn / Y ′ <2.0 (1)
Here, Rn is the radius of curvature of the negative lens L8 constituting the cemented lens of the third lens group G3, and Y 'is the maximum image height. If the upper limit of Expression (1) is exceeded, the power of the negative lens (eighth lens L8) of the third lens group cannot be increased, and the tilt of the image plane due to the positive lens of the third lens group G3 is corrected. If the lower limit of expression (1) is exceeded, the thickness of the positive lens in contact with the strong negative power surface of the negative lens (eighth lens L8) constituting the cemented lens of the third lens group G3 Becomes thicker and hinders miniaturization. More desirably, the following conditional expression should be satisfied.
0.9 <Rn / Y ′ <1.7 (1 ′)

  In order to achieve higher performance, it is desirable that the negative lens (eighth lens L8) constituting the cemented lens of the third lens group G3 is a biconcave lens. Since both surfaces of the negative lens (eighth lens L8) have negative power, coma aberration and the like can be corrected in a well-balanced manner while correcting image plane tilt due to the positive lens.

For higher performance, it is desirable to satisfy the following conditional expression.
1.0 <| R2 / R3 | <10.0 (2)
Here, R2 is the radius of curvature of the object side surface of the negative lens (eighth lens L8) constituting the cemented lens of the third lens group G3, and R3 is the negative lens (first lens constituting the cemented lens of the third lens group G3). 8 lens L8) radius of curvature of the image side surface. When the upper limit value and lower limit value of Expression (2) are exceeded, it is difficult to correct coma aberration and the like in a balanced manner. More desirably, the following conditional expression should be satisfied.
1.5 <| R2 / R3 | <9.5 (2 ′)

For further miniaturization, it is desirable to satisfy the following conditional expression.
0.1 <dn / ds <0.4 (3)
Here, dn is the thickness of the negative lens (eighth lens L8) constituting the cemented lens of the third lens group G3, and ds is the thickness of the cemented lens of the third lens group G3. If the upper limit of equation (3) is exceeded, the thickness of the positive lens becomes thin and the radius of curvature of the cemented surface cannot be reduced, so coma aberration and the like can be corrected while correcting the image surface tilt due to the positive lens. It becomes difficult to correct. If the lower limit of Expression (3) is exceeded, the thickness of the positive lens becomes thick, which hinders downsizing. More desirably, the following conditional expression should be satisfied.
0.12 <dn / ds <0.3 (3 ′)

  In order to reduce the adverse effect due to the manufacturing error of the lens, it is desirable that the cemented lens of the third lens group G3 is composed of only a spherical lens. Aspherical lenses tend to be greatly affected by manufacturing errors and assembly errors and need to be adjusted during assembly. Therefore, it is desirable not to use aspherical lenses as the lenses constituting the cemented lens.

  In order to achieve higher performance, it is desirable to use an aspherical lens having a positive focal length as the lens (sixth lens L6) arranged on the most object side of the third lens group G3. At the position of the lens (sixth lens L6) having the positive focal length closest to the object side of the third lens group G3, the luminous flux becomes the thickest, so that an aspherical effect is obtained for correcting spherical aberration and coma aberration. . More preferably, a positive lens having a convex object side surface is used, and the object side surface is preferably an aspherical surface.

In order to achieve higher performance, it is desirable that the lens (tenth lens L10) disposed on the most image side of the third lens group G3 is an aspherical lens. By arranging the aspherical lens on the most image side of the third lens group G3, the on-axis light beam and the off-axis light beam are separated from each other, so that the effect of the aspheric surface can be obtained in the image surface correction. More preferably, the image side is preferably an aspherical surface.
In order to achieve further downsizing, it is desirable to satisfy the following conditional expression.
0.3 <ds / d3 <0.9 (4)
Here, d3 is the thickness of the third lens group G3, and ds is the thickness of the cemented lens of the third lens group G3. When the upper limit of Expression (4) is exceeded, the ratio of the thickness of the cemented lens to the thickness of the third lens group G3 increases, and the degree of freedom in designing lenses other than the cemented lens is lost, making it difficult to correct aberrations. When the lower limit of Expression (4) is exceeded, the third lens group G3 is prevented from being downsized. More desirably, the following conditional expression should be satisfied.
0.4 <ds / d3 <0.8 (4 ′)

Next, each example of the zoom lens according to the present invention will be described together with numerical values. The meanings of symbols in each embodiment are as follows.
f: focal length of all lens system F: F number ω: half angle of view R: radius of curvature D: surface spacing Nd: refractive index νd: Abbe number K: aspherical conical constant A4: fourth-order aspherical coefficient A6: 6th-order aspheric coefficient A8: 8th-order aspheric coefficient A10: 10th-order aspheric coefficient

However, the aspherical surface used here is defined by the following formula 1 where C is the reciprocal of the paraxial radius of curvature (paraxial curvature) and H is the height from the optical axis.
(Formula 1)

FIG. 1 is an optical arrangement diagram showing Example 1 of the zoom lens according to the present invention, and Numerical Example 1 is shown in Table 1.

In Table 1, the fifth surface, the eleventh surface, the eighteenth surface, and the nineteenth surface marked with “*” are aspherical surfaces, and the parameters according to the above-mentioned formula 1 in each aspherical surface are as follows.

Table 2 shows the focal length f (mm) at the wide-angle end (Wide), the intermediate focal position (Mean), the telephoto end (Tele), and the distance between the surfaces whose numerical values change according to the zooming operation. Showing change. In Table 2, A is the change in the distance between the first lens group G1 and the second lens group G2, B is the change in the distance between the second lens group G2 and the diaphragm, C is the change in the distance between the diaphragm and the third lens group G3, and D is the first. The change in the distance between the third lens group G3 and the fourth lens group G4 is shown.

Numerical values corresponding to the conditional expressions in the numerical example 1 are as follows. Both are within the range of each conditional expression.
Conditional expression numerical value Rn / Y ′ = 1.064
| R2 / R3 | = 1.914
dn / ds = 0.155
ds / d3 = 0.573

FIG. 2 is an optical arrangement diagram showing Example 2 of the zoom lens according to the present invention. Numerical Example 2 is shown in Table 3.

In Table 3, the fifth surface, the eleventh surface, the eighteenth surface, and the nineteenth surface marked with “*” are aspherical surfaces, and the parameters according to the above-mentioned formula 1 in each aspherical surface are as follows.

Table 4 shows the focal length f (mm) at the wide-angle end (Wide), the intermediate focal position (Mean), the telephoto end (Tele), and the distance between the surfaces whose numerical values change according to the zooming operation. Showing change. In Table 4, A is a change in the distance between the first lens group G1 and the second lens group G2, B is a change in the distance between the second lens group G2 and the stop, C is a change in the distance between the stop and the third lens group G3, and D is the first change. The change in the distance between the third lens group G3 and the fourth lens group G4 is shown.

Numerical values corresponding to the conditional expressions in the numerical example 1 are as follows. Both are within the range of each conditional expression.
Conditional expression numerical value Rn / Y ′ = 1.134
| R2 / R3 | = 2.170
dn / ds = 0.161
ds / d3 = 0.532

FIG. 3 is an optical arrangement diagram showing Example 3 of the zoom lens according to the present invention, and Table 5 shows Numerical Example 3 thereof.

In Table 5, the fifth surface, the eleventh surface, the eighteenth surface, and the nineteenth surface marked with “*” are aspheric surfaces, and the parameters according to the above-described Expression 1 in each aspheric surface are as follows.

Table 6 shows the focal length f (mm) at the wide-angle end (Wide), the intermediate focal position (Mean), the telephoto end (Tele), and the distance between the surfaces whose numerical values change according to the zooming operation. Showing change. In Table 6, A is the change in the distance between the first lens group G1 and the second lens group G2, B is the change in the distance between the second lens group G2 and the diaphragm, C is the change in the distance between the diaphragm and the third lens group G3, and D is the first. The change in the distance between the third lens group G3 and the fourth lens group G4 is shown.

Numerical values corresponding to the conditional expressions in Numerical Example 3 are as follows. Both are within the range of each conditional expression.
Conditional expression numerical value Rn / Y ′ = 1.516
| R2 / R3 | = 1.826
dn / ds = 0.177
ds / d3 = 0.668

FIG. 4 is an optical arrangement diagram showing Example 4 of the zoom lens according to the present invention, and Numerical Example 4 is shown in Table 7.

In Table 7, the fifth surface, the eleventh surface, the eighteenth surface, and the nineteenth surface marked with “*” are aspherical surfaces, and the parameters according to the above-described Expression 1 in each aspherical surface are as follows.

Table 8 shows the focal length f (mm) at the wide-angle end (Wide), the intermediate focal position (Mean), the telephoto end (Tele), and the distance between the surfaces whose numerical values change according to the zooming operation. Showing change. In Table 8, A is the change in the distance between the first lens group G1 and the second lens group G2, B is the change in the distance between the second lens group G2 and the stop, C is the change in the distance between the stop and the third lens group G3, and D is the first change. The change in the distance between the third lens group G3 and the fourth lens group G4 is shown.

Numerical values corresponding to the conditional expressions in Numerical Example 4 are as follows. Both are within the range of each conditional expression.
Conditional expression numerical value Rn / Y ′ = 1.467
| R2 / R3 | = 5.006
dn / ds = 0.272
ds / d3 = 0.586

FIG. 5 is an optical arrangement diagram showing Example 5 of the zoom lens according to the present invention, and Numerical Example 5 is shown in Table 9.

In Table 9, the fifth surface, the eleventh surface, the eighteenth surface, and the nineteenth surface marked with “*” are aspheric surfaces, and the parameters according to the above-described Expression 1 in each aspheric surface are as follows.

Table 10 shows the focal length f (mm) at the wide-angle end (Wide), the intermediate focal position (Mean), the telephoto end (Tele) at the wide-angle end (Tele) and the distance between the surfaces whose numerical values change according to the zooming operation. Showing change. In Table 10, A is the change in the distance between the first lens group G1 and the second lens group G2, B is the change in the distance between the second lens group G2 and the diaphragm, C is the change in the distance between the diaphragm and the third lens group G3, and D is the first. The change in the distance between the third lens group G3 and the fourth lens group G4 is shown.

Numerical values corresponding to the conditional expressions in Numerical Example 5 are as follows. Both are within the range of each conditional expression.
Conditional expression numerical value Rn / Y ′ = 1.568
| R2 / R3 | = 9.311
dn / ds = 0.134
ds / d3 = 0.76

FIG. 6 shows an aberration curve diagram at the short focal end of the zoom lens according to Numerical Example 1, FIG. 7 shows an aberration curve diagram at the intermediate focal length, and FIG. 8 shows an aberration curve diagram at the long focal end.
FIG. 9 shows an aberration curve diagram at the short focal point of the zoom lens according to Numerical Example 2, FIG. 10 shows an aberration curve diagram at the intermediate focal length, and FIG. 11 shows an aberration curve diagram at the long focal point.
FIG. 12 shows an aberration curve diagram at the short focal end of the zoom lens according to Numerical Example 3, FIG. 13 shows an aberration curve diagram at the intermediate focal length, and FIG. 14 shows an aberration curve diagram at the long focal end.
FIG. 15 shows an aberration curve diagram at the short focal point of the zoom lens according to Numerical Example 4, FIG. 16 shows an aberration curve diagram at the intermediate focal length, and FIG. 17 shows an aberration curve diagram at the long focal point.
FIG. 18 shows an aberration curve diagram at the short focal end of the zoom lens according to Numerical Example 5, FIG. 19 shows an aberration curve diagram at the intermediate focal length, and FIG. 20 shows an aberration curve diagram at the long focal end.
In these aberration curve diagrams, the broken line of spherical aberration represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional.

  In any embodiment, the aberration is sufficiently corrected. The distortion is 2% or less. By configuring the zoom lens as in each of the above embodiments, the half field angle is a wide field angle of 38 ° or more, the F number at the short focal point is 2.5 or less, and it is bright and small, but very good. It is clear from each aberration curve that image performance can be secured. In addition, it is also shown that, when zooming from the short focal end to the long focal end, the fourth lens group G4 is fixed with respect to the image plane and is sufficiently corrected for aberrations even with a single lens configuration. .

  Next, an embodiment of a camera device incorporating the zoom lens according to the present invention will be described with reference to FIG. FIG. 21A is a perspective view drawn so that the front side and the upper part of the camera device can be seen, and FIG. 21B is a perspective view drawn so that the upper part on the back side can be seen. A photographing lens 1 is incorporated on the front side of the housing 5 of the camera device. The photographing lens 1 may be considered as the zoom lens described above. The taking lens 1 is a zoom lens. A front end portion of the optical finder 2 and a flash (for example, a strobe light emitter) 3 are also arranged on the front side of the housing 5. A shutter button 4 is disposed on the upper surface of the housing 5. On the rear side of the housing 5, a rear end portion of the optical finder 2, a power switch 6, a liquid crystal monitor 7, operation buttons 8 for performing various operations, a memory card slot 9, and a zoom operation button 10 are arranged. Has been.

  The photographic lens 1 forms a subject image on the image plane. This camera device is a digital camera, and a light-receiving surface of an image sensor made up of, for example, a CCD is positioned on the image formation surface, and the formed subject image is converted into an electrical signal and output as an image signal. A subject image can be displayed on the liquid crystal monitor 7 by this image signal. By operating the zoom operation button 10, the first lens group G1 to the fourth lens group G4 and the diaphragm are moved in the optical axis direction as described above, and continuously change in the range from the short focal end to the long focal end. Can be doubled. By pressing the shutter button 4, the subject image formed on the image sensor at that time can be photographed, and the photographed image can be recorded. For example, a memory card loaded in the memory card slot 9 can be used as the recording medium.

  FIG. 22 shows an example of the system structure of the camera device. As shown in FIG. 22, the camera device has a photographic lens 1 and a light receiving element 13, and is configured to read an image of a photographing object formed by the photographic lens 1 by the light receiving element 13. The light receiving element 13 corresponds to the imaging element. The output from the light receiving element 13 is processed by a signal processing device 14 under the control of the central processing unit 11 and converted into digital information. In other words, the camera device has a “function of using a captured image as digital information”. The image information converted into the digital information is appropriately processed by the image processing device 12 controlled by the central processing unit 11 and then displayed on the liquid crystal monitor 7. Further, the shutter button 10 can be recorded in the semiconductor memory 15 and further transferred to a printer, a computer, or other external device via the communication card 16 or the like. The semiconductor memory 15 may be a memory card loaded in the memory card slot 9 of the camera device shown in FIG. 21, or may be a memory built in the camera device.

  There is a portable information terminal device such as a cellular phone as a device that can shoot a subject image and record a photographed image, and the zoom lens may be incorporated as a zoom lens in the portable information terminal device.

1 is an optical arrangement diagram showing Embodiment 1 of a zoom lens according to the present invention. FIG. FIG. 6 is an optical arrangement diagram showing Embodiment 2 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Example 3 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Embodiment 4 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Embodiment 5 of the zoom lens according to the present invention. It is an aberration curve figure in the short focal end of Numerical Example 1 of the zoom lens according to the present invention. It is an aberration curve figure in the intermediate focal length of Numerical Example 1 of the zoom lens according to the present invention. It is an aberration curve figure in the long focal end of Numerical Example 1 of the zoom lens according to the present invention. It is an aberration curve figure in the short focal end of Numerical Example 2 of the zoom lens according to the present invention. It is an aberration curve figure in the intermediate focal length of Numerical Example 2 of the zoom lens according to the present invention. It is an aberration curve figure in the long focal end of Numerical Example 2 of the zoom lens according to the present invention. It is an aberration curve figure in the short focal end of Numerical Example 3 of the zoom lens according to the present invention. It is an aberration curve figure in the intermediate focal length of Numerical Example 3 of the zoom lens according to the present invention. It is an aberration curve figure in the long focal end of Numerical Example 3 of the zoom lens according to the present invention. It is an aberration curve figure in the short focal end of Numerical Example 4 of the zoom lens according to the present invention. It is an aberration curve figure in the intermediate focal length of Numerical Example 4 of the zoom lens according to the present invention. It is an aberration curve figure in the long focal end of Numerical Example 4 of the zoom lens according to the present invention. It is an aberration curve figure in the short focal end of Numerical Example 5 of the zoom lens according to the present invention. FIG. 10 is an aberration curve diagram at an intermediate focal length of Numerical Example 5 of the zoom lens according to the present invention. It is an aberration curve figure in the long focal end of Numerical Example 5 of the zoom lens according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view which shows the Example of the camera apparatus or portable information terminal device concerning this invention, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. It is a block diagram which shows the system structural example of a camera apparatus.

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 1st lens 8 Lens L9 9th Lens L10 10th Lens L11 11th Lens 1 Shooting Lens 2 Viewfinder 3 Flash 4 Shutter Button 5 Housing 6 Power Switch 7 LCD Monitor 8 Operation Button 9 Memory Card Slot 10 Zoom Operation Button

Claims (12)

In order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a fourth lens having a positive focal length. And has a stop on the object side of the third lens group, and when changing the magnification from the short focal end to the long focal end, the distance between the first lens group and the second lens group increases, In a zoom lens in which the distance between the second lens group and the third lens group is decreased and the distance between the third lens group and the fourth lens group is increased,
The third lens group includes, in order from the object side , a cemented lens including a positive lens, a negative lens, and a positive lens, a positive lens on the object side from the cemented lens, and a negative lens on the image side from the cemented lens. Zoom lens to be used. When the radius of curvature of the negative lens of the negative lens constituting the cemented lens in the third lens group having a strong negative power is Rn and the maximum image height is Y ′,
0.8 <Rn / Y ′ <2.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The zoom lens according to claim 1 or 2, wherein the negative lens constituting the cemented lens in the third lens group is a biconcave lens. When the radius of curvature of the object side surface of the negative lens constituting the cemented lens in the third lens group is R2, and the radius of curvature of the image side surface is R3,
1.0 <| R2 / R3 | <10.0
The zoom lens according to claim 3, wherein the following conditional expression is satisfied. When the thickness of the negative lens constituting the cemented lens in the third lens group is dn and the thickness of the third lens group cemented lens is ds,
0.1 <dn / ds <0.4
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The zoom lens according to claim 1, wherein the cemented lens in the third lens group includes only a spherical lens. The zoom lens according to claim 1, further comprising an aspheric lens having a positive focal length on the most object side of the third lens group. The zoom lens according to claim 1, further comprising an aspheric lens having a negative focal length on the most image side of the third lens group. When the thickness of the third lens group is d3, and the thickness of the cemented lens in the third lens group is ds,
0.3 <ds / d3 <0.9
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. A camera apparatus for capturing a subject image and recording a captured image, wherein the camera apparatus includes the zoom lens according to claim 1 as a zoom lens. The camera device according to claim 10, having a function of using a captured image as digital information. A portable information terminal device capable of photographing a subject image and recording a photographed image, comprising the zoom lens according to any one of claims 1 to 9 as a zoom lens.

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