JP4948124B2 - Zoom lens, camera device, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens used in a digital camera, a video camera, and the like, and the digital camera, video camera, other camera device, and portable information terminal device provided with the zoom lens as a photographing lens.

  Currently, various cameras, in particular digital cameras, have a strong need for higher image quality, smaller size, wider angle, larger aperture, and the like. In the future, it will be necessary to develop technologies to meet these demands. Therefore, it is required to be a zoom lens as a photographing lens, and to have high image quality, a small size, a wide angle, and a large aperture corresponding to a high-definition light receiving element exceeding 5 million pixels.

  As a conventional zoom lens, 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 positive lens A fourth lens unit having a focal length, a stop on the object side of the third lens unit, and the first lens unit and the second lens unit at the time of zooming from the short focal end to the long focal end; The distance is increased, the distance between the second lens group and the third lens group is decreased, the distance between the third lens group and the fourth lens group is changed, and the third lens group is sequentially changed from the object side to the positive lens, the negative lens, There is a lens composed of a positive lens and a negative lens (for example, see the embodiment of FIG. 13 of Patent Document 1 and Patent Document 2).

  In the embodiment of the zoom lens described in FIG. 13 of Patent Document 1, the third lens group includes a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens in order from the object side. The third lens and the fourth lens are cemented. In the zoom lens described in Patent Document 2, the third lens group includes, in order from the object side, a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens. The second lens is cemented, and the third lens and the fourth lens are cemented.

  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. 4 lens groups, a stop on the object side of the third lens group, and when 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 lens group and the third lens group is decreased, the distance between the third lens group and the fourth lens group is changed, and the negative lens, the positive lens, and the negative lens among the plurality of lenses constituting the third lens group are changed. A zoom lens in which three lenses are joined is also known (see, for example, Patent Document 3).

JP 2005-62228 A, JP 2003-241091 A JP 2004-286811 A

  As in the example described in FIG. 13 of Patent Document 1, the third lens group includes a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens in order from the object side. In the zoom lens in which the third lens and the fourth lens are cemented, suppressing deterioration in image quality due to the eccentricity of the negative second lens with respect to the positive third lens or the negative fourth lens is 3 It is difficult to compare with a cemented lens.

  In the zoom lens described in Patent Document 2, the third lens group is configured by a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens in order from the object side. The lens and the second lens are cemented, and the positive third lens and the negative fourth lens are cemented. As described above, in a zoom lens using two sets of cemented lenses, the optical axes of the two groups of cemented lenses may be shifted due to decentering or the like in a state where each lens is assembled. The chromatic aberration of magnification, which becomes a problem when the angle of view is changed, is generated asymmetrically, and unnatural color blur tends to occur. On the other hand, if a cemented lens of three lenses is used, it is possible to reduce the occurrence of eccentricity during assembly on the two cemented surfaces. Even in the zoom lens described in Patent Document 2, a wide angle of view of a half angle of view of 42 ° or more cannot be achieved, and the F number at the short focal end cannot be made 3.0 or less.

  The zoom lens described in Patent Document 3 includes, in order from the object side, a first lens group having a positive focal length, a second lens group having a negative focal length, and a third lens group having a positive focal length. A fourth lens group having a positive focal length, a stop closer to the object side than the third lens group, and the first lens group and the second lens upon zooming from the short focal end to the long focal end The distance between the groups increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group changes, and the third lens group is a positive first lens, a negative lens The second lens, the positive third lens, the negative fourth lens, and the positive fifth lens, and the second, third, and fourth lenses are cemented.

  In the zoom lens disclosed in Patent Document 3, the third lens group is the third lens group as compared with a type in which the lens closest to the image side of the third lens group is a positive lens and the lens closest to the image side of the third lens group is a negative lens. The principal point of becomes the image plane side. For this reason, it is difficult to shorten the optical distance between the second lens group and the third lens group, and it is difficult to increase the zooming efficiency, that is, the amount of change in focal length with respect to the amount of lens movement. The third lens group is composed of five lenses. Therefore, it is desired to reduce the size of the third lens group by reducing the number of lenses and thereby reduce the cost.

  The present invention has been made in view of the above-described problems of the prior art, has high performance with little aberration, can achieve a wide angle of view of a half angle of view of 42 ° or more, and has an F number at the short focal end. An object of the present invention is to provide a zoom lens that is sufficiently small and can suppress deterioration in image quality due to manufacturing and assembly errors.

It is another object of the present invention to provide a zoom lens that is small in size and capable of reducing performance deterioration due to manufacturing errors while further reducing aberrations.
It is another object of the present invention to provide a zoom lens capable of reducing performance deterioration due to manufacturing errors while further reducing aberrations.
It is another object of the present invention to provide a zoom lens that can further reduce aberrations.
It is another object of the present invention to provide a zoom lens capable of reducing performance deterioration due to manufacturing errors while further reducing aberrations.

In addition, the present invention achieves a wide angle of view with less aberration, a half angle of view of 42 ° or more, and a zoom lens that is sufficiently small while having an F number at the short focal length of 3.0 or less, as a photographing optical system. The purpose is to provide a small, high-quality camera device.
It is another object of the present invention to provide a camera device having a function of using photographed image information as digital information.

In addition, the present invention achieves a wide angle of view with less aberration, a half angle of view of 42 ° or more, and a zoom lens that is sufficiently small while having an F number at the short focal length of 3.0 or less, as a photographing optical system. The purpose is to provide a small, high-quality portable information terminal device used.

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. The third lens group has a fourth lens group having a positive focal length, and has a stop on the object side of the third lens group. When changing the magnification from the short focus end to the long focus end, In the zoom lens in which the distance between the 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 changed, the third lens The group includes a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens in order from the object side, and the negative second lens, the positive third lens, and the negative fourth lens. three lenses are bonded, the second record of the third lens group to dn from the object side surface of the first lens of the third lens group The distance to the image side surface of the figure, when the fw and the focal length at the short focal end,
0.9 <dn / fw <1.5
Satisfying the conditional expression is the most important feature.

In the invention of claim 2, when R311 is the radius of curvature of the object side surface of the first lens of the third lens group and fw is the focal length of the short focal end,
1.5 <R311 / fw <2.2
It satisfies the following conditional expression.

In the invention according to claim 3 , when R311 is a radius of curvature of the object side surface of the first lens of the third lens group, and R322 is a radius of curvature of the image side surface of the second lens of the third lens group,
0.1 <(R311−R322) / (R311 + R322) <0.3
It satisfies the following conditional expression.

In the invention according to claim 4 , when Nd2 is a refractive index at the d-line of the second lens of the third lens group, and Nd3 is a refractive index at the d-line of the third lens of the third lens group,
Nd2-Nd3> 0.25
It satisfies the following conditional expression.

In the invention according to claim 5 , when d8 is the center thickness of the third lens of the third lens group and fw is the focal length of the short focal point,
0.6 <d8 / fw <1.4
It satisfies the following conditional expression.

The invention described in claim 6 is characterized in that the positive first lens of the third lens group is an aspherical lens.
The invention according to claim 7 is characterized in that the image side surface of the fourth lens of the third lens group is an aspherical surface.
The invention according to claim 8 is characterized in that, among the three lenses joined to the third lens group, only the image side surface of the fourth lens is an aspherical surface.

According to the ninth aspect of the present invention, the first to third lens groups are movable with respect to the image plane and the fourth lens group is movable with respect to the image plane during zooming from the short focal end to the long focal end. It is fixed.

A tenth aspect of the present invention is a camera device having a photographing zoom lens, wherein the zoom lens according to any one of the first to ninth aspects is provided as the photographing zoom lens.
According to an eleventh aspect of the present invention, the camera apparatus according to the eleventh aspect has a function of converting photographed image information into digital information.

A twelfth aspect of the present invention is a portable information terminal device having a photographing zoom lens, wherein the zoom lens according to any one of the first to ninth aspects is provided as the photographing zoom lens .

According to the present invention, a sharp image with little aberration can be obtained, a wide field angle of 42 ° or more can be achieved, and the F number at the short focal end is 3.0 or less. , A zoom lens that is sufficiently small can be provided. By applying such a zoom lens to a digital camera, for example, a small digital camera capable of obtaining high image quality can be realized.

In addition, according to the present invention, it is possible to provide a zoom lens that is small and has little image deterioration due to manufacturing errors while being a high-performance lens with little aberration. By applying such a zoom lens to a camera, a small and more stable camera can be obtained.
In addition, according to the present invention, a high-performance zoom lens with less aberration can be provided, and by applying such a zoom lens to a camera, a camera capable of obtaining a higher quality image can be realized.
In addition, according to the present invention, it is possible to provide a zoom lens that is a high-performance zoom lens with less aberrations and less image degradation due to manufacturing errors. By applying such a zoom lens to a camera, the camera can be stably operated with high performance. Can be realized.

In addition, according to the present invention, a high-performance camera with little aberration, which realizes a wide angle of view of 42 ° or more and a short focal end F number of 3.0 or less, is sufficient. It is possible to provide a small camera that can obtain a high-quality image using a small zoom lens. Therefore, the user can take a high-quality image with a compact camera having excellent portability.
In addition, according to the present invention, a high-performance digital camera with little aberration, which realizes a wide field angle of 42 ° or more and a short focal end F number of 3.0 or less, is sufficient. In addition, it is possible to provide a digital camera that uses a small zoom lens and can obtain a small and high-quality image. Therefore, the user can take a high-quality image with a compact digital camera excellent in portability and handle the image as digital information.

In addition, according to the present invention, a high-performance portable information terminal device with little aberration that realizes a wide field angle of 42 ° or more and a short focus end F number of 3.0 or less. Therefore, it is possible to provide a small-sized and high-quality portable information terminal device using a zoom lens that is sufficiently small. Therefore, a high-quality image can be taken 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.
1 to 4 show first, second, third, and fourth embodiments of the zoom lens according to the present invention, respectively. In these embodiments, numerical values such as the radius of curvature, thickness, distance between lenses, and refractive index on both surfaces of the lens are different, and the form of the lens group, the form of the lens constituting each lens group, and the distance between optical elements. Since the basic configuration is the same, first, the basic configuration will be described with reference to FIG.

  In FIG. 1, the left side is the object side, and the right side is the image plane side. In FIG. 1, the zoom lens includes, in order from the object side, a first lens group G1 having a positive focal length, a second lens group G2 having a negative focal length, and a third lens group G3 having a positive focal length. And a fourth lens group G4 having a positive focal length. A stop is provided on the object side of the third lens group G3. In the lower part of FIG. 1, the movement of each lens group at the time of zooming from the short focal end to the long focal end is drawn with a line. As can be seen from these lines, the distance between the first lens group G1 and the second lens group G2 increases during zooming from the short focal end to the long focal end, and the second lens group G2 and the third lens group G3 The distance is decreased, and the distance between the third lens group G3 and the fourth lens group G4 is changed. In zooming from the short focal end to the long focal end, the first lens group G1 is configured to approach the image plane side partway and then move away from the image plane. The fourth lens group G4 is a focus lens that is fixed during zooming and moves in the optical axis direction during focusing.

  The first lens group G3 includes two lenses, a negative meniscus first lens L1 having a convex surface directed toward the object side, and a positive meniscus second lens L2 cemented to the first lens L1, in order from the object side. A first lens L1 and a second lens L2 are disposed. The second lens group G2 includes a negative meniscus first lens L3, a negative biconcave second lens L4, and a positive biconvex third lens L5. The first lens L3 is sequentially formed from the object side. The second lens L4 and the third lens L5 are arranged.

The third lens group G3 includes a positive first lens L6, a negative second lens L7, a positive third lens L8, and a negative fourth lens L9 in order from the object side. Further, the third lens group G3 has the following characteristics. The negative second lens L7, the positive third lens L8, and the negative fourth lens L9 are cemented, and this configuration is one of the features. The positive first lens L6 is spaced forward from the above-mentioned three lenses that are joined.
The fourth lens group G4 is composed of one positive lens L10.

  As described above, the zoom lens according to the present invention employs a four-group zoom type in which a lens group having a positive focal length is preceded, and each lens group is moved as indicated by a line at the bottom of FIG. As a result, efficient zooming is achieved. In the case of such a zoom lens type, focusing can be performed by extending all the lens groups, but it is desirable to perform focusing with the fourth lens group G4.

  In order to realize a zoom lens that has few aberrations from the short focus end to the long focus end and has a high resolving power, aberration fluctuations due to zooming must be kept small. In particular, the third lens group G3, which is responsible for the zooming action, needs to be favorably corrected for aberrations over the entire zooming range. Therefore, the configuration of the third lens group is important. Therefore, as described above, the third lens group G3 is composed of four lenses in order from the object side: the positive lens L6, the negative lens L7, the positive lens L8, and the negative lens L9. As described above, the configuration including two positive lenses and two negative lenses makes it easier to correct axial chromatic aberration and lateral chromatic aberration compared to the configuration of three positive lenses and one negative lens. It has become. When the negative lens of the third lens group is composed of one lens, the degree of freedom of selection of the glass that is the material of the lens is less than when the negative lens of the third lens group is composed of two lenses. It becomes difficult to correct aberrations of the entire zoom lens.

Further, by using the lens L9 closest to the image side of the third lens group G3 as a negative lens, the principal point of the third lens group G3 becomes the object side. Therefore, the optical distance between the second lens group G2 and the third lens group G3 can be shortened, and the zooming efficiency can be improved.
Further, the third lens group G3 is constituted by the positive lens L6, the negative lens L7, the positive lens L8, and the negative lens L9, so that the positive lens L6 exchanges aberrations with the negative lens L7 and the negative lens L9, that is, one lens. The positive lens L8 tends to exchange aberration with the negative lens L9 by mutually complementing the aberrations such as correcting the generated aberration with the other lens.

  A large amount of aberration is exchanged between the object side surface of the first lens L6 and the image side surface of the second lens L7 in the third lens group G3, and the difference in the height of the light beam at each surface becomes important. If the distance between the object side surface of the first lens L6 and the image side surface of the second lens L7 is increased, the difference in light height between the two surfaces increases, and the manufacturing error sensitivity, that is, the adverse effect of the manufacturing error on the lens performance increases. Can be suppressed.

  Therefore, in the embodiment of the present invention, the negative second lens L7, the positive third lens L8, and the negative fourth lens L9 of the third lens group G3 are cemented, and the object side surface of the positive lens L6 and the negative lens are joined. By sufficiently securing the air space on the image side surface of L7, the adverse effect of the manufacturing error in the third lens group G3 on the lens performance is reduced.

The positive lens L6 and the negative lens L7 of the third lens group G3 may be cemented, and the positive lens L8 and the negative lens L9 may be cemented. However, in order to reduce the adverse effect of manufacturing errors on the lens performance, the positive lens The thickness of the cemented lens by L6 and the negative lens L7 increases, resulting in an increase in cost.
The third lens group G3 is composed of four lenses, but can be handled as two components, that is, one positive lens L6 and three cemented lenses, so that it can be expected to improve work efficiency during manufacturing.

  As described above, the F number is as bright as 3.0 or less, a wide field angle of 42 ° or more can be achieved, and adverse effects on imaging performance due to manufacturing errors can be suppressed. A zoom lens can be obtained.

In order to obtain a zoom lens that has small aberration and high performance, and that is small in size and capable of reducing manufacturing error sensitivity, it is desirable that the above-described lens system configuration satisfies the following conditional expression (1). .
0.9 <dn / fw <1.5 (1)
dn is the distance from the object side surface of the positive first lens L6 of the third lens group G3 to the image side surface of the negative second lens L7, and fw is the focal length of the entire zoom lens at the short focal end. Conditional expression (1) The dn is defined within a predetermined range.

  Since the aberration is exchanged between the object side surface of the positive first lens L6 and the image side surface of the negative second lens L7, the height of the light beam passing through these two surfaces is required in order to perform good aberration correction. is important. If the lower limit value of conditional expression (1) is exceeded, the height of the off-axis principal ray on the image side surface of the negative second lens L7 becomes too small, making it difficult to correct astigmatism and coma. When the upper limit of conditional expression (1) is exceeded, the axial marginal ray height on the image side surface of the negative second lens L7 becomes too small, and it becomes difficult to correct spherical aberration. Further, it is disadvantageous for downsizing the third lens group G3.

In order to obtain a zoom lens that has small aberration and high performance, and that is small in size and capable of reducing manufacturing error sensitivity, it is desirable that the following conditional expression is satisfied in the configuration of the lens system described above.
1.5 <R311 / fw <2.2 (2)
R311 is the radius of curvature of the object side surface of the positive first lens L6 of the third lens group G3, and fw is the focal length of the entire zoom lens at the short focal end. Conditional expression (2) defines the curvature radius R311 of the object side surface of the first lens L6 within a predetermined range.
When the lower limit value of conditional expression (2) is exceeded, the refractive power on the object side surface becomes too large and the manufacturing error sensitivity becomes high. If the upper limit value of conditional expression (2) is exceeded, the axial marginal ray passing through the third lens group becomes high, and it becomes difficult to correct spherical aberration and the like. In addition, the third lens group becomes larger.

In order to obtain a high-performance zoom lens with small aberration, it is desirable that the following conditional expression is satisfied in the configuration of the lens system described above.
0.1 <(R311−R322) / (R311 + R322) <0.3 (3)
R311 is the radius of curvature of the object side surface of the positive first lens L6 of the third lens group G3, and R322 is the radius of curvature of the image side surface of the negative second lens L7 of the third lens group G3.

  Since the aberration is exchanged between the object side surface of the positive first lens L6 and the image side surface of the negative second lens L7, the positive first lens L6 exceeds the lower limit of the conditional expression (3). The aberration generated on the object side surface of the negative lens L7 is larger than the aberration generated on the image side surface of the negative second lens L7. If the upper limit of conditional expression (3) is exceeded, the image side surface of the negative second lens L7 is generated. This aberration becomes larger than the aberration generated on the object side surface of the positive first lens L6, and in any case, it is difficult to balance the aberration.

In order to obtain a high-performance zoom lens with smaller aberrations, it is desirable to satisfy the following conditional expression in the configuration of the lens system described above.
Nd2-Nd3> 0.25 (4)
Nd2 is the refractive index at the d-line of the negative second lens L7 of the third lens group G3, and Nd3 is the refractive index at the d-line of the positive third lens L8 of the third lens group G3. Conditional expression (4) stipulates that the difference in refractive index between the two is greater than a certain value. More specifically, it is defined that the refractive index of the second lens L7 is different from the refractive index of the third lens L8 by a certain value or more.
When the lower limit value of conditional expression (4) is exceeded, the difference in refractive index between the second lens L7 and the third lens L8 in the third lens group G3 becomes small, so that the aberration generated on the image side surface of the second lens L7 becomes small. Therefore, it becomes difficult to exchange aberration between the image side surface of the second lens L7 and the object side surface of the third lens L8.

In order to obtain a zoom lens having a small size and higher performance, it is desirable to satisfy the following conditional expression in the configuration of the lens system described above.
0.6 <d8 / fw <1.4 (5)
d8 is the center thickness of the positive third lens L8 of the third lens group G3, and fw is the focal length of the entire zoom lens at the short focal end.
The two cemented surfaces that join the first lens L7, the second lens L8, and the third lens L9 of the third lens group G3 have different distances from the stop, respectively, and how light rays on the optical axis and off the optical axis pass. Different. Due to the presence of the two joint surfaces as described above, axial chromatic aberration and lateral chromatic aberration can be corrected to some extent independently.
Therefore, if the lower limit value of conditional expression (5) is exceeded, the distance between the two joint surfaces is small, so that it is difficult to sufficiently correct axial chromatic aberration and lateral chromatic aberration. When the upper limit value of conditional expression (5) is exceeded, it is difficult to correct coma and the like. Further, the third lens group G3 is increased in size.

  In order to obtain a higher-performance zoom lens, the positive first lens L6 of the third lens group G3 is preferably an aspheric lens. In the positive first lens L6, since the luminous flux is the thickest, an aspherical effect can be obtained to correct spherical aberration and coma aberration. More preferably, the object side surface of the positive first lens L6 is aspheric.

  In order to obtain a higher performance zoom lens, it is desirable that the image side surface of the negative lens L9 closest to the image plane of the third lens group G3 is an aspherical surface. Since the on-axis ray and the off-axis ray are separated from each other, an aspherical effect can be obtained in image plane correction.

  In order to reduce the influence due to the manufacturing error, it is desirable that only the image side surface of the negative fourth lens L9 is aspheric in the three-piece cemented lens of the third lens group G3. When an aspheric lens is used, it is necessary to suppress the influence of the aspheric axis eccentricity by adjustment or the like. However, if a plurality of lenses are cemented, it becomes impossible to adjust the aspherical axis decentering in the cemented lens, so that only the image side surface of the negative fourth lens L9 is non-exposed in the cemented lens of the third lens group G3. It should be spherical.

  Further, it is desirable that the fourth lens group G4 is fixed with respect to the image plane during zooming from the short focal end to the long focal end. By keeping the fourth lens group G4 in a fixed position during zooming, consideration is given to simplifying the lens barrel configuration and securing the accuracy of decentering between the lens groups. Of course, if aberration correction is prioritized, it is advantageous to move all the lens groups. However, doing so complicates the structure of the lens barrel and easily causes manufacturing errors.

Examples of the zoom lens according to the present invention are specifically shown below by numerical values. The meanings of symbols used in each numerical example are as follows.
f: focal length of entire 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: 6 Next aspheric coefficient A8: 8th order aspheric coefficient A10: 10th order aspheric coefficient However, the aspherical surface used here is the reciprocal (paraxial curvature) of the paraxial radius of curvature, and the high from the optical axis. When H is H, it is defined by the following equation.

  FIG. 1 shows an optical arrangement of Numerical Example 1 of the zoom lens according to the present invention. In all of Numerical Example 1 and below, and up to Numerical Example 4, as described above, the lens unit includes the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4. It is composed of lenses having the same shape and number as already described. A stop is provided on the object side of the third lens group G3, and a filter is disposed between the fourth lens group G4 and the image plane. Each lens group is supported by an appropriate support member, and during zooming, it moves as described above for each lens group.

Numerical Example 1 is shown in Table 1.

In Table 1 showing Numerical Example 1, the fifth surface, the eleventh surface, the sixteenth surface, and the seventeenth surface marked with “*” are aspheric surfaces. The parameters are as follows:

Table 2 shows the change in the distance between the lens groups during zooming in Numerical Example 1. In Table 2, A is the distance between the first lens group G1 and the second lens group G2, B is the distance between the second lens group G2 and the diaphragm, C is the distance between the diaphragm and the third lens group G3, and D is the third lens group G3. And the interval of the fourth lens group. “Wide” indicates a short focus (wide angle) end, “Mean” indicates an intermediate focal length, and “Tele” indicates a long focus (telephoto) end.

The numerical values according to the conditional expressions (1) to (5) in the numerical example 1 are as shown in Table 3, and are within the range of the conditional expressions.

  FIG. 5 is an aberration curve diagram at the short focal point of the zoom lens according to Numerical Example 1, FIG. 6 is an aberration curve diagram at the intermediate focal length of the zoom lens according to Numerical Example 1, and FIG. 7 is the length of the zoom lens according to Numerical Example 1. Aberration curve diagrams at the focal end are shown. As is clear from these aberration curve diagrams, the aberration of the zoom lens according to Numerical Example 1 is sufficiently corrected. By configuring the zoom lens as in Numerical Example 1, a wide field angle of 42 ° or more can be realized, the F number at the short focal end can be made 3.0 or less, and the size is small. , Very good image performance can be obtained. Also, it is shown that even when the fourth lens group G4 has a single lens configuration, the aberration is sufficiently corrected.

FIG. 2 shows an optical arrangement of Numerical Example 2 of the zoom lens according to the present invention. Table 4 shows the numerical values of each part of Numerical Example 2.

In Table 4 showing Numerical Example 2, the fifth surface, the eleventh surface, the sixteenth surface, and the seventeenth surface marked with “*” are aspherical surfaces, and the above “Equation 1” is applied to each aspherical surface. The parameters are as follows:

Table 5 shows the change in the distance between the lens groups during zooming in Numerical Example 2. In Table 5, A is the distance between the first lens group G1 and the second lens group G2, B is the distance between the second lens group G2 and the diaphragm, C is the distance between the diaphragm and the third lens group G3, and D is the third lens group G3. And the interval of the fourth lens group. “Wide” indicates a short focus (wide angle) end, “Mean” indicates an intermediate focal length, and “Tele” indicates a long focus (telephoto) end.

The numerical values of the conditional expressions (1) to (5) in Numerical Example 2 are as shown in Table 6 and are within the range of the conditional expressions.

  8 is an aberration curve diagram at the short focal point of the zoom lens according to Numerical Example 2, FIG. 9 is an aberration curve diagram at the intermediate focal length of the zoom lens according to Numerical Example 2, and FIG. 10 is the length of the zoom lens according to Numerical Example 2. Aberration curve diagrams at the focal end are shown. As is apparent from these aberration curve diagrams, the aberration of the zoom lens according to Numerical Example 2 is sufficiently corrected. By configuring the zoom lens as in Numerical Example 2, it is possible to achieve a wide angle of view of 42 ° or more and a F-number at the short focus end of 3.0 or less, while being compact. , Very good image performance can be obtained. Also, it is shown that even when the fourth lens group G4 has a single lens configuration, the aberration is sufficiently corrected.

FIG. 3 shows an optical arrangement of Numerical Example 3 of the zoom lens according to the present invention. Table 7 shows the numerical values of each part of Numerical Example 3.

In Table 7 showing Numerical Example 3, the fifth surface, the eleventh surface, the sixteenth surface, and the seventeenth surface marked with “*” are aspherical surfaces, and the above “Equation 1” is applied to each aspherical surface. The parameters are as follows:

Table 8 shows changes in the distance between the lens groups during zooming in Numerical Example 3. In Table 8, A is the distance between the first lens group G1 and the second lens group G2, B is the distance between the second lens group G2 and the diaphragm, C is the distance between the diaphragm and the third lens group G3, and D is the third lens group G3. And the interval of the fourth lens group. “Wide” indicates a short focus (wide angle) end, “Mean” indicates an intermediate focal length, and “Tele” indicates a long focus (telephoto) end.

Numerical values of the conditional expressions (1) to (5) in Numerical Example 3 are as shown in Table 9 and are within the range of the conditional expressions.

  FIG. 11 is an aberration curve diagram at the short focal end of the zoom lens according to Numerical Example 3, FIG. 12 is an aberration curve diagram at the intermediate focal length of the zoom lens according to Numerical Example 3, and FIG. 13 is the length of the zoom lens according to Numerical Example 3. Aberration curve diagrams at the focal end are shown. As is apparent from these aberration curve diagrams, the aberration of the zoom lens according to Numerical Example 3 is sufficiently corrected. By constructing a zoom lens as in Numerical Example 3, a wide field angle of 42 ° or more can be realized, and the F number at the short focal end can be made 3.0 or less. , Very good image performance can be obtained. Also, it is shown that even when the fourth lens group G4 has a single lens configuration, the aberration is sufficiently corrected.

FIG. 4 shows an optical arrangement of Numerical Example 4 of the zoom lens according to the present invention. Table 10 shows the numerical values of each part of Numerical Example 4.

In Table 10 showing Numerical Example 4, the fifth surface, the eleventh surface, the sixteenth surface, and the seventeenth surface marked with “*” are aspheric surfaces, and the above-mentioned “Equation 1” is applied to each aspheric surface. The parameters are as follows:

Table 11 shows changes in the distance between the lens groups during zooming in Numerical Example 4. In Table 11, A is the distance between the first lens group G1 and the second lens group G2, B is the distance between the second lens group G2 and the diaphragm, C is the distance between the diaphragm and the third lens group G3, and D is the third lens group G3. And the interval of the fourth lens group. “Wide” indicates a short focus (wide angle) end, “Mean” indicates an intermediate focal length, and “Tele” indicates a long focus (telephoto) end.

The numerical values according to the conditional expressions (1) to (5) in the numerical example 4 are as shown in Table 12 and are within the range of the conditional expressions.

  14 is an aberration curve diagram at the short focal point of the zoom lens according to Numerical Example 4, FIG. 15 is an aberration curve diagram at the intermediate focal length of the zoom lens according to Numerical Example 4, and FIG. 16 is the length of the zoom lens according to Numerical Example 4. Aberration curve diagrams at the focal end are shown. As is clear from these aberration curve diagrams, the aberration of the zoom lens according to Numerical Example 4 is sufficiently corrected. By configuring the zoom lens as in Numerical Example 4, a wide field angle of 42 ° or more can be realized, and the F number at the short focal end can be reduced to 3.0 or less. , Very good image performance can be obtained. Also, it is shown that even when the fourth lens group G4 has a single lens configuration, the aberration is sufficiently corrected.

  The zoom lens according to the present invention described above can be applied as a photographing lens for digital cameras, video cameras, and other various camera devices. Further, it can be applied as a photographing lens of a camera attached to a portable information terminal device such as a mobile phone or a PDA. FIG. 17 shows an embodiment of a “camera device” using a zoom lens according to the present invention. FIG. 17A is a perspective view of the front side as viewed obliquely from above, and FIG. 17B is a view of the back side as viewed from obliquely upward. The camera apparatus has a zoom lens according to one of the several embodiments described above as the photographic lens 1. The camera device has a housing 5. On the front side of the housing 5, the photographing lens 1, the optical finder 2, and the light emitting unit 3 of the light emitter are arranged. A shutter button 4 is disposed on the upper surface of the housing 5. On the back side of the housing 5, an eyepiece of the optical finder 2, a power switch 6, a liquid crystal monitor 7, operation buttons 8, a memory card slot 9, and a zoom operation switch 10 are arranged.

  FIG. 18 is a block diagram showing the system structure of the camera device. As shown in FIG. 18, the camera device has a photographic lens 1 and a light receiving element 13 disposed on an image plane connected by the photographic lens 1. An image of the object to be photographed formed by the photographing lens 1 is configured to be read by the light receiving element 13, and 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. Is done. In other words, the camera device has a “function of using a captured image as digital information”. The captured image information including digital information is input to the liquid crystal monitor 7 under the control of the central processing unit 11, and the captured image can be displayed on the liquid crystal monitor 7 in real time. Alternatively, captured image information can be stored in the semiconductor memory 15, and the stored image information can be recalled under the control of the central processing unit 11 and displayed on the liquid crystal monitor 7. The captured image information can be transmitted to an external terminal, a printer, a network, or the like via the communication card 16 or the like.

  According to the camera device and the portable information terminal device according to the present invention, the zoom lens capable of obtaining the above-described effects is provided, thereby realizing a wide field angle of 42 ° or more and an F number at the short focal end. Can be reduced to 3.0 or less, and a camera device and a portable information terminal device that can obtain a very good image performance while being small can be obtained.

FIG. 2 is an optical arrangement diagram showing Numerical Example 1 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Numerical Example 2 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Numerical Example 3 of the zoom lens according to the present invention. FIG. 6 is an optical arrangement diagram showing Numerical Example 4 of the zoom lens according to the present invention. FIG. 4 is an aberration curve diagram at a short focal point of the zoom lens according to Numerical Example 1. FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Numerical Example 1. 6 is an aberration curve diagram at a long focal end of the zoom lens according to Numerical Example 1. FIG. FIG. 6 is an aberration curve diagram at a short focal end of a zoom lens according to Numerical Example 2. FIG. 6 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Numerical Example 2. FIG. 6 is an aberration curve diagram at a long focal end of a zoom lens according to Numerical Example 2. FIG. 10 is an aberration curve diagram at a short focal end of a zoom lens according to Numerical Example 3. FIG. 10 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration curve diagram at the long focal end of the zoom lens according to Numerical Example 3; FIG. 9 is an aberration curve diagram at a short focal end of a zoom lens according to Numerical Example 4; FIG. 10 is an aberration curve diagram at an intermediate focal length of the zoom lens according to Numerical Example 4; In the aberration curve diagram at the long focal end of the zoom lens according to Numerical Example 4, the broken line of spherical aberration represents the sine condition, the solid line in the diagram of astigmatism represents sagittal, and the broken line represents meridional. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the digital camera which shows embodiment of the camera apparatus concerning this invention, Comprising: (A) is a perspective view of the front side, (B) is a perspective view of 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 (3rd lens group (First lens)
L7 7th lens (2nd lens of 3rd lens group)
L8 8th lens (3rd lens of 3rd lens group)
L9 9th lens (4th lens in the 3rd lens group)
L10 10th 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 switch

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. made from the group, has a diaphragm on the object side of the third lens group, upon zooming from the short focal end to a long focal end, the interval between the first lens group and the second lens group increases, in the interval between the second lens group and the third lens group decreases, the zoom lens in which the distance between the third lens group and the fourth lens group is changed,
The third lens group includes, in order from the object side, a positive first lens, a negative second lens, a positive third lens, and a negative fourth lens. The negative second lens, the positive third lens, Three negative fourth lenses are joined ,
When dn is the distance from the object side surface of the first lens of the third lens group to the image side surface of the second lens of the third lens group, and fw is the focal length of the short focal point,
0.9 <dn / fw <1.5
A zoom lens that satisfies the following conditional expression: The zoom lens according to claim 1, wherein R311 is a radius of curvature of the object side surface of the first lens of the third lens group, and fw is a focal length of the short focal point.
1.5 <R311 / fw <2.2
A zoom lens that satisfies the following conditional expression: The zoom lens according to claim 1 or 2, wherein R311 is a radius of curvature of the object side surface of the first lens of the third lens group, and R322 is a radius of curvature of the image side surface of the second lens of the third lens group,
0.1 <(R311−R322) / (R311 + R322) <0.3
A zoom lens that satisfies the following conditional expression: The zoom lens according to any one of claims 1 to 3, wherein Nd2 is a refractive index at the d-line of the second lens of the third lens group, and Nd3 is a refractive index at the d-line of the third lens of the third lens group. ,
Nd2-Nd3> 0.25
A zoom lens that satisfies the following conditional expression: The zoom lens according to any one of claims 1 to 4, wherein d8 is a center thickness of the third lens of the third lens group, and fw is a focal length of the short focal point.
0.6 <d8 / fw <1.4
A zoom lens that satisfies the following conditional expression: 6. The zoom lens according to claim 1, wherein the positive first lens of the third lens group is an aspherical lens. 7. The zoom lens according to claim 1, wherein the image side surface of the fourth lens in the third lens group is an aspherical surface . 8. The zoom lens according to claim 7, wherein, of the three lenses joined to the third lens group, only the image side surface of the fourth lens is an aspherical surface . 9. The zoom lens according to claim 1, wherein the third lens group from the first lens group is movable with respect to the image plane upon zooming from the short focal end to the long focal end, and the fourth lens. A zoom lens, wherein the group is fixed with respect to the image plane . A camera device having a zoom lens for photographing, wherein the camera device has the zoom lens according to claim 1 as the zoom lens for photographing. 11. The camera apparatus according to claim 10, wherein the camera apparatus has a function of converting photographed image information into digital information. A portable information terminal apparatus having a zoom lens for photographing, wherein the portable information terminal apparatus has the zoom lens according to claim 1 as the photographing zoom lens.

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