JP2010060919A - Zoom lens, zoom lens unit, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens, zoom lens unit, and electronic apparatus that achieve a further reduction in size, and that achieve a reduction in the size of an optical path bending element even in the configuration where the optical path bending element is disposed closest to an object than all the lenses of the zoom lens. <P>SOLUTION: The zoom lens includes, in order from an object side, a first lens group G1 having negative refractive power, an aperture stop STO, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The position of the first lens group G1 is fixed, and the second lens group G2 is formed of a plurality of positive lenses. To zoom from a wide-angle end to the tele-photo end, the second lens group G2 moves from the image side to the object side. The third lens group G3 is moved to correct change in an image face. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a zoom lens, a zoom lens unit, and an electronic device, and in particular, even in a case where an element that bends an optical path is arranged in the zoom lens, an electronic device such as a digital camera or a portable terminal equipped with the zoom lens. The present invention relates to a zoom lens, a zoom lens unit, and an electronic device that can be reduced in thickness.

  In recent years, personal digital assistants (PDAs) and mobile phones have become widespread, and many of them are equipped with imaging devices such as digital cameras. These image pickup devices are miniaturized by using a small CCD (Charged Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor. As these devices become widespread, image pickup devices are required to have higher resolution and higher performance along with further miniaturization, and a zoom lens is mounted on a thin casing such as a mobile phone.

  Among the zoom lenses mounted on such portable terminals such as mobile phones, the type that the most object-side lens called the conventional retractable type is driven is the limitation of the thickness of the casing of the mobile phone, dustproof, and shock resistance Although not preferred from the standpoint of performance and the like, a type using a bending optical system that bends the optical system at approximately 90 ° is advantageous in that the size in the thickness direction of a casing of a mobile phone or the like is reduced.

  As such a zoom lens, for example, a configuration in which the optical path bending element is downsized by disposing a negative lens that is stronger on the object side than the optical path bending element that bends the optical system is generally used (for example, Patent Documents). 1).

  In addition, in order to omit the space of the lens disposed on the object side of the optical path bending element, any one of the incident surface, the exit surface, and the reflecting surface of the optical path bending element is curved, so that the optical path bending element itself has a refractive power. Is also disclosed (see Patent Document 2).

In order to reduce the size of the zoom lens, a zoom lens composed of four lens groups (first lens group to fourth lens group) of negative, positive, negative, and positive from the object side is also disclosed (Patent Document). 3). In this zoom lens, the positive second lens group is composed of a positive lens and a negative lens. By disposing a negative lens on the image plane side of the second lens group, The position of the front principal point is realized on the object side from the second lens group.
JP-A-9-138347 (published May 27, 1997) JP 2003-107356 A (published April 9, 2003) JP 2005-55496 A (published March 3, 2005)

  When the lens is arranged on the object side of the optical path bending element as in the above-mentioned Patent Document 1, the optical axis of the lens on the object side of the optical path folding element and the optical path bending are caused by an assembly error (tilt) of the optical path folding element. The optical axis of the lens closer to the image plane than the element is greatly deviated, and the image quality is degraded.

  Similarly, as in Patent Document 2, when the optical path bending element itself has refractive power, the image quality deteriorates due to an assembly error of the optical path bending element. Therefore, the conventional folding zoom optical system requires a very high accuracy with respect to the attachment of the optical path bending element, and is difficult to manufacture.

  On the other hand, if the optical path bending element is arranged on the object side of all the lenses, the image quality does not deteriorate even if an assembly error of the optical path bending element occurs. However, in such a configuration, since there is no element that refracts the light beam before entering the optical path bending element, the optical path bending element becomes large, which causes a problem that it is difficult to reduce the size of the zoom lens.

  Further, in the configuration in which the optical path bending element is arranged on the object side with respect to all the lenses, in order to reduce the optical path bending element, the first lens group has a negative refractive power and further increases the refractive power. Although effective, when the optical path bending element is arranged on the object side of the zoom lens described in Patent Document 3, the second lens group is composed of a positive lens and a negative lens. Since the positive refractive power of the two lens groups is not strong, the negative refractive power of the first lens group cannot be increased. If the negative refractive power of the first lens unit is simply increased, it is necessary to increase the outer diameter of the other lenses, so that the zoom lens cannot be sufficiently reduced in size.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a zoom lens, a zoom lens unit, and an electronic apparatus that can be further reduced in size, and the zoom lens. It is an object of the present invention to provide a zoom lens, a zoom lens unit, and an electronic apparatus that can reduce the size of the optical path bending element even when the optical path bending element is arranged on the object side of all the lenses.

  In order to solve the above problem, a zoom lens according to the present invention includes, in order from the object side, a first lens group having a negative refractive power, an aperture stop, a second lens group having a positive refractive power, and a negative lens group. And a fourth lens group having a positive refractive power, the position of the first lens group is fixed, and the second lens group is composed of a plurality of positive lenses. Thus, at the time of zooming from the wide-angle end to the telephoto end, the second lens group moves from the image plane side to the object side, and the third lens group moves to correct image plane variation. It is characterized by being.

  According to the above configuration, the zoom lens can be further downsized, and the optical path bending element can be reduced even when the optical path bending element is disposed on the most object side of the zoom lens. Therefore, it is not necessary to give the optical path bending element a refractive power, and it is not necessary to attach the optical path bending element to the optical path bending element.

  Specifically, since the second lens group is a lens group composed of a plurality of lenses having a positive refractive power, the second lens group has a positive refractive power compared to the case where it is composed of a single positive lens. Can be strong. As a result, since the negative refractive power of the first lens group can be increased, the optical path bending element can be reduced in size when the optical path bending element is disposed closest to the object side of the zoom lens.

  In addition, since the positive refractive power of the second lens group can be increased, the amount of movement of the second lens group during zooming can be reduced. Further, it is possible to converge the divergent light beam after the aperture stop, suppress the spread of the light beam emitted from the second lens group, and reduce the outer diameter of the second lens group and the third lens group, This can contribute to miniaturization of the zoom lens itself. Furthermore, since the negative refractive power of the third lens group can be increased, it is possible to effectively correct field curvature.

  Further, since the aperture stop is located between the first lens group and the second lens group, the position of the aperture stop is located near the optical path bending element. The pupil position) can be close to the object side, and when the optical path bending element is disposed closest to the object side of the zoom lens, the optical path bending element can be reduced in size.

  Further, since the third lens group has a negative refractive power, the zoom lens moves in the same direction as the movement direction of the second lens group at the time of zooming, so that the length of the entire zoom lens can be suppressed. In addition, since the third lens group has a negative refractive power, there is an effect of shortening the back focus. Furthermore, the third lens group can broaden the light that is strongly converged by the second lens group, and can correct field curvature.

  In addition, since the fourth lens group has a positive refractive power, an image can be formed. The fourth lens group can correct distortion.

  In addition, since the position of the first lens group is fixed, when the optical path bending element is disposed closest to the object side of the zoom lens according to the present invention, the first lens group having negative refractive power is replaced with the optical path bending element. Therefore, the optical path bending element can be made smaller. When, for example, a prism is used as the optical path bending element, the first lens group can be disposed in contact with the prism, and the first lens group can be easily assembled.

  Further, at the time of zooming from the wide-angle end to the telephoto end, the second lens group moves from the image plane side to the object side, and the third lens group moves to correct image plane variation. With this configuration, the focal length can be changed by the movement of the second lens group, and the fluctuation of the image plane can be corrected by the movement of the third lens group.

  Accordingly, the zoom lens according to the present invention having the above-described configuration can further reduce the size of the zoom lens, and when the optical path bending element is disposed on the most object side of the zoom lens according to the present invention. Since the optical path bending element can be made small, it is not necessary to provide the optical path bending element with refractive power, and therefore it is not necessary to attach the optical path bending element with high accuracy. Therefore, the zoom lens according to the present invention is easy to manufacture. It becomes.

  In the zoom lens according to the present invention, it is preferable that the aperture stop is fixed on the object side of the second lens group.

  According to the above configuration, the aperture stop is fixed to the second lens group and moves together with the second lens group at the time of zooming, so that a decrease in Fno can be suppressed, and the second lens group and the third lens group. Can be reduced.

  In the zoom lens according to the present invention, it is preferable that the first lens group is composed of a single lens whose both surfaces are concave. The first lens group may be composed of a plurality of lenses. In that case, it is preferable that both surfaces of the lens closest to the object among the plurality of lenses have a concave shape.

  According to the above configuration, since both surfaces of the lens closest to the object side in the first lens group are concave, when the optical path bending element is disposed closest to the object side of the zoom lens according to the present invention, the first lens group. Can be arranged closer to the optical path bending element, and the optical path bending element can be made smaller. Further, since both surfaces are concave, the negative refractive power of the first lens group can be made stronger, which can further contribute to downsizing of the optical path bending element.

  In the zoom lens according to the present invention, it is preferable that the first lens group includes, in order from the object side, a lens having a concave surface on both surfaces and a lens having a convex surface on the object side.

  As described above, since the first lens group includes, in order from the object side, a lens whose both surfaces are concave and a lens whose object side is convex, it is possible to correct astigmatism and coma. it can.

  In the zoom lens according to the present invention, it is preferable that the most image side lens in the second lens group has a convex shape on the image side.

  According to said structure, since the image surface side of the lens of the most image surface side in a 2nd lens group is convex shape, the breadth of the light beam inject | emitted from a 2nd lens group can be suppressed more strongly, and a 2nd lens group. In addition, the outer diameter of the third lens group can be further reduced.

  In the zoom lens according to the present invention, it is preferable that the second lens group has a cemented lens.

  According to said structure, since a 2nd lens group has a bonded lens, chromatic aberration can be suppressed.

  In the zoom lens according to the present invention, it is preferable that the most object side lens in the second lens group has an aspherical shape.

  According to the above configuration, since the lens closest to the object side in the second lens group is located in the vicinity of the aperture stop, the lens has an aspheric shape, so that the spherical aberration can be corrected particularly effectively. Can do.

  In the zoom lens according to the present invention, it is preferable that the position of the fourth lens group is fixed with respect to the image plane.

  According to the above configuration, the zoom lens can be hermetically sealed by fixing the fourth lens group with respect to the image plane, and the zoom lens housing has a stronger structure. Can do. Therefore, with the above configuration, a compact and high-performance zoom lens having dust resistance and robustness can be realized with a simple configuration.

  The zoom lens according to the present invention preferably has an optical path bending element having no refractive power on the object side of the first lens group.

  According to the above configuration, since the optical path bending element having no refractive power is positioned on the object side of all the lenses in the zoom lens, the image quality is deteriorated even when the optical path bending element is inclined or decentered due to an assembly error. Therefore, it is easy to assemble the zoom lens.

  In the zoom lens according to the present invention, it is preferable that the optical path bending element is composed of a prism, and among the surfaces constituting the prism, all surfaces through which effective rays pass are flat.

  According to the above configuration, since the optical path bending element is a prism, the reflecting surface can be made smaller and the zoom lens can be made smaller than when a reflecting mirror or the like is used as the optical path bending element. . In addition, since all the surfaces through which effective rays pass are flat among the surfaces constituting the prism, the prism has no refractive power, so even if the prism is tilted or decentered due to assembly errors. Since the image quality does not deteriorate, the zoom lens can be easily assembled.

  A zoom lens unit according to the present invention includes the zoom lens according to the present invention and an electronic image sensor for receiving an image formed by the zoom lens.

  According to said structure, since it has the zoom lens which concerns on this invention, a small zoom lens unit can be comprised.

  In the zoom lens unit according to the present invention, it is more preferable that the zoom lens has a shutter between the second lens group and the third lens group.

  According to said structure, by having a shutter between the 2nd lens group and the 3rd lens group, the aperture diameter of a shutter can be made small and the shutter itself can be made small. In the zoom lens according to the present invention, since the light emitted from the second lens group does not spread because the second lens group is a positive lens, a shutter is disposed between the second lens group and the third lens group. For example, the aperture diameter of the shutter can be set to the same size as the aperture stop.

  An electronic apparatus according to the present invention includes the zoom lens unit according to the present invention.

  According to said structure, since the zoom lens unit which concerns on this invention is provided, an electronic device can be made thinner.

  As described above, the zoom lens according to the present invention, in order from the object side, the first lens group having a negative refractive power, the aperture stop, the second lens group having a positive refractive power, and the negative refractive power. And a fourth lens group having positive refractive power, the position of the first lens group is fixed, and the second lens group is composed of a plurality of positive lenses, and has a wide angle. At the time of zooming from the end to the telephoto end, the second lens group is moved from the image plane side to the object side, and the third lens group is moved to correct image plane fluctuation. It is characterized by that. Accordingly, the zoom lens can be further reduced in size, and when the optical path bending element is disposed closest to the object side of the zoom lens, the optical path bending element can be reduced and the manufacturing is facilitated.

[First Embodiment]
An embodiment of a zoom lens according to the present invention will be described below with reference to FIG.

  FIG. 1 is a diagram illustrating a configuration of a zoom lens according to the present embodiment. FIG. 1A shows the lens position at the wide-angle end, and FIG. 1B shows the lens position at the telephoto end. The left side of FIG. 1 shows the object side, and the right side shows the image plane side. The arrows in the figure indicate the movement of the lens during zooming, the broken arrows indicate that the position is fixed, and the solid arrows indicate that the lens moves during zooming.

  In addition, the “object side” is, in other words, the subject side and the light incident side in the zoom lens.

  As shown in FIG. 1, the zoom lens 20c of the present embodiment includes a prism (optical path bending element) P1 that bends the optical path to approximately 90 °, a first lens group G1 having negative refractive power, an aperture stop STO, and positive refraction. The second lens group G2 having power, the third lens group G3 having negative refractive power, and the fourth lens group G4 having positive refractive power.

  In the present specification, the “lens group” indicates a lump of lenses that move together during zooming, and may be composed of one lens or a plurality of lenses. This can be easily understood by those skilled in the art. When one lens group is composed of a plurality of lenses, the positional relationship of each lens in the lens group is fixed even during zooming.

  Note that IMG in FIG. 1 indicates an image plane, and an electronic image sensor for receiving an image is disposed. In addition, a cover glass CG is disposed on the object side of the image plane IMG in order to protect the electronic image sensor and the like.

  As indicated by the arrows in FIG. 1, at the time of zooming from the wide-angle end (a) to the telephoto end (b), the prism P1, the first lens group G1, the fourth lens group G4, the cover glass CG, and the image plane IMG are The second lens group G2 is monotonously moved toward the object side, and the third lens group G3 is moved toward the object side in order to correct image plane variation. In order to realize such zooming, for example, a driving member (for example, a stepping motor or the like) is disposed in each of the second lens group G2 and the third lens group G3, and can be moved individually. Further, by using a cam corresponding to the movement locus of the second lens group G2 and the third lens group G3, it is possible to move the two lens groups with one driving member.

  The prism P1 is a prism having no refractive power, and is disposed closest to the object side from all the lenses.

  Since the prism P1 has no refracting power and is arranged closest to the object side with respect to all the lenses, the lens groups G1 to G4 involved in image formation can be separated from the prism P1, so that the prism P1 has an assembly error. The image quality does not deteriorate even when tilted or eccentric. Therefore, in the zoom lens according to the present embodiment, it is not necessary to attach the prism P1 with high accuracy, and therefore it can be easily manufactured as compared with the conventional configuration.

  The first lens group G1 includes a single biconcave lens L1 having a negative refractive power. By making both surfaces concave, the negative refractive power of the first lens group G1 can be increased. Further, since the object side has a concave shape, the first lens group G1 can be as close as possible to the prism P1. In this embodiment, the first lens group G1 is fixed with respect to the prism P1. Since the first lens group G1 is fixed with respect to the prism P1, it is not necessary to provide a mechanical clearance between the prism P1 and the first lens group G1, and therefore the prism P1 and the first lens group G1. Can be made as close as possible, and therefore the prism P1 can be made smaller.

  The aperture stop STO is fixed on the object side of the second lens group G2, and moves together with the second lens group G2 at the time of zooming.

  By disposing the aperture stop STO between the first lens group G1 and the second lens group G2, the entrance pupil position (the position of the aperture stop viewed through the lens from the object side) can be made close to the prism P1. As a result, the prism P1 can be reduced. Further, since the aperture stop STO is fixed to the object side of the second lens group G2, it moves together with the second lens group G2 at the time of zooming, so that the decrease in Fno at the time of zooming is suppressed, the second lens group. It is possible to reduce the outer diameters of G2 and the third lens group G3 and to suppress fluctuations in spherical aberration.

  The second lens group G2 includes two lenses L2 and L3 having positive refractive power, and the surface closest to the image plane of the second lens group G2 is a convex surface.

  By configuring the second lens group G2 with two lenses having positive refractive power, aberration can be suppressed, and the positive refractive power of the entire second lens group G2 can be increased. Furthermore, the negative refractive power of the first lens group G1 can be increased, the fluctuation of Fno during zooming can be reduced, and the amount of movement of the second lens group G2 during zooming can be reduced. The prism P1 can be made smaller by increasing the negative refractive power of the first lens group G1. Further, since the second lens group G2 has a positive refractive power and the most image side surface is a convex surface, the light emitted from the second lens group G2 does not spread. The outer diameter of the three lens groups can be reduced. Furthermore, since the light beam emitted from the second lens group G2 does not spread, the negative refractive power of the third lens group can be increased, and the field curvature can be corrected effectively.

  In addition, it is preferable to arrange a shutter (not shown) having a small aperture diameter between the second lens group G2 and the third lens group G3. Since the second lens group G2 has a positive refractive power and the most image-side surface is a convex surface, the light emitted from the second lens group G2 does not spread, so the second lens group G2 and the third lens Since the light flux between the second lens group G2 and the third lens group G3 is reduced to the same extent as the aperture stop STO, the aperture diameter of the shutter can be reduced. Can do. The shutter may be disposed on the image plane side of the second lens group, or may be disposed on the object side of the third lens group.

  In order to reduce the aperture diameter of the shutter, it is preferable to arrange the shutter at a position where the light flux is smallest in the zoom lens. In the present invention, since the aperture stop is disposed on the object side of the second lens group, the position where the light flux becomes the smallest in the zoom lens is likely to be on the object side of the second lens group. However, since the distance between the first lens group and the second lens group is very narrow at the telephoto end, it is difficult to provide a sufficient space for installing the shutter. On the other hand, in the present invention, the second lens group is a positive lens, and the spread of the light beam emitted from the second lens group is suppressed. Therefore, with the configuration of the present invention, the shutter can be made sufficiently small even when the shutter is disposed between the second lens group and the third lens group.

  In the zoom lens according to the present invention, it is preferable that the lens disposed closest to the object side of the second lens group G2 has an aspherical shape. Since the lens disposed closest to the object side of the second lens group G2 is disposed in the vicinity of the aperture stop STO, the spherical aberration can be corrected more effectively if the lens is aspherical.

  The third lens group G3 includes a cemented lens of lenses L4 and L5, and has negative refractive power. The third lens group G3 moves to correct image plane fluctuations during zooming.

  Since the third lens group G3 has a negative refractive power, it moves to the object side in the same way as the second lens group G2 at the time of zooming, so that space can be used efficiently and the length of the entire zoom lens is suppressed. be able to. Further, since the third lens group G3 has negative refractive power, the back focus can be shortened. Further, the third lens group G3 can spread the light that is strongly converged by the second lens group G2, and can correct curvature of field.

  The fourth lens group G4 includes a single lens L6, and has positive refractive power.

  When the fourth lens group G4 has a positive refractive power, an image can be formed. In the configuration of the zoom lens according to the present invention, the fourth lens group G4 can correct distortion.

  The position of the fourth lens group G4 is preferably fixed with respect to the image plane IMG. By fixing the position of the fourth lens group G4, the zoom lens can be hermetically sealed when mounted on an electronic device such as a mobile phone, so that dustproofness is improved and the housing is made to have a strong structure. Can do.

  Numerical data are shown in Tables 1 to 3 for one example of the zoom lens according to the present embodiment. Table 1 shows numerical data in the present embodiment of the surfaces 1 to 18 shown in FIG. The rate and the Abbe number with respect to the d-line are shown.

  In the present embodiment, the surfaces 4, 5, 7, 8, 9, 10, 14, and 15 are aspherical surfaces. The “aspheric surface” indicates an aspheric shape represented by the following aspheric expression (i).

Where “K” is a conic constant, “A”, “B”, “C” and “D” are aspherical coefficients, “Y” is a distance from the optical axis, “R” is a radius of curvature at the aspherical vertex, “Z” indicates the distance in the vertical direction from the tangent plane of the aspheric vertex at the point on the aspheric surface where the distance from the optical axis is Y.

Table 2 shows numerical data on the aspheric surface in the present example. In the items represented in the floating-point format in Table 2, “E” represents the exponent base 10 and the symbol “x” is omitted. For example, “−0.12345 × 10 ⁻¹⁵ ” is expressed as “−0.12345E-15”.

  Next, Table 3 shows numerical data at the time of zooming in this example. In Table 3, “surface interval 5” means the distance (mm) between the surface 5 and the surface 6 shown in FIG. 1, and “surface interval 10” means the distance between the surface 10 and the surface 11 (mm). ) “Surface spacing 13” indicates the distance (mm) between the surface 13 and the surface 14.

Further, the zoom lens in the present embodiment satisfies the following expression. “F1” to “f4” are the focal lengths of the first lens group G1 to the fourth lens group G4, and “Lw” is the surface 6 of the aperture stop STO and the exit surface 3 of the prism P1 at the wide angle end. The distance “Lt” indicates the distance between the surface 6 of the aperture stop STO and the exit surface 3 of the prism P1 at the telephoto end.
f1 = −9.41
f2 = 5.18
f3 = −4.83
f4 = 7.75
Lw = 9.26
Lt = 2.39
Therefore, the zoom lens in the present embodiment satisfies the following expression. “Fw” indicates the focal length of the zoom lens at the wide-angle end.
| F1 / fw | = 1.61
f2 / fw = 0.88
| F3 / fw | = 0.83
Lw / Lt = 3.87
Aberration diagrams in this example are shown in FIGS. 2 shows an aberration diagram at infinity at the wide angle end, FIG. 3 shows an aberration diagram at infinity at the intermediate focal length, and FIG. 4 shows an aberration diagram at infinity at the telephoto end. Each figure shows spherical aberration, astigmatism and distortion from the left.

  In the diagram showing spherical aberration, the dotted line indicates the e-line (wavelength 546.1 nm), the solid line indicates the C-line (wavelength 656.3 nm), and the two-dot chain line indicates the g-line (wavelength 435.0 nm). In the diagram showing astigmatism, the solid line S indicates the sagittal image plane, and the dotted line M indicates the tangential image plane.

  As shown in FIGS. 2 to 4, the zoom lens according to the present embodiment exhibits good optical characteristics in terms of spherical aberration, astigmatism, and distortion at each of the wide-angle end, the intermediate focal length, and the telephoto end. .

Note that the zoom lens according to the present invention preferably satisfies the following conditional expression (1) with respect to the first lens group G1.
1.0 ≦ | f1 / fw | ≦ 4.0 (1)
By satisfying conditional expression (1), even if the optical path bending element P1 is small, Fno can be improved and brightened. If the lower limit of conditional expression (1) is not reached, it will not be bright at the telephoto end. If the upper limit of conditional expression (1) is exceeded, the size of the optical path bending element P1 becomes large in order to improve Fno.

The zoom lens according to the present invention more preferably satisfies the following conditional expression (1-1) instead of the conditional expression (1).
1.3 ≦ | f1 / fw | ≦ 2.0 (1-1)
By satisfying conditional expression (1-1), the optical path bending element P1 can be reduced in size and Fno can be improved.

The zoom lens according to the present invention preferably satisfies the following conditional expression (2) with respect to the second lens group G2.
0.5 ≦ f2 / fw ≦ 1.5 (2)
By satisfying conditional expression (2), the aberration generated in the second lens group G2 can be reduced, and the light beam emitted from the second lens group G2 can be reduced. Therefore, the second lens group G2 In addition, the outer diameter of the third lens group G3 can be further reduced. If the lower limit of conditional expression (2) is not reached, the aberration generated in the second lens group becomes large, and sufficient aberration characteristics cannot be obtained in the entire zoom lens. If the upper limit of conditional expression (2) is exceeded, the luminous flux emitted from the second lens group becomes large, and the outer diameters of the second lens group and the third lens group become large.

The zoom lens according to the present invention more preferably satisfies the following conditional expression (2-1) instead of the conditional expression (2).
0.8 ≦ f2 / fw ≦ 1.0 (2-1)
The zoom lens according to the present invention preferably satisfies the following conditional expression (3) with respect to the third lens group.
0.5 ≦ | f3 / fw | ≦ 1.5 (3)
By satisfying conditional expression (3), the Petzval sum of the entire zoom lens is reduced, and field curvature and distortion can be corrected more effectively. If the lower limit of conditional expression (3) is not reached, correction of curvature of field and distortion will be excessive, and sufficient aberration characteristics will not be obtained. If the upper limit of conditional expression (3) is exceeded, curvature of field and distortion cannot be corrected, and sufficient aberration characteristics cannot be obtained.

It is more preferable that the zoom lens according to the present invention satisfies the following conditional expression (3-1) instead of the conditional expression (3).
0.7 ≦ | f3 / fw | ≦ 0.9 (3-1)
The zoom lens according to the present invention preferably satisfies the following conditional expression (4) at the time of zooming with respect to the position of the aperture stop STO.
2.0 ≦ Lw / Lt ≦ 6.0 (4)
However, “Lw” is the distance between the aperture stop STO and the exit surface of the optical path bending element P1 at the wide angle end, and “Lt” is the distance between the aperture stop STO and the exit surface of the optical path bending element P1 at the telephoto end. Distance. By satisfying conditional expression (4), the optical path bending element P1 can be made small, and since Fno can be made favorable at the telephoto end, it can be brightened. If the lower limit of conditional expression (4) is not reached, Fno will not be good at the telephoto end, and it will not be bright enough. Moreover, if the upper limit of conditional expression (4) is exceeded, the optical path bending element P1 will become large.

The zoom lens according to the present invention more preferably satisfies the following conditional expression (4-1) instead of the conditional expression (4).
3.0 ≦ Lw / Lt ≦ 4.0 (4-1)
By satisfying conditional expression (4-1), the optical path bending element P1 can be reduced in size, and the balance of Fno can be improved.

  As described above, the zoom lens according to the present invention can be further reduced in size, and even when the optical path bending element is disposed on the most object side of the zoom lens, the optical path bending element can be reduced. Since it is not necessary to give refractive power to the optical path bending element, it is not necessary to attach the optical path bending element with high accuracy, and the manufacturing is facilitated.

[Second Embodiment]
Another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, the same number is attached | subjected to the component which has the same function as the component concerning 1st Embodiment, and the description is abbreviate | omitted. In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 5 is a diagram showing a configuration of a zoom lens according to another embodiment of the present invention. FIG. 5A shows the lens position at the wide-angle end, and FIG. 5B shows the lens position at the telephoto end. The left side of FIG. 5 shows the object side, and the right side shows the image plane side. The arrows in the figure indicate the movement of the lens during zooming, the dotted arrows indicate that the position is fixed, and the solid arrows indicate that the lens moves during zooming.

  As shown in FIG. 5, in the present embodiment, the second lens group G2 is composed of a lens L2 having a positive refractive power and a bonded lens composed of lenses L3 and L4 having a positive refractive power as a whole. The The third lens group G3 is composed of a single lens L5.

  In the present embodiment, since the second lens group G2 that moves at the time of zooming is composed of a plurality of lenses having positive refractive power, chromatic aberration is likely to occur, so that a lens on the image plane side of the second lens group G2 is attached. By using the matching lens, it is possible to correct chromatic aberration occurring in the second lens group G2.

  Numerical data are shown in Tables 4 to 6 for one example of the zoom lens according to the present embodiment. Table 4 shows numerical data in this embodiment of the surfaces 1 to 18 shown in FIG. Further, the aspheric surfaces in Tables 4 and 5 have the aspheric shape represented by the above formula (i).

  In the present embodiment, the surfaces 4, 5, 7, 8, 14, and 15 are aspherical surfaces. Table 5 shows numerical data on the aspheric surface in the present embodiment.

  Next, Table 6 shows numerical data at the time of zooming in this example. In Table 6, “surface interval 5” means the distance (mm) between the surface 5 and the surface 6 shown in FIG. 5, and “surface interval 11” means the distance (mm) between the surface 11 and the surface 12. ) “Surface spacing 13” indicates the distance (mm) between the surface 13 and the surface 14.

Further, the zoom lens in the present embodiment satisfies the following expression. “F1” to “f4” are the focal lengths of the first lens group G1 to the fourth lens group G4, and “Lw” is the surface 6 of the aperture stop STO and the exit surface 3 of the prism P1 at the wide angle end. The distance “Lt” indicates the above distance at the telephoto end.
f1 = -10.05
f2 = 5.15
f3 = -4.80
f4 = 9.14
Lw = 10.89
Lt = 2.85
Therefore, the zoom lens in the present embodiment satisfies the following expression.
| F1 / fw | = 1.66
f2 / fw = 0.85
| F3 / fw | = 0.79
Lw / Lt = 3.82
Aberration diagrams in this example are shown in FIGS. FIG. 6 shows an aberration diagram at infinity at the wide angle end, FIG. 7 shows an aberration diagram at infinity at the intermediate focal length, and FIG. 8 shows an aberration diagram at infinity at the telephoto end. Each figure shows spherical aberration, astigmatism and distortion from the left.

  As shown in FIGS. 6 to 8, the zoom lens according to the present embodiment exhibits good optical characteristics in terms of spherical aberration, astigmatism, and distortion at each of the wide-angle end, the intermediate focal length, and the telephoto end. .

[Third Embodiment]
Another embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, the same number is attached | subjected to the component which has the same function as the component concerning 1st Embodiment, and the description is abbreviate | omitted. In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 9 is a diagram showing a configuration of a zoom lens according to another embodiment of the present invention. FIG. 9A shows the position of the lens at the wide-angle end, and FIG. 9B shows the position of the lens at the telephoto end. The left side of FIG. 9 shows the object side, and the right side shows the image plane side. The arrows in the figure indicate the movement of the lens during zooming, the dotted arrows indicate that the position is fixed, and the solid arrows indicate that the lens moves during zooming.

  As shown in FIG. 9, in the present embodiment, the first lens group G1 includes a biconcave lens L1 and a meniscus lens L2 having a convex surface on the object side, which is disposed on the image side. The second lens group G2 includes a lens L3 having positive refractive power and a bonded lens composed of lenses L4 and L5 having positive refractive power as a whole. The third lens group G3 is composed of one lens L6, and the fourth lens group G4 is composed of one lens L7.

  The first lens group G1 includes a lens L1 having a concave surface on both sides and a meniscus lens L2 having a convex surface on the object side, which is disposed on the image side thereof, thereby correcting astigmatism and coma. Can be done effectively.

  Further, since the lens on the image plane side of the second lens group G2 is a cemented lens, chromatic aberration generated in the second lens group G2 can be corrected.

  Numerical data are shown in Tables 7 to 9 for one example of the zoom lens according to the present embodiment. Table 7 shows numerical data in this embodiment of the surfaces 1 to 20 shown in FIG. Further, the aspheric surfaces in Tables 7 and 8 are aspherical shapes represented by the above formula (i).

  In the present embodiment, the surfaces 4, 5, 6, 9, 10, 16 and 17 are aspherical surfaces. Table 8 shows numerical data about the aspherical surface in the present example.

  Next, Table 9 shows numerical data at the time of zooming in this example. In Table 9, “surface interval 7” means the distance (mm) between the surface 7 and the surface 8 shown in FIG. 9, “surface interval 13” means the distance (mm) between the surface 13 and the surface 14, “Surface spacing 15” indicates the distance (mm) between the surface 15 and the surface 16.

Further, the zoom lens in the present embodiment satisfies the following expression. “F1” to “f4” are the focal lengths of the first lens group G1 to the fourth lens group G4, and “Lw” is the surface 8 of the aperture stop STO and the exit surface 3 of the prism P1 at the wide angle end. The distance “Lt” indicates the above distance at the telephoto end.
f1 = -10.14
f2 = 5.40
f3 = −4.49
f4 = 7.79
Lw = 10.48
Lt = 3.38
Therefore, the zoom lens in the present embodiment satisfies the following expression.
| F1 / fw | = 1.60
f2 / fw = 0.85
| F3 / fw | = 0.71
Lw / Lt = 3.10
Aberration diagrams in this example are shown in FIGS. FIG. 10 shows aberration diagrams at infinity at the wide angle end, FIG. 11 shows aberration diagrams at infinity at the intermediate focal length, and FIG. 12 shows aberration diagrams at infinity at the telephoto end. Each figure shows spherical aberration, astigmatism and distortion from the left.

  As shown in FIGS. 10 to 12, the zoom lens in the present embodiment exhibits good optical characteristics in terms of spherical aberration, astigmatism, and distortion at each of the wide-angle end, the intermediate focal length, and the telephoto end. .

[Fourth Embodiment]
Next, a zoom lens unit that can include the zoom lens according to the first to third embodiments described above, and an electronic apparatus including the zoom lens unit will be described with reference to FIGS.

  FIGS. 13A to 13C are diagrams showing the configuration of the mobile phone (electronic device) of this embodiment. 13A is the front side of the mobile phone 30, FIG. 13B is the back side of the mobile phone 30, and FIG. 13C is the side surface side of the mobile phone 30. .

  The mobile phone 30 of this embodiment has an imaging function (camera function). Therefore, as shown in FIGS. 13A to 13C, the mobile phone 30 includes a housing 31, a zoom lens unit 32, a speaker unit 33, a microphone unit 34, an input unit 35, a monitor unit 36, and a light. The unit 37 and the shutter button 38 are provided at least. In the present embodiment, the surface shown in FIG. 13A where the input unit 35 and the monitor unit 36 are provided is referred to as a front surface.

  The speaker unit 33 and the microphone unit 34 are used for inputting and outputting audio information. The monitor unit 36 is used to output video information. In the present embodiment, the monitor unit 36 is also used to display information obtained from the zoom lens unit 32. The light unit 37 is used as an illumination device for illuminating the subject when the zoom lens unit 32 captures the subject.

  By operating the shutter button 38 or the input unit 35, the subject can be imaged by the zoom lens unit 32. The captured image is signal-processed in the mobile phone 30 and displayed on the monitor unit 36. The captured image can be stored as electronic data in the mobile phone 30 or stored in an external recording device.

  The zoom lens unit 32 will be described in detail with reference to FIG.

  14A and 14B are cross-sectional views of the zoom lens unit 32. FIG. FIG. 14A shows a state in which the zoom lens unit 32 shown in FIG. 13C is cut in parallel to the side surface of the mobile phone 30 shown in FIG. 13C. ) Shows a state in which the zoom lens unit 32 shown in FIG. 13B is cut in parallel with the back surface of the mobile phone 30 shown in FIG. As shown in FIG. 14A, the zoom lens unit 32 includes a solid-state imaging unit 20a, a unit package 20b, a zoom lens 20c, and a guide shaft 24.

  The solid-state imaging unit 20a includes an electronic imaging element 21, which is an electronic component including an electrical conversion unit for converting the light beam that has passed through the zoom lens 20c into an electrical signal, a support substrate 22, and a flexible printed circuit board 23. is doing.

  The electronic imaging device 21 is formed with an electrical conversion unit in which pixels are two-dimensionally arranged at the center of the light receiving side surface, and a signal processing circuit is formed around the electrical conversion unit. The signal processing circuit includes a driving circuit unit that sequentially drives each pixel to obtain a signal charge, an A / D conversion unit that converts each signal charge into a digital signal, and a signal that forms an image signal output using the digital signal. It consists of a processing unit. A large number of pads (not shown) are provided in the vicinity of the outer edge of the light receiving side surface of the electronic image sensor 21 in the present embodiment, and the electronic image sensor 21 is connected to the support substrate 22. The type of the electronic imaging element 21 is not particularly limited. Specifically, a CCD sensor, a CMOS sensor, or the like can be used.

  The support substrate 22 is a hard substrate that supports the electronic imaging device 21 and the unit package 20b on one surface thereof. The other surface of the support substrate 22 (the surface opposite to the surface on which the electronic imaging element 21 is supported) is provided with a flexible printed circuit board 23 having one end connected thereto. The support substrate 22 is provided with a large number of signal transmission pads on both the front and back surfaces. One surface is connected to the electronic image pickup device 21 and the other surface is connected to the flexible printed circuit board 23.

  The flexible printed circuit board 23 is supplied with a voltage and a clock signal for driving the electronic image pickup device 21 from an external circuit (for example, a control circuit included in an apparatus equipped with the zoom lens unit 32), and also receives a digital YUV signal. It is a board | substrate which enables it to output to the exterior. Y is a luminance signal, U is a color difference signal between red and the luminance signal, and V is a color difference signal between blue and the luminance signal.

  The unit package 20b is a light-shielding body that is fixedly arranged so as to cover the electronic imaging element 21 on the surface of the support substrate 22 on the electronic imaging element 21 side. On the side of the electronic image pickup element 21, a wide opening is formed so as to surround the electronic image pickup element 21 and is in contact with the support substrate 22. The first to fourth lens groups described above can be disposed inside.

  The guide shaft 24 is provided so as to sandwich the zoom lens 20c along the moving direction of the lens in the zoom lens 20c, and both ends thereof are fixed to the unit package 20b. Furthermore, the frame supporting each of the second lens group G2 and the third lens group G3 is supported by the guide shaft 24 so as to be movable in the length direction of the guide shaft 24. When the lens moves, such as during zooming, the second lens group G2 and the third lens group G3 move along the guide shaft 24.

  In addition, other components can be appropriately arranged in the zoom lens unit 32. For example, an infrared light cut filter can be provided. For example, the infrared light cut filter can be fixedly disposed between the zoom lens 20 c and the electronic image sensor 21. Further, for example, a film having an infrared light cut function may be attached to the cover glass CG shown in FIG.

  In the present embodiment, the zoom lens unit 32 is arranged on the back side of the mobile phone 30 shown in FIG. 13, but the arrangement method and the direction of the zoom lens unit 32 are not limited thereto. is not.

  Further, as shown in FIGS. 13A to 13C, the mobile phone 30 according to this embodiment is a so-called folding in which an upper housing and a lower housing are connected via a hinge. As an example, the portable cellular phone 30 is not limited to the folding cellular phone 30 in which the zoom lens unit 32 can be mounted.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The zoom lens of the present invention can be further reduced in size as compared with the conventional configuration, and even when the optical path bending element is disposed on the most object side of the zoom lens, the optical path bending element can be reduced. Since it is not necessary to give the optical path bending element a refractive power and it is not necessary to attach the optical path bending element with high accuracy, the manufacturing becomes easy.

  Therefore, the present invention can be applied to any device equipped with an image sensor such as a digital camera or a mobile phone having an image capturing function.

It is a figure which shows the structure of the zoom lens which concerns on one Embodiment of this invention. Aberration diagrams at infinity at the wide-angle end are shown. An aberration diagram at infinity at the intermediate focal length is shown. An aberration diagram at infinity at the telephoto end is shown. It is a figure which shows the structure of the zoom lens which concerns on other embodiment of this invention. Aberration diagrams at infinity at the wide-angle end are shown. An aberration diagram at infinity at the intermediate focal length is shown. An aberration diagram at infinity at the telephoto end is shown. It is a figure which shows the structure of the zoom lens which concerns on other embodiment of this invention. Aberration diagrams at infinity at the wide-angle end are shown. An aberration diagram at infinity at the intermediate focal length is shown. An aberration diagram at infinity at the telephoto end is shown. It is the figure which showed the structure of one Embodiment of the portable telephone which concerns on this invention. It is sectional drawing which showed the structure of the zoom lens unit which is one structure of the principal part of the portable telephone shown in FIG.

Explanation of symbols

P1 prism (optical path bending element)
G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group STO Aperture stop 20a Solid-state imaging unit 20b Unit package 20c Zoom lens 21 Electronic imaging device 22 Support substrate 23 Flexible printed circuit board 24 Guide shaft 30 Portable type Telephone unit 31 Case 32 Zoom lens unit 33 Speaker unit 34 Microphone unit 35 Input unit 36 Monitor unit 37 Light unit 38 Shutter button

Claims (14)

From the object side,
A first lens group having negative refractive power;
An aperture stop,
A second lens group having a positive refractive power;
A third lens group having negative refractive power;
A fourth lens group having positive refractive power,
The position of the first lens group is fixed,
The second lens group includes a plurality of positive lenses,
At the time of zooming from the wide-angle end to the telephoto end, the second lens group is moved from the image plane side to the object side, and the third lens group is moved to correct image plane variation. A zoom lens characterized by   The zoom lens according to claim 1, wherein the aperture stop is fixed to the object side of the second lens group.   3. The zoom lens according to claim 1, wherein the first lens group includes one lens whose both surfaces are concave.   3. The zoom lens according to claim 1, wherein the first lens group includes a plurality of lenses, and a lens closest to the object among the plurality of lenses has a concave surface on both sides.   3. The zoom lens according to claim 1, wherein the first lens group includes, in order from the object side, a lens having a concave surface on both surfaces and a lens having a convex surface on the object side.   The zoom lens according to any one of claims 1 to 5, wherein the lens closest to the image plane in the second lens group has a convex shape on the image plane side.   The zoom lens according to claim 1, wherein the second lens group includes a bonded lens.   The zoom lens according to claim 1, wherein a lens closest to the object side in the second lens group has an aspherical shape.   The zoom lens according to claim 1, wherein the position of the fourth lens group is fixed with respect to the image plane.   The zoom lens according to any one of claims 1 to 9, further comprising an optical path bending element having no refractive power on the object side of the first lens group. The optical path bending element is composed of a prism,
The zoom lens according to claim 10, wherein all surfaces through which effective light rays pass among the surfaces constituting the prism are flat. The zoom lens according to any one of claims 1 to 11,
A zoom lens unit comprising: an electronic image pickup device for receiving an image formed by the zoom lens.   The zoom lens unit according to claim 12, wherein the zoom lens has a shutter between the second lens group and the third lens group.   An electronic apparatus comprising the zoom lens unit according to claim 12.