JP2007058168A - Zoom lens, optical module, and mobile terminal - Google Patents

Abstract

Provided are a zoom lens, an optical module, and a portable terminal that are excellent in mass productivity and can obtain a good image quality while shortening the overall length of the lens.
In order from the object side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit L3 having a positive refractive power are provided. In the zoom lens 1 that is moved and zoomed, the second lens unit L2 includes three lenses, and includes at least one positive lens and at least one negative lens. Since the three lenses in the group L2 are cemented, a zooming function is mainly performed, and the assembly of the second group with increased sensitivity is facilitated.
[Selection] Figure 1

Description

  The present invention mainly relates to a zoom lens suitable for a camera using a solid-state imaging device such as a digital still camera, a video camera, or a surveillance camera, and more particularly to a camera attached to a mobile phone or a small information terminal device. The present invention relates to a small zoom lens, an optical module, and a portable terminal that are suitable and have a simple configuration.

In recent years, portable information terminals and mobile phones have become widespread, and an increasing number of image sensors have built-in compact digital cameras and digital video units that use CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors. .
When such a digital camera or the like is made compact by using an image sensor having a relatively small effective area of the light receiving surface, it is necessary to reduce the size of the optical system.

As a small zoom lens with a small number of lenses used in a digital camera or the like having an image sensor with a small effective area, two lenses, a first lens group having a negative refractive power and a second lens group having a positive refractive power, are conventionally used. There has been proposed a so-called short zoom type two-group zoom lens that is configured by a group and performs zooming by changing the distance between both lenses (see, for example, Patent Document 1).
In these short zoom type zoom lenses, zooming is performed by moving the second lens unit having a positive refractive power, and image point positions associated with zooming are moved by moving the first lens unit having a negative refractive power. Correction is performed. In the lens configuration composed of these two lens groups, the zoom magnification is about twice.

  Furthermore, in order to bring the entire lens into a compact shape while having a high zoom ratio of 2 times or more, a third lens unit having a negative or positive refractive power is arranged on the image side of the two-unit zoom lens for high magnification. A so-called three-group zoom lens has been proposed in which various aberrations that occur with the correction are corrected.

  Further, in recent years, as a three-group zoom lens with a small number of lenses, the first lens group is composed of a single lens and the second lens group is composed of a positive lens, a negative lens, and a positive lens as disclosed in Patent Document 2, for example. There has been proposed a zoom lens having a small number of lenses constituting each lens group constituted by three lenses and the third lens group constituted by one negative lens.

  Further, as a three-group zoom lens with a small number of lens elements, the lens system is very compact to be mounted on a mobile phone as in Patent Document 3, for example, and the first lens group, the second lens group, and the third lens group are all compact. A zoom lens composed of a single lens has been proposed.

Further, as a three-group zoom lens with a small number of lenses, the first lens group is composed of two lenses, a negative lens and a positive lens, as in Patent Document 4, for example, and the second lens group is composed of a positive lens and a positive lens. There have been proposed zoom lenses with a small number of lenses that constitute each lens group, which is composed of four lenses, a negative lens and a positive lens, and the third lens group is composed of one positive lens.
JP 2001-330773 A Japanese Patent Laying-Open No. 2005-77692 Japanese Patent Laid-Open No. 2005-77793 JP 2002-323654 A

  The two-group zoom lens disclosed in Patent Document 1 has disadvantages such as a relatively large number of lenses in each lens group, a long overall lens length, and a high manufacturing cost. In order to keep it, the zoom ratio was about twice.

  On the other hand, although the three-group zoom lens disclosed in Patent Documents 2 and 4 has a small number of lens elements, the lens sensitivity of the second lens group that mainly performs zooming increases, and is incorporated into a lens frame during mass production. The tight tolerances are disadvantageous for the supply of stable optical performance.

  In addition, the zoom lens disclosed in Patent Document 3 having one lens group is suitable for downsizing because each lens group has one lens structure, but in order to correct various aberrations. It is disadvantageous, and has a drawback that satisfactory performance cannot be obtained with respect to the improvement in optical performance accompanying the increase in the number of pixels in recent years.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens, an optical module, and a portable terminal that are excellent in mass productivity while achieving a reduction in the overall length of the lens, can be reduced in size, and can obtain a desired good image quality.

  In order to achieve the above object, an aspect of the present invention is a zoom lens having an imaging optical system having a zooming function for an imaging device, wherein the imaging optical system is arranged in order from the object side. A first lens group having a negative refractive power; a second lens group having a positive refractive power; and a third lens group having a positive refractive power. The second lens group includes three lenses. The lens has at least one positive lens and at least one negative lens, and three lenses in the second lens group are formed by bonding.

  Preferably, at least one surface of the lens in the second lens group is an aspherical surface.

  Preferably, the second lens group is formed of a cemented lens of a positive lens, a first negative lens, and a second negative lens in order from the object side.

Preferably, when the focal length of the second lens group is f2 and the focal length of the entire system at the wide angle end is fw, the following conditional expression (1) is satisfied.
1.3 <f2 / fw <2.1 (1)

Preferably, the lens arranged closest to the image side of the second lens group is a meniscus negative lens having an aspheric surface on the image side and a convex surface facing the object side, and a radius of curvature of the object side surface. If Ra is Ra and the focal length of the entire system at the wide angle end is fw, the following conditional expression (2) is satisfied.
1.25 <Ra / fw <15 (2)

  Preferably, the lens disposed closest to the image side of the second lens group is a meniscus negative lens having an aspheric surface on the image side and a convex surface facing the object side, and the aspheric surface has a shape of light. An aspherical surface whose negative refractive power is stronger than the spherical shape from the axial center to the periphery.

Preferably, when the focal length of the first lens unit is f1, the focal length of the third lens unit is f3, and the focal length of the entire system at the wide angle end is fw, the following conditional expressions (3) and (4) ) Is satisfied.
−3.0 <f1 / fw <−1.9 (3)
f3 / fw> 2.4 (4)

  Preferably, during zooming from the wide-angle end to the telephoto end, the first lens group moves along a convex locus on the image side, the second lens group moves monotonously on the object side, and the third lens group Moves to the image side.

  Preferably, the first lens group includes two lenses, a negative lens and a positive lens.

  Preferably, the first lens group includes, in order from the object side to the image side, two lenses, a negative lens having a concave shape on both sides and a meniscus positive lens having a convex surface on the object side.

  An optical module according to a second aspect of the present invention includes a zoom lens having an imaging optical system having a zooming function for an imaging device, and a lens holder that holds the zoom lens, and the imaging The optical system includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side, The second lens group includes three lenses, and includes at least one positive lens and at least one negative lens. Three lenses in the second lens group are cemented. Is formed.

  A mobile terminal according to a third aspect of the present invention includes an optical module and a housing that houses the optical module, and the optical module includes an imaging optical unit that has a scaling function for an imaging device. A first lens group having a negative refractive power, and a positive refraction, the zoom lens having a zoom lens and a lens holder that holds the zoom lens, wherein the imaging optical system is disposed in order from the object side. A second lens group having a positive power and a third lens group having a positive refractive power. The second lens group includes three lenses, and includes at least one positive lens, It has one or more negative lenses, and the lenses in the second lens group are formed by joining three lenses.

  Preferably, power supply means is provided, and the optical module is supplied with power by the power supply means.

  According to the present invention, it is possible to provide a zoom lens that is excellent in mass productivity while achieving a reduction in the overall length of the lens, can be downsized, and can obtain a desired good image quality.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram illustrating a basic configuration of the zoom lens according to the present embodiment.

  The zoom lens 1 in FIG. 1 is configured as a zoom lens having a zoom ratio (magnification ratio) of 2.8 times and an F number of 3.3 (wide-angle end) to 6.0 (telephoto end).

As shown in FIG. 1, the zoom lens 1 of the present embodiment includes a first lens unit L1 having a negative refractive power (optical power = reciprocal of focal length), a second lens unit L2 having a positive refractive power, and a positive lens unit. A third lens unit L3 having refractive power, an aperture stop SP disposed on the object side of the second lens unit L2, a glass block G, and an image plane IP are configured.
In the present embodiment, the imaging optical system includes a first lens group L1, a second lens group L2, a third lens group L3, and an aperture stop SP.
As the image plane IP, a photosensitive surface of a solid-state imaging device such as a CCD sensor or a CMOS sensor is arranged.
The glass block G is a glass block that is provided in a design corresponding to a crystal low-pass filter, an infrared cut filter, or the like.
In the present embodiment, in the drawing, the left side is the object side (front) OBJS, and the right side is the image side (rear).

  Hereinafter, the configuration and operation of the zoom lens of the present embodiment will be described.

In the zoom lens of this embodiment, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves substantially reciprocally along a locus convex to the image side, the second lens unit L2 moves to the object side, and the third lens The group L3 moves to the image side.
The main zooming is performed by the movement of the second lens unit L2, and the image point is moved along with the zooming by the reciprocating movement of the first lens unit L1 and the movement of the third lens unit L3 in the image side direction. It is corrected.

The third lens unit L3 shares the increase in the refractive power of the entire zoom lens system as the image sensor is downsized.
Due to the action of the third lens unit L3, the refractive power of a so-called short zoom system constituted by the first lens unit L1 and the second lens unit L2 can be reduced, and in particular, the first lens unit L1 is configured. It suppresses the occurrence of aberrations in the lens and achieves good optical performance.
Further, the telecentricity on the image side necessary for an imaging apparatus using a solid-state imaging device or the like is achieved by making the third lens unit L3 serve as a field lens.

The aperture stop SP is disposed on the most object side (between the first lens group L1 and the second lens group L2) of the second lens group L2.
Thereby, the distance between the entrance pupil on the wide angle side and the first lens unit L1 is shortened, and an increase in the outer diameter of the lenses constituting the first lens unit L1 is suppressed.
Furthermore, since it is possible to set the first lens unit L1 and the third lens unit L3 so as to cancel off-axis aberrations with the aperture stop SP interposed therebetween, it is good without increasing the number of constituent lenses of each lens unit. Has obtained excellent optical performance.

  Next, the configuration of each lens group will be described in more detail.

The first lens unit L1 includes two lenses, a negative lens and a positive lens.
The second lens unit L2, in order from the object side to the image side, has a biconvex positive lens, a biconcave negative lens, a concave surface on the image side, and the absolute value of the refractive power of the concave surface is an object. It is composed of a cemented lens in which three negative lenses that are larger than the side surface are bonded together.

  The configuration of each lens group will be described in more detail. The first lens group L1 includes, in order from the object side to the image side, a negative lens 11 having a concave shape on both sides and a meniscus positive lens 12 having a convex surface on the object side. It consists of two lenses.

The second lens unit L2 includes, in order from the object side to the image side, a biconvex positive lens 21 whose absolute value of refractive power is larger on the object side than the image side, and a negative lens 22 having concave surfaces on both sides. The negative lens 23 has a concave shape on the image side surface, and the absolute value of the refractive power of the concave surface is larger than that on the object side surface.
These three lenses 21 to 3 are a group of cemented lenses whose surfaces are bonded together with an adhesive. In this embodiment, a UV adhesive is used as an adhesive for bonding the surfaces.

  In the present embodiment, the negative lens 22 of the second lens unit L2 is a biconcave lens in which the absolute value of the refractive power is larger on the object side than on the image side. In this way, the Rs on both sides may be the same.

  The third lens unit L3 includes a positive lens 31, and is a biconvex lens in which the absolute value of refractive power is larger on the object side than on the image side.

The first lens unit L1 has a role of forming an off-axis chief ray in the center of the aperture stop SP and forms an off-axis aberration, particularly on the wide-angle side, since the refraction amount of the off-axis chief ray is large. Astigmatism and distortion are likely to occur.
Therefore, in the present embodiment, the first lens unit L1 is composed of the negative lens 11 and the positive lens 12 that can suppress the increase in the lens diameter closest to the object side, as in the case of a normal wide-angle lens.

  Further, an aspheric surface in which the negative refractive power is weakened around the image side lens surface of the negative lens 11 having a biconcave shape, and the negative refractive power is weakened around the concave surface of the meniscus-shaped positive lens 12. By forming an aspherical surface, astigmatism and distortion are corrected in a well-balanced manner, and the first lens unit L1 is configured with a small number of lenses of two, which contributes to compactness.

  In addition, each lens constituting the first lens unit L1 uses a resin material, and each lens is molded by injection molding, so that it can be mass-produced at low cost, and high manufacturability even if an aspherical surface is used. Can be secured.

Further, the members constituting the first lens unit L1 are made of a resin material including a lens frame. Generally, when a resin material having a large temperature dependency of the refractive index is used, the focal position shift increases when the environment changes. .
As a result, it is necessary to increase the amount of movement of the focus group. However, when one resin negative lens 11 and one resin positive lens 12 are arranged in an appropriate shape as in this configuration, each lens The generated focal position deviation cancels out, and the focal position deviation is small even when the environment changes, and it is possible to ensure good performance.

  In the second lens unit L2, the biconvex positive lens 21 having a large refractive power on the object side is arranged on the object side, thereby reducing the refraction angle of the off-axis chief ray emitted from the first lens unit L1, and the axis The occurrence of various external aberrations is suppressed.

Further, the positive lens 21 of the second lens unit L2 is a lens having the highest height of the on-axis light beam, and is a lens mainly involved in correction of spherical aberration and coma aberration. If an aspherical surface capable of correcting aberration performance satisfactorily is formed here, aberration correction is good at the time of design, but on the other hand, tolerance sensitivity required at the time of manufacturing becomes strong, and mass productivity tends to deteriorate.
Therefore, in the present embodiment, the convex shape on the object side of the positive lens 21 is also designed so that the refractive power does not become extremely large.

  The negative lens 22 disposed on the image side of the positive lens 21 of the second lens unit L2 has a concave shape on both sides, and the object side surface cancels aberrations generated on the image side surface of the positive lens 21. The image side surface cancels out aberrations occurring on the object side surface of the negative lens 23.

The negative lens 23 disposed on the most image side of the second lens unit L2 has a concave surface on the image side, and the refractive power of the concave surface is larger than that on the object side. Aberrations occurring on the object side surface are canceled.
Further, by making the image side surface of the negative lens 23 an aspherical surface in which negative refractive power is increased in the periphery, particularly coma aberration and field curvature are corrected more satisfactorily.

Further, the positive lens 21, the negative lens 22, and the negative lens 23 constituting the second lens group L2 are bonded to each other on the adjacent surfaces as described above.
At the time of bonding, since the bonding can be performed while managing the amount of eccentricity using a transmission eccentricity measuring device, the eccentricity tolerance can be kept small, and good performance can be maintained.
In addition, when performing adhesion | attachment, the measuring device which measures the amount of eccentricity may be a reflection eccentricity measuring device.

  Also, by sticking the lens surfaces together, each lens is put in a lens frame, and the variation in surface distance due to the tolerance of the lens frame only depends on the lens thickness, so the performance variation during mass production is reduced and good It is possible to maintain a good performance.

  The third lens unit L3 includes the biconvex positive lens 31 as described above, and has a role as a field lens for image side telecentricity.

  In the present embodiment, the positive lens 31 is a biconvex positive lens. However, for example, a meniscus lens having a convex image side may be used.

Here, during zooming from the wide-angle end to the telephoto end, when the third lens unit L3 moves to the image side, the back focus decreases, and the imaging magnification of the third lens unit L3 increases on the telephoto side.
That is, when the third lens unit L3 is moved to the image side during zooming, the third lens unit L3 eventually shares the zooming action. As a result, the amount of movement of the second lens unit L2, which is the main variable power group, can be reduced, so that a space for movement of the second lens unit L2 can be saved, contributing to downsizing of the entire system.

On the other hand, in the zoom lens 1 according to the present embodiment, when the subject distance is changed from an infinitely distant object to a close object, the third lens unit L3 is moved to the object side and focusing is performed to achieve good performance. Is maintained.
For this reason, even if the imaging magnification of the third lens unit L3 is too strong, the focal length variation of the entire system due to focusing becomes large, which is not preferable. Therefore, the focal length of the third lens unit L3 is set appropriately.

When focusing is performed by the third lens unit L3, it is possible to prevent an increase in the load on the actuator because it has a relatively small diameter and is composed of one lens.
Furthermore, the first lens unit L1 and the second lens unit L2 can be simply linked by a cam or the like and moved during zooming, so that the mechanical structure can be simplified and the accuracy can be improved.

Further, when performing focusing with the third lens unit L3, during zooming from the wide-angle end to the telephoto end, as described above, the third lens unit L3 is moved to the image side, so that at the telephoto end where the amount of focusing movement is large. The third lens unit L3 is located closer to the image side.
Accordingly, it is possible to minimize the total amount of movement of the third lens unit L3 required for zooming and focusing, and as a result contributes to downsizing of the entire system.

In the case of shooting by changing the subject distance from an infinitely distant object to a close object, focusing may be performed by moving the first lens unit L1 or extending the entire system on the object side.

  As described above, in this embodiment, each lens unit L1, L2, and L3 has a lens configuration that achieves both desired refractive power arrangement and aberration correction, so that the entire system is compact while maintaining good performance. Has been realized.

  Furthermore, in the zoom lens 1 of the present embodiment, the following conditions are satisfied in order to obtain good optical performance and to reduce the size of the entire lens system.

(1-1) The following conditions are preferable for shortening the overall lens length of the optical system.
1.3 <f2 / fw <2.1 (Condition 1)
Here, f2 represents the focal length of the second lens unit L2, and fw represents the focal length at the wide-angle end of the entire system.

  Exceeding the upper limit of conditional expression (1) is not preferable because the amount of movement of the second lens unit L2 during zooming increases and the overall length of the optical system becomes longer. On the other hand, when the lower limit value of conditional expression (1) is exceeded, the total length of the optical system becomes short, but the focal length of the second lens unit L2 becomes too short, and aberration correction over the entire zoom range becomes difficult, which is not preferable.

More preferably, the numerical range of conditional expression (1) is set so as to satisfy the following conditional expression (1a).
1.5 <f2 / fw <1.9 (1a)

(1-2) The following are preferable conditions for facilitating production and obtaining good optical performance.
1.25 <Ra / fw <15 (Condition 2)
Here, Ra represents the radius of curvature of the object side surface of the negative lens 23, and fw represents the focal length at the wide angle end of the entire system.

  Exceeding the upper limit value of conditional expression (2) is preferable because the curvature of the object side surface of the negative lens 23 of the second lens unit L2 becomes too loose, the stability of the material is poor at the time of manufacture, and the amount of eccentricity increases. Absent. On the other hand, if the lower limit value of conditional expression (2) is exceeded, the curvature of the object side surface becomes too tight and it is difficult to secure the edge of the negative lens 23, which is not preferable.

(1-3) The following conditions are preferable for good aberration correction of the optical system.
−3.0 <f1 / fw <−1.9 (Condition 3)
f3 / fw> 2.4 (Condition 4)
Here, f1 represents the focal length of the first lens unit L1, f3 represents the focal length of the third lens unit L3, and fw represents the focal length of the entire system at the wide angle end.

  When the upper limit of conditional expression (3) is exceeded and the power (refractive power) of the first lens unit L1 becomes too strong, it becomes difficult to correct coma around the screen in the wide angle range. If the power of the first lens unit L1 becomes too weak beyond the lower limit of the conditional expression (3), the total lens length and the effective diameter of the first lens unit L1 increase, which is not preferable.

  If the power of the third lens unit L3 is increased beyond the lower limit of conditional expression (4), the exit pupil position will move away from the image plane and the telecentricity will be improved, but spherical aberration and curvature of field will be corrected in a well-balanced manner. Therefore, it is difficult to secure a flat image surface, which is not preferable. On the other hand, if the power of the third lens unit L3 becomes too weak, the telecentric characteristics deteriorate, and the amount of movement increases when focusing with the third lens unit L3. As a result, the total lens length tends to increase. It is not preferable.

Therefore, it is more preferable that the numerical ranges of the conditional expressions (3) and (4) are set so as to satisfy the following conditional expressions (3a) and (3b).
−2.7 <f1 / fw <−2.3 (3a)
6.0> f3 / fw> 2.7 (4a)

  Examples 1-4 according to specific numerical values of the zoom lens will be described below.

In each numerical example, f represents a focal length, fno represents an F number, and ω represents a half angle of view. i indicates the order of the surfaces from the object side, ri is the radius of curvature of the i-th surface, di is the distance between the i-th surface and the (i + 1) -th surface, ni and νi are the refractive index and Abbe number for the d-line, respectively. Show. The two surfaces closest to the image side correspond to a crystal low-pass filter, an infrared cut filter, and the like, and are glass blocks G provided by design.
Further, the aspherical shape can be expressed by the following equation when the displacement in the optical axis direction at the position of the height H from the optical axis is X with respect to the surface vertex.

  Where R is the paraxial radius of curvature, K is the conic constant, A is the fourth order aspheric coefficient, B is the sixth order aspheric coefficient, C is the eighth order aspheric coefficient, and D is the tenth order. Represents the aspherical coefficient of each.

In each of Examples 1 to 4, surface numbers as shown in FIG. 2 were assigned to the lenses, the diaphragm SP, and the glass block G that constitute each lens group of the zoom lens 1.
Specifically, the object side surface (convex surface) of the negative lens 11 constituting the first lens unit L1 is No. 1, the opposite concave surface is No. 2, and the object side surface of the positive lens 12 of the first lens unit L1 is No. 1. No. 3, the image side is No. 4, the stop SP is No. 5, the aperture side (convex surface) of the positive lens 21 constituting the second lens unit L2 is No. 6, and the image side (positive surface) of the positive lens 21. No. 5 is the object side surface of the negative lens 22, No. 8 is the image side surface of the negative lens 22 (the object side surface of the negative lens 23 that is the cemented surface), No. 9 is the image side surface of the positive lens 23, and the third lens group The object side surface of the positive lens 31 of L3 is No. 10, the image side surface of the positive lens 33 is No. 11, the surface on the third lens unit L3 side of the glass block G is No. 12, and the image side IP side surface is No. 13. It is a turn.

Example 1
Tables 1 to 3 show the numerical values of Example 1. Each numerical value of Example 1 corresponds to the zoom lens 1 of FIG.
Table 1 shows the curvature radius (r: mm) and interval (d: mm), refractive index (n), Abbe number (ν) of each lens, diaphragm, and cover glass corresponding to each surface number of the zoom lens in Example 1. ).

  Table 2 shows aspheric coefficients of predetermined surfaces of the first lens unit L1, the second lens unit L2, and the third lens unit L3 including the aspherical surface in Example 1. In Table 2, K is the conic constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, C is the eighth-order aspheric coefficient, and D is the tenth-order aspheric coefficient. Represents.

  Table 3 shows numerical values of variable intervals and focal lengths of the surfaces 4, 9, and 11 whose intervals change with zooming.

3 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end in Example 1. FIG. 4 is a diagram illustrating spherical aberration, astigmatism at the intermediate zoom position in Example 1, and FIG. FIG. 5 is an aberration diagram showing spherical aberration, astigmatism, and distortion aberration at the telephoto end in Example 1. FIG. 3A to 5A show spherical aberration, FIG. 3B shows astigmatism, and FIG. 3C shows distortion. In FIG. 3 to FIG. 5B, ΔM represents the value of the d-line on the meridional image plane, and ΔS represents the value of the d-line on the sagittal image plane.
As can be seen from FIGS. 3 to 5, according to Example 1, the spherical, astigmatism, and distortion aberrations were corrected well at the focal position distance from the wide-angle end to the telephoto end, and the imaging performance was excellent. A zoom lens is obtained.

(Example 2)
Tables 4 to 6 show numerical values of Example 2. Each numerical value of Example 2 corresponds to the zoom lens 1A of FIG. A zoom lens 1A in FIG. 6 is a zoom lens having a zoom ratio (magnification ratio) of 2.8 times and an F number of 3.2 (wide-angle end) to 6.1 (telephoto end).
Table 3 shows the curvature radius (r: mm) and interval (d: mm), refractive index (n), Abbe number (ν) of each lens, diaphragm, and cover glass corresponding to each surface number of the zoom lens in Example 2. ).

  Table 5 shows aspheric coefficients of predetermined surfaces of the first lens unit L1, the second lens unit L2, and the third lens unit L3 including the aspherical surface in Example 2. In Table 5, K is the conic constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, C is the eighth-order aspheric coefficient, and D is the tenth-order aspheric coefficient. Represents.

  Table 6 shows numerical values of the variable interval and focal length of the surfaces 4, 9, and 11 in which the interval changes with zooming.

7 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end in Example 2. FIG. 8 is a diagram illustrating spherical aberration, astigmatism at the intermediate zoom position in Example 2, and FIG. FIG. 9 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end in the second embodiment. 7A to 9A show spherical aberration, FIG. 7B shows astigmatism, and FIG. 7C shows distortion. 7B to 9B, ΔM represents the value of the d-line on the meridional image plane, and ΔS represents the value of the d-line on the sagittal image plane.
As can be seen from FIG. 7 to FIG. 9, according to the second embodiment, various aberrations such as spherical, astigmatism, and distortion are well corrected at the focal position distance from the wide-angle end to the telephoto end, and the imaging performance is excellent. A zoom lens is obtained.

(Example 3)
Tables 7 to 9 show numerical values of Example 3. Each numerical value of Example 3 corresponds to the zoom lens 1B of FIG. The zoom lens 1B in FIG. 10 is a zoom lens having a zoom ratio (magnification ratio) of 2.7 times and an F number of 3.4 (wide-angle end) to 6.2 (telephoto end).
Table 7 shows the curvature radius (r: mm) and interval (d: mm), refractive index (n), Abbe number (ν) of each lens, diaphragm, and cover glass corresponding to each surface number of the zoom lens in Example 3. ).

  Table 8 shows aspheric coefficients of predetermined surfaces of the first lens unit L1, the second lens unit L2, and the third lens unit L3 including the aspherical surface in Example 3. In Table 8, K is a conic constant, A is a fourth-order aspheric coefficient, B is a sixth-order aspheric coefficient, C is an eighth-order aspheric coefficient, and D is a tenth-order aspheric coefficient. Represents.

  Table 9 shows numerical values of variable intervals and focal lengths of the surfaces 4, 9, and 11 whose intervals change with zooming.

FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end in Example 3. FIG. 12 shows spherical aberration, astigmatism at the intermediate zoom position in Example 3, and FIG. 13 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end in Example 3. 11A to 13A show spherical aberration, FIG. 11B shows astigmatism, and FIG. 13C shows distortion. 11B, ΔM represents the value of the d-line on the meridional image plane, and ΔS represents the value of the d-line on the sagittal image plane.
As can be seen from FIGS. 11 to 13, according to Example 3, various aberrations such as spherical, astigmatism, and distortion were corrected well at the focal position distance from the wide-angle end to the telephoto end, and the imaging performance was excellent. A zoom lens is obtained.

Example 4
Tables 10 to 12 show numerical values of Example 4. Each numerical value of Example 4 corresponds to the zoom lens 1C of FIG. The zoom lens 1 </ b> C in FIG. 10 is a zoom lens having a zoom ratio (magnification ratio) of 2.8 times and an F number of 3.3 (wide-angle end) to 6.0 (telephoto end).
Table 10 shows the curvature radius (r: mm) and interval (d: mm), refractive index (n), Abbe number (ν) of each lens, stop, and cover glass corresponding to each surface number of the zoom lens in Example 4. ).

  Table 11 shows aspheric coefficients of predetermined surfaces of the first lens unit L1, the second lens unit L2, and the third lens unit L3 including the aspherical surface in Example 4. In Table 11, K is a conic constant, A is a fourth-order aspheric coefficient, B is a sixth-order aspheric coefficient, C is an eighth-order aspheric coefficient, and D is a tenth-order aspheric coefficient. Represents.

  Table 12 shows the numerical values of the variable distance and the focal length of the surfaces 4, 9, and 11 whose distances change with zooming.

FIG. 15 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end in Example 4. FIG. 16 shows spherical aberration, astigmatism at the intermediate zoom position in Example 4, and FIG. 17 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end in Example 4. (A) of FIGS. 15 to 17 shows spherical aberration, (B) shows astigmatism, and (C) shows distortion. In FIG. 15 to FIG. 17B, ΔM indicates the value of the d line on the meridional image plane, and ΔS indicates the value of the d line on the sagittal image plane.
As can be seen from FIGS. 15 to 17, according to Example 4, the spherical, astigmatism, and distortion aberrations are well corrected at the focal position distance from the wide-angle end to the telephoto end, and the imaging performance is excellent. A zoom lens is obtained.

Table 13 is a diagram showing specific values of the conditional expressions (19 to (4)) of the zoom lens according to Examples 1 to 4 described above.
As is apparent from Table 13, the above conditional expressions (19 to (4)) of the zoom lenses according to Examples 1 to 4 are sufficiently satisfied.

  According to the zoom lens of the present embodiment described above, the zoom ratio is about 2 to 3 times, which is suitable for an imaging system using a solid-state imaging device, is compact with a small number of constituent lenses, and particularly suitable for a retractable zoom lens. A zoom lens having excellent optical performance can be realized.

  Further, by effectively introducing an aspheric surface into a predetermined lens group, in particular, by introducing one or more aspheric surfaces into the second lens group L2, various off-axis aberrations, particularly astigmatism, distortion, and large aberrations. It is possible to effectively correct spherical aberration when the aperture ratio is made.

  In other words, the zoom lens according to the present embodiment can reduce the number of components of each lens group, and can achieve a reduction in size by reducing the amount of movement of the zoom lens group while ensuring a desired zoom ratio. . Moreover, the desired telecentricity can be maintained.

The zoom lenses 1, 1 </ b> A to 1 </ b> C having the characteristics as described above can be applied to imaging devices with strict restrictions on the overall length, such as digital still cameras, imaging cameras equipped with imaging devices, and cameras equipped with portable information terminals.
In particular, since it has a suitable overall lens length and high optical performance that can be mounted on a mobile phone or the like, it is suitable for a digital input device (camera (optical) module).

  18 and 19 are external perspective views showing an embodiment of a mobile phone equipped with a camera (optical) module employing the imaging lens according to the present embodiment. The mobile phone 100 is configured as a so-called foldable mobile phone. FIG. 18 shows an open state, and FIG. 19 shows a closed state.

  The mobile phone 100 includes a receiving case 101 and a transmitting case 102, and the receiving case 101 and the transmitting case 102 are connected to each other by a connecting unit 103 so as to be opened and closed. The receiving case 101 and the transmitting case 102 include front side cases 101c and 102c on the surfaces (front sides) facing each other in the closed state, and back side cases 101d and 102d on the back side. These cases are integrally formed of, for example, resin.

  The receiving case 101 is provided with a main display unit 104 that displays an image on the front side and a sub display unit 105 that displays an image on the back side along each surface. The main display unit 104 and the sub display unit 105 are configured by, for example, a liquid crystal display. In addition, the receiver case 101 is provided with an optical module 106 for imaging a subject from an opening 101e provided in the back side case 101d, and a strobe 107 that emits light from the back side.

  The transmitter case 102 includes an operation unit 108 on the front side. Various buttons for operating the cellular phone 100 such as a numeric keypad button 108a are arranged on the operation unit 108. The cellular phone 100 performs radio communication and imaging by the optical module 106 in response to an input operation to the numeric keypad 108a.

The mobile phone 100 is provided with a high-frequency circuit for radio communication, an antenna, a microphone and a speaker for telephone call, which are not shown.
Similarly, although not shown, a cover is provided on the opposite surface of the operation unit 108, and when the cover is opened, a battery storage unit is provided, and a battery as a power supply unit is stored.
In the present embodiment, power is supplied from the battery to the drive source of the optical module 106, thereby reducing the number of components and reducing the size of the mobile phone 100.

As described above, the optical module 106 employs the zoom lenses 1 and 1A to 1C according to the present embodiment.
Hereinafter, a configuration example of the optical module will be described with reference to FIGS. 20 (A), (B), FIG. 21, and FIGS. 22 (A) to (C).

20A and 20B are external perspective views of the camera module 106 according to the embodiment, in which FIG. 20A is a perspective view with the exterior cover 201 hung, and FIG. 20B is a perspective view with the exterior cover 201 removed. The camera module 106 is, for example, about 10 to 12 mm in width, about 20 to 24 mm in height, and 15 in length so that it can be incorporated into a mobile terminal such as a mobile phone with the exterior cover 201 shown in FIG. The size is about ˜20 mm and enables continuous zooming and autofocus.
In the figure, 202 is an object side optical lens, 203 is an image sensor using a CCD (Charge Coupled Device), etc., an image sensor unit equipped with a control circuit such as a zoom and autofocus motor and shutter, and 204 is a camera module. A main body, 205 is a cover for shielding the optical system accommodated therein, and 206 is a main flexible board.
The main flexible board 206 is provided to exchange signals between the camera module 106 and the portable terminal 100 that houses the camera module 106 and to supply power to the camera module 106.

  FIG. 21 is a configuration diagram illustrating a lens group constituting the camera module 106 of the embodiment and a mechanism for moving a lens holding frame that accommodates the lens group in the optical axis direction.

In the camera module 106, as shown in FIG. 21, the subject-side first lens group L1 is housed in the first lens holding frame 211, and the second lens group L2 is housed in the second lens holding frame 212.
A shutter unit 213 is attached to the second lens holding frame 212 that accommodates the second lens group L2, and the shutter unit 213 and the second lens holding frame 212 are formed to move together.
The third lens group L3 for focusing is housed in the third lens holding frame 214.
In the camera module 106 according to this embodiment, the second lens unit L2 integrated with the first lens unit L1 and the shutter unit 213 moves in the optical axis direction to perform continuous change in focal length, that is, zooming. In order to correct the focus position changed by the zooming, the third lens unit L3 moves simultaneously.

Here, before describing the lens moving mechanism in FIG. 21, an outline of an optical system used in the camera module 106 according to the embodiment will be described with reference to FIG.
In FIG. 22, (A) is a cross-sectional view showing the relationship between the lenses constituting each of the lens groups and the image sensor, and (B) is a diagram showing the positional relationship of each lens group in a wide angle (Wide) state. (C) is the figure which showed the positional relationship of each lens group in the state of telephoto (Tele).

  The optical system in the camera module 106 according to the present embodiment includes the subject-side first lens group L1 housed in the first lens holding frame 211 and the second lens group L2 housed in the second lens holding frame 212 as described above. And the third lens unit L3 accommodated in the third lens holding frame 214, and the zooming cam moves the first lens unit L1 and the second lens unit L2 in the optical axis direction to perform zooming. The third lens unit L3 is moved and focused by an autofocus cam corresponding to the focus position changed by zooming, and an image is formed on the image sensor 216 provided on the image sensor unit substrate 215. It has become. Further, a shutter unit 213 equipped with a diaphragm 2131 and shutter blades 2132 is provided on the first lens group L3 side in the second lens group L2.

  In this optical system, for example, the first lens group L1 is a plurality of plastic lens groups having negative power (diffuse light), and the second lens group L2 is a plurality of glass lenses having positive power (condensation). The third lens group L3 is composed of a single plastic lens so that the length from the first surface of the lens to the focal point can be shortened, and the first lens group L1 and the third lens group L3. The moving range in the optical axis direction of the second lens unit L2 sandwiched between the first lens unit L2 and the third lens unit L3 is designed to be larger than the moving range in the optical axis direction of the first lens unit L1 and the third lens unit L3.

For this reason, as can be seen from FIGS. 22B and 22C, the light beam incident on the second lens unit L2 is the most constricted state in both the wide angle (Wide) and the telephoto (Tele). Further, the second lens group L2 has the largest movement range among the three lens groups, but a certain amount of space can be secured on both the subject side and the image sensor side. Therefore, by installing the diaphragm 2131 and the shutter 2132 so as to be integrated with the second lens unit L2, it is possible to install the diaphragm 2131 and the shutter 2132 without increasing the maximum aperture.
Further, compared with the case where the shutter unit 213 is further provided on the subject side of the first lens unit L1, the height of the optical system in the optical axis direction can be lowered by the amount of the shutter unit 213, and the camera module 106 can be made smaller accordingly. In addition, the driving force for opening and closing the shutter 2132 and the aperture 2131 is small.

The second lens holding frame 212 that houses the second lens group L2 has a small diameter on the subject side of the second lens group L2, and the shutter unit 213 has a small diameter on the second lens holding frame 212 side. An outer peripheral wall that is a concave portion is formed on the second lens group L2 side so as to engage with the second lens group L2 side peripheral wall that is convex toward the subject side.
Therefore, the shutter unit 213 can be engaged with and fixed to the second lens holding frame 212 so as not to be eccentric.
As the shutter unit 213, a commonly used shutter unit can be used as long as it has a structure in which a plurality of blades are opened and closed using an actuator or the like. In the above description, the case where the second lens holding frame 212 is provided on the subject side has been described as an example. However, the imaging element unit 203 side of the second lens holding frame 212 may be similarly configured and provided. Of course.

  The first lens group L1, the second lens group L2, and the third lens group L3 are configured so that the first lens group L1 and the third lens group L3 are subjects in the wide-angle state shown in FIG. The second lens unit L2 is closer to the image sensor 216 side. Further, in the telephoto state shown in FIG. 22C, the image pickup element 216 is slightly as shown by d in the first lens unit L1 than in the wide-angle state shown in FIG. 22B. If the third lens group L3 moves to the image sensor 216 side, the second lens group L2 moves largely to the subject side.

The above is the configuration of the optical system. Hereinafter, the lens group moving mechanism will be described with reference to FIG. 21 again.
The first lens holding frame 211, the second lens holding frame 212, and the third lens holding frame 214, which respectively accommodate the first lens group L1, the second lens group L2, and the third lens group L3, are respectively provided in the first lens holding frame. A bearing portion 221, a second lens holding frame bearing portion and a third lens holding frame bearing portion 222 not shown in FIG. 2 are provided.
The first lens holding frame bearing portion 221 and the third lens holding frame bearing portion 222 are inserted into the first guide shaft 223, and the second lens holding frame bearing portion (not shown) is different from the first guide shaft 223. The second guide shaft 224 is inserted into the second guide shaft 224, and a bearing portion provided on the substantially opposite side to the bearing portion of each lens holding frame is inserted through the third guide shaft 225 and guided to move in the optical axis direction. It is formed as follows.
The first lens holding frame bearing portion 221, the second lens holding frame bearing portion (not shown), and the third lens holding frame bearing portion 222 are aligned so that their lengths in the optical axis direction are substantially the same. Consideration is made so that the inclination of the holding frame with respect to the guide shaft is the same.

Each of the first to third lens holding frame bearing portions 221 and 222 includes a first lens holding frame cam follower 226, a second lens holding frame cam follower and a third lens holding frame not shown in FIG. A cam follower 227 is provided.
These cam followers are used for the first lens group cam surface 232 and the second lens group of the first zoom cam 231 constituting the zoom cam 230 provided to face the first guide shaft 223 and the second guide shaft 224. The cam surface 233, the second lens group cam surface 235 of the second zoom cam 234, and the third lens group cam surface 241 of the autofocus cam 240 are in contact with the zoom cam 230 and the autofocus cam 240, respectively. The first to third lens holding frame bearing portions 221 and 222 are moved in the direction of the optical axis by the rotation of.

The third guide shaft 225 serves to prevent the rotation of the lens holding frame bearing portions 221 to 222, and to move the lens holding frame in the optical axis direction with respect to the optical axis. The first guide shaft 223 and the second guide shaft 224 are provided on substantially opposite sides.
In addition, the first guide shaft 223 and the second guide shaft 224 are configured such that the third guide shaft 225 is parallel to the optical axis of the optical system, and the first guide shaft 223 and the second guide shaft 224 are zoomed. The cams 230 and the autofocus cams 240 are arranged at concentric positions with respect to the cam shaft centers and spaced apart from each other by a predetermined angle. The shaft centers of the third guide shaft 225, the first guide shaft 223, and the second guide shaft 224 are arranged. Is arranged so as to be a substantially isosceles triangle.

  Further, as shown in FIG. 21, the first lens holding frame bearing portion 221 and the third lens holding frame bearing portion 222 inserted through the first guide shaft 223 have an end portion around the first lens holding frame. A coil spring 250 is wound around the cam follower 226 and the third lens holding frame cam follower 227, and a force is applied in a direction that attracts each other.

The zoom cam 230 includes a first zoom cam 231 and a second zoom cam 234, and the second lens group cam surface 233 of the first zoom cam 231 and the second zoom cam 234. The second lens group cam surface 235 in FIG. 2 is a substantially equivalent cam surface, and a second lens holding frame cam follower not shown in FIG. 2 is sandwiched between the cam surfaces.
Therefore, a force is applied in the direction in which the first lens holding frame bearing portion 221 and the third lens holding frame bearing portion 222 are attracted to each other by the spring 250, so that the autofocus cam 240 is not illustrated. The zoom cam 234 is pushed toward the first zoom cam 231, and the second lens group cam surface 235 and the second lens group cam surface 233 hold the second lens holding frame cam follower (not shown) firmly. The three cam followers come into contact with the corresponding cam surfaces without rattling.

  As described above, since the relative movement amount of the first lens unit L1 and the third lens unit L3 is smaller than the movement amount of the second lens unit L2, the tensile force of the coil spring 250 may change greatly. Absent. Therefore, the contact force of the first lens holding frame cam follower 226 and the third lens holding frame cam follower 227 to the cam surfaces 232 and 241 is a movement of the first lens unit L1 and the third lens unit L3 due to a change in focal length and focusing. At this time, since there is no significant change, zooming and focusing can always be performed with a constant driving force.

In the example of FIG. 21, the spring 250 is applied in the direction in which the first lens unit L1 and the third lens unit L3 are brought closer to each other. However, the first lens unit cam surface 232 of the zoom cam 230 and the autofocus cam The third lens group cam surface 241 of 240 is provided so that the contact directions of the first lens holding frame cam follower 226 and the third lens holding frame cam follower 227 are reversed, so that the first lens group L1 and the third lens are provided. It is good also as a spring of the direction which mutually separates the group L3.
However, in this case, it is necessary to separately apply a force that causes the second lens holding frame cam follower (not shown in FIG. 21) to always contact the corresponding cam surface with a constant force.

  The zoom cam 230 and the auto focus cam 240 are connected to a zoom gear group 260, a zoom gear 270, an auto focus gear group 280, and an auto focus motor from a zoom motor and an auto focus motor (not shown). A driving force is transmitted through the gear 290 so that it can rotate.

As described above, the zoom lenses 1 and 1A to 1C according to the present embodiment can be easily mounted on an imaging device with strict total length restrictions such as a digital still camera using an imaging element, a camera mounted on a mobile phone, or a camera mounted on a portable information terminal. is there.
In addition, the zoom lenses 1 and 1A to 1C have high optical performance as well as having a suitable overall lens length that can be mounted on a mobile phone or the like, so that a highly accurate image can be obtained. is there.

It is a figure which shows the basic composition of the zoom lens of this embodiment. In Examples 1-4, it is a figure which shows the surface number provided with respect to each lens which comprises each lens group of a zoom lens, an aperture_diaphragm | restriction, and a glass block. In Example 1, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion in the intermediate zoom position in the first embodiment. FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end in Example 1. 6 is a diagram illustrating a configuration of a zoom lens employed in Example 2. FIG. In Example 2, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. In Example 2, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate zoom position. In Example 2, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. 6 is a diagram illustrating a configuration of a zoom lens employed in Embodiment 3. FIG. In Example 3, it is an aberrational figure which shows the spherical aberration, astigmatism, and a distortion aberration in a wide angle end. In Example 3, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in an intermediate zoom position. In Example 3, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. 6 is a diagram illustrating a configuration of a zoom lens employed in Example 4. FIG. In Example 4, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. FIG. 9 is an aberration diagram showing spherical aberration, astigmatism, and distortion in the intermediate zoom position in Example 4. In Example 4, it is an aberrational figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. It is an external appearance perspective view which shows one Embodiment of the mobile phone carrying the camera (optical) module which employ | adopted the imaging lens which concerns on this embodiment, Comprising: It is a figure which shows an open state. It is an external appearance perspective view which shows one Embodiment of the mobile telephone carrying the camera (optical) module which employ | adopted the imaging lens which concerns on this embodiment, Comprising: It is a figure which shows a closed state. It is an external appearance perspective view of the camera module of this embodiment. It is the block diagram which showed the lens group which comprises the camera module of this embodiment, and the mechanism which moves the lens holding frame which accommodated the lens group to an optical axis direction. It is a figure for demonstrating the relationship between the lens which comprises each of the lens group of the camera module of this embodiment, and an image pick-up element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A-1C ... Zoom lens L1 ... 1st lens group 11 ... Negative lens 12 ... Positive lens L2 ... 2nd lens group 21 ... Positive lens 22 ... Negative lens DESCRIPTION OF SYMBOLS 23 ... Negative lens L3 ... 3rd lens group 31 ... Positive lens SP ... Aperture stop G ... Glass block IP ... Image surface 100 ... Mobile phone 106 ... Optical module

Claims (13)

A zoom lens having an imaging optical system having a zooming function for an imaging element,
The imaging optical system is arranged in order from the object side,
A first lens unit having a negative refractive power;
A second lens unit having a positive refractive power;
A third lens group having a positive refractive power,
The second lens group includes three lenses, and includes at least one positive lens and at least one negative lens. Three lenses in the second lens group are cemented. A zoom lens that has been formed. The zoom lens according to claim 1, wherein at least one surface of the lens in the second lens group is an aspherical surface. The zoom lens according to claim 1, wherein the second lens group is formed of a cemented lens of a positive lens, a first negative lens, and a second negative lens in order from the object side. The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression (1) is satisfied, where f2 is a focal length of the second lens group and fw is a focal length of the entire system at the wide-angle end.
1.3 <f2 / fw <2.1 (1) The lens arranged closest to the image side of the second lens group is a meniscus negative lens having an aspheric surface on the image side and a convex surface facing the object side, and the radius of curvature of the object side surface is Ra. The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression (2) is satisfied, where fw is a focal length of the entire system at the wide-angle end.
1.25 <Ra / fw <15 (2) The lens arranged closest to the image side of the second lens group is a meniscus negative lens having an aspheric surface on the image side and a convex surface facing the object side, and the aspheric surface shape is a periphery from the center of the optical axis. The zoom lens according to claim 1, wherein the zoom lens is an aspheric surface in which negative refractive power is stronger than a spherical shape toward the surface. When the focal length of the first lens group is f1, the focal length of the third lens group is f3, and the focal length of the entire system at the wide angle end is fw, the following conditional expressions (3) and (4) are satisfied. The zoom lens according to claim 1.
−3.0 <f1 / fw <−1.9 (3)
f3 / fw> 2.4 (4) During zooming from the wide-angle end to the telephoto end, the first lens unit moves along a convex locus toward the image side, the second lens unit moves monotonously toward the object side, and the third lens unit moves toward the image side. The zoom lens according to any one of claims 1 to 7. The zoom lens according to claim 1, wherein the first lens group includes two lenses, a negative lens and a positive lens. The first lens group includes, in order from the object side to the image side, two lenses, a negative lens having a concave surface on both sides and a meniscus positive lens having a convex surface on the object side. A zoom lens according to any one of the above. A zoom lens having an imaging optical system having a zooming function for the imaging element;
A lens holder for holding the zoom lens,
The imaging optical system is arranged in order from the object side,
A first lens unit having a negative refractive power;
A second lens unit having a positive refractive power;
A third lens group having a positive refractive power,
The second lens group includes three lenses, and includes at least one positive lens and at least one negative lens. Three lenses in the second lens group are cemented. An optical module that has been formed. An optical module;
A housing for housing the optical module;
The optical module is
A zoom lens having an imaging optical system having a zooming function for the imaging element;
A lens holder for holding the zoom lens,
The imaging optical system is arranged in order from the object side,
A first lens unit having a negative refractive power;
A second lens unit having a positive refractive power;
A third lens group having a positive refractive power,
The second lens group includes three lenses, and includes at least one positive lens and at least one negative lens. Three lenses in the second lens group are cemented. A mobile terminal that has been formed. Having power supply means,
The portable terminal according to claim 12, wherein the optical module is supplied with power by the power supply means.

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