JP2005301031A - Zoom lens having synthetic resin lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens having synthetic resin lens capable of responding to higher pixel density, which is suitable for the mounting, particularly to small-sized information terminal devices and is low-cost and compact. <P>SOLUTION: The zoom lens having synthetic resin lens is provided with a negative first moving group 11, a positive second moving group 12 and a positive rear-side fixed group 13. The first moving group 11 has a negative refractive power as a whole and is constituted with a first moving lens G1 of a negative refractive power, having an aspheric surface and a second moving lens G2 having a positive refractive power. The second moving group 12 has a positive refractive power as a whole and is constituted with a third moving lens G3 which has an aspheric surface, faces a convex face toward the object side on the paraxial neighborhood and has a positive refractive power and a fourth moving lens G4, which has a negative refractive power and has a biconcave shape, in the order from the object side. The rear-side fixed group 13 is constituted with only one rear-side fixed lens G5 which has a positive refractive power and has a biconvex shape. The synthetic resin lens is arranged on at least one side of the first and second moving groups 11, 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens having a synthetic resin lens (plastic lens) suitable for mounting on a small information terminal device such as a camera-equipped mobile phone or a PDA (Personal Digital Assistant).

  In recent years, with the spread of personal computers to ordinary homes and the like, digital still cameras (hereinafter simply referred to as digital cameras) capable of inputting image information such as photographed landscapes and human images to personal computers have rapidly spread. It's getting on. As mobile phones become more sophisticated, camera-equipped mobile phones equipped with a small imaging module are also rapidly spreading. In addition, small information terminal devices such as PDAs that are equipped with an imaging module have become widespread.

  In devices equipped with these imaging functions, imaging devices such as a charge coupled device (CCD) and a complementary metal oxide semiconductor (CMOS) are used. In recent years, these image sensors have been extremely reduced in size and increased in pixels, and accordingly, the main body of the image pickup apparatus and the lens mounted thereon are also required to have a compact configuration with high resolution performance. Yes. For example, camera-equipped mobile phones and the like that are compatible with megapixels of 1 million pixels or more have been put into practical use, and the demand for performance has been increasing.

  By the way, there are an optical zoom method and an electronic zoom method as a method for realizing a zoom function in an imaging device using an image sensor. In the optical zoom system, a zoom lens is mounted as a photographing lens, and the photographing magnification is optically changed. The electronic zoom method electronically changes the size of a subject image by trimming an image by signal processing. In general, the optical zoom method can obtain higher resolution performance than the electronic zoom method. Therefore, when zooming with high resolution performance, the optical zoom method is preferable.

Conventionally, as a relatively small zoom lens used for a digital camera or the like, for example, there is a lens described in Patent Document 1 below. Patent Document 1 describes a zoom lens of a two-group zoom system that is composed of five or six lenses as a whole.
JP 2003-270533 A

  In small information terminal devices such as camera-equipped mobile phones, conventionally, fixed-focus lenses are generally used in terms of cost and miniaturization, but with the recent increase in functionality and multifunction, There is a demand for a zoom function. Therefore, recently, some mobile phones with cameras using fixed focus lenses have realized a zoom function by adopting an electronic zoom method. However, in the case of the electronic zoom method, the resolution deteriorates as the image enlargement ratio increases, and it has become difficult to cope with the recent increase in the number of pixels of the image sensor.

  Therefore, it is conceivable that a camera-equipped mobile phone or the like is equipped with a zoom lens and adopts an optical zoom system. In this case, using a high-performance zoom lens developed for a conventional digital camera as it is is not practical in terms of cost and compactness. Although the zoom lens described in Patent Document 1 is also reduced in size with a relatively small number of lenses for a digital camera, it is further reduced in size when used in a small information terminal device. It is preferable that the cost is reduced. On the other hand, a low-cost and compact zoom lens composed of about three lenses has been developed in the past, but this makes it difficult to cope with an increase in the number of pixels.

  The present invention has been made in view of such problems, and an object of the present invention is to realize a low-cost and compact zoom optical system that is suitable for mounting in a small information terminal device, while corresponding to an increase in the number of pixels. Another object is to provide a zoom lens having a synthetic resin lens.

A zoom lens having a synthetic resin lens according to the first aspect of the present invention includes at least one fixed group that is fixed during zooming and a strong refractive power that moves on the optical axis during zooming and is relatively strong with respect to the fixed group. And first and second moving groups. The first moving group has a negative refractive power as a whole. The second moving group has a positive refractive power as a whole, and in order from the object side, has a positive refractive power lens having an aspheric surface and a convex surface facing the object side in the vicinity of the paraxial axis, and a negative refractive power. And a biconcave lens. Further, at least one of the first and second moving groups has a synthetic resin lens.
Furthermore, it is comprised so that the following conditional expressions may be satisfied.
4.0 <Tw / fw <6.0 (1)
1.1 <f2g / fw <1.5 (2)
Where fw is the focal length of the entire system at the wide-angle end, Tw is the conjugate distance (full length) at the wide-angle end, and f2g is the focal length of the second moving group.

  In the zoom lens having the synthetic resin lens according to the first aspect of the present invention, the fixed group can be arranged, for example, on the most image side or on both the most object side and the most image side.

A zoom lens having a synthetic resin lens according to the second aspect of the present invention includes a rear fixed group that is fixed at the time of zooming and is disposed closest to the image side, and moves on the optical axis during zooming, and is a rear fixed group. The first and second moving groups having relatively strong refractive power. The first moving group has a negative refractive power as a whole, and is composed of a first moving lens having a negative refractive power having an aspheric surface and a second moving lens having a positive refractive power in order from the object side. Has been. The second moving group has a positive refractive power as a whole, and in order from the object side, has a third moving lens with a positive refractive power having an aspheric surface and a convex surface facing the object side in the vicinity of the paraxial axis, and a negative moving power. And a fourth moving lens having a biconcave shape having a refractive power of 2 mm. The rear fixed group is composed of only one biconvex lens having positive refractive power. Further, at least one of the first and second moving groups has a synthetic resin lens.
Furthermore, it is comprised so that the following conditional expressions may be satisfied.
4.0 <Tw / fw <5.0 (1A)
1.1 <f2g / fw <1.4 (2A)
Where fw is the focal length of the entire system at the wide-angle end, Tw is the conjugate distance (full length) at the wide-angle end, and f2g is the focal length of the second moving group.

The zoom lens according to the second aspect is preferably configured so as to satisfy the following conditional expression. Here, f3 is the focal length of the third moving lens, f4 is the focal length of the fourth moving lens, ν3 is the Abbe number of the third moving lens, and ν4 is the Abbe number of the fourth moving lens.
| F3 / ν3 + f4 / ν4 | / fw <0.05 (3A)
In this case, it is preferable that the following conditional expression is satisfied.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.08 (5A)
Here, f5 represents the focal length of the lens constituting the rear fixed group, and ν5 represents the Abbe number of the lens constituting the rear fixed group.

The zoom lens according to the second aspect is preferably configured to satisfy the following conditional expression with respect to the center thickness DG4 of the fourth moving lens.
0.45 <DG4 / fw <0.7 (4A)

In the zoom lens according to the second aspect, when the lens constituting the rear fixed group is a glass lens, it is preferably configured to satisfy the following conditional expression. However, NG5 shows the refractive index of the lens which comprises a back side fixed group.
NG5> 1.70 (6)
In this case, it is preferable that the following conditional expression is satisfied.
ν3−ν4> 20 (7)
Here, ν3 represents the Abbe number of the third moving lens, and ν4 represents the Abbe number of the fourth moving lens.

  In the zoom lens according to the second aspect, for example, the first moving lens may be composed of a synthetic resin lens, and the third moving lens may be composed of a glass lens.

  In the zoom lens according to the second aspect, for example, both the first moving lens and the lens constituting the rear fixed group may be made of a synthetic resin lens.

A zoom lens having a synthetic resin lens according to a third aspect of the present invention includes a front fixed group that is fixed at the most object side during zooming and a rear fixed group that is fixed at the most image side during zooming. And a first moving group and a second moving group that move on the optical axis during zooming and have relatively strong refractive power with respect to the front fixed group and the rear fixed group. The front fixed group is composed of only one meniscus lens. The first moving group has a negative refractive power as a whole, and is composed of a first moving lens having a negative refractive power having an aspheric surface and a second moving lens having a positive refractive power in order from the object side. Has been. The second moving group has a positive refractive power as a whole, and in order from the object side, a third moving lens having a positive refractive power having an aspheric surface and a convex surface facing the object side in the vicinity of the paraxial axis, And a fourth moving lens having a biconcave shape having a refractive power of 2 mm. The rear fixed group is composed of only one biconvex lens having positive refractive power. At least the first moving group has a lens made of synthetic resin.
Furthermore, it is comprised so that the following conditional expressions may be satisfied.
4.0 <Tw / fw <6.0 (1)
1.1 <f2g / fw <1.45 (2B)
Where fw is the focal length of the entire system at the wide-angle end, Tw is the conjugate distance (full length) at the wide-angle end, and f2g is the focal length of the second moving group.

The zoom lens according to the third aspect is preferably configured so as to satisfy the following conditional expression. Here, f3 is the focal length of the third moving lens, f4 is the focal length of the fourth moving lens, ν3 is the Abbe number of the third moving lens, and ν4 is the Abbe number of the fourth moving lens.
| F3 / ν3 + f4 / ν4 | / fw <0.04 (3B)
In this case, it is preferable that the following conditional expression is satisfied.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.05 (5B)
Here, f5 represents the focal length of the lens constituting the rear fixed group, and ν5 represents the Abbe number of the lens constituting the rear fixed group.

The zoom lens according to the third aspect is preferably configured so as to satisfy the following conditional expression with respect to the center thickness DG4 of the fourth moving lens.
0.5 <DG4 / fw <0.75 (4B)

In the zoom lens according to the third aspect, when the lens constituting the rear fixed group is a glass lens, it is preferably configured to satisfy the following conditional expression. However, NG5 shows the refractive index of the lens which comprises a back side fixed group.
NG5> 1.70 (6)
In this case, it is preferable that the following conditional expression is satisfied.
ν3−ν4> 20 (7)
Here, ν3 represents the Abbe number of the third moving lens, and ν4 represents the Abbe number of the fourth moving lens.

  In the zoom lens according to the third aspect, for example, the first moving lens may be formed of a synthetic resin lens, and the third moving lens may be formed of a glass lens.

  In the zoom lens according to the third aspect, for example, both the first moving lens and the lens constituting the rear fixed group may be made of a synthetic resin lens.

  In the zoom lens according to the first to third aspects of the present invention, zooming is performed by moving the first and second moving groups on the optical axis. Focus adjustment may be performed in a fixed group, but it is advantageous to use at least one of the first and second movement groups as a movement group for focus adjustment in terms of reducing the number of movement groups. This is preferable because it is advantageous in terms of mechanical strength and fastness.

  In the zoom lens according to the first to third aspects of the present invention, cost reduction is achieved by using a lens made of synthetic resin. In order to further shorten the overall length, an aspheric lens is used. In addition to these, by satisfying the predetermined conditional expression and making the power distribution appropriate, for example, a compact optical system having a shorter overall length than the zoom lens having the five-element structure described in Patent Document 1 is realized. Is done.

  In particular, in the zoom lens according to the second aspect of the present invention, the cost is reduced and the size is reduced by using a relatively small number of lenses in a three-group five-lens configuration. Furthermore, by appropriately adopting the above-described preferable conditions as necessary, it is further advantageous for correction of aberrations, and a high-performance zoom optical system corresponding to an increase in the number of pixels can be obtained.

  In particular, in the zoom lens according to the third aspect, a brighter performance is obtained by increasing the number of lenses in the three-group six-lens configuration, for example, as compared to the five-lens zoom lens described in Patent Document 1. In addition, the aberration is corrected well. In particular, since the front fixed group is disposed closest to the object side, it becomes easier to widen the angle than when the front fixed group is not disposed. Furthermore, by appropriately adopting the above-described preferable conditions as necessary, it is further advantageous for correction of aberrations, and a high-performance zoom optical system corresponding to an increase in the number of pixels can be obtained.

  According to the zoom lens having a synthetic resin lens according to the first to third aspects of the present invention, an aspherical lens or a synthetic resin lens is appropriately used, and power distribution and the like are appropriately satisfied by satisfying each conditional expression. Therefore, it is possible to realize a low-cost and compact zoom optical system that is suitable for mounting on a small information terminal device, while corresponding to the increase in the number of pixels.

  In particular, according to the zoom lens according to the second aspect, since it is configured with a relatively small number of lenses as a three-group five-lens configuration, a zoom optical system excellent in cost reduction and compactness can be realized.

  In particular, according to the zoom lens according to the third aspect, since the front fixed group is disposed closest to the object side, it is possible to realize a zoom optical system that can easily widen the angle compared to the case where the front fixed group is not disposed.

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

[First Embodiment]
FIG. 1 shows a configuration example of a zoom lens according to the first embodiment of the present invention. This configuration example corresponds to the lens configuration of a first numerical example (FIGS. 7A and 7B) described later. FIG. 1 shows the lens arrangement at the wide angle end.

  In FIG. 1, the reference symbol Ri is the i-th component (i.e., the first component surface, including the aperture stop St), which is increased sequentially toward the image side (imaging side). The radius of curvature of the surface of i = 1 to 13) is shown. The symbol Di indicates the surface interval on the optical axis Z1 between the i-th surface and the i + 1-th surface.

  This zoom lens is particularly suitable for mounting on an imaging device using a small imaging device, for example, a small information terminal device such as a mobile phone with a camera. This zoom lens includes a first group (first moving group) 11 having a negative refractive power as a whole and a second group (second moving group) 12 having a positive refractive power as a whole along the optical axis Z1. And a third group (rear side fixed group) 13 having a positive refractive power as a whole. An aperture stop St is provided on the object side of the second moving group 12. The first moving group 11 and the second moving group 12 have a relatively strong refractive power with respect to the rear fixed group 13. At least one of the first moving group 11 and the second moving group 12 has a lens made of synthetic resin.

  An imaging element such as a CCD (not shown) is disposed on the imaging surface (imaging surface) Simg of the zoom lens. Various optical members may be arranged between the rear fixed group 13 that is the final lens group and the imaging surface Simg, depending on the configuration on the camera side where the lens is mounted. In the illustrated configuration example, a cover glass GC for protecting the imaging surface Simg is disposed. In addition, an optical member such as an infrared cut filter or a low-pass filter may be disposed.

  This zoom lens is a two-group zoom system, and zooming is performed by moving the first moving group 11 and the second moving group 12 on the optical axis. As the first moving group 11 and the second moving group 12 are zoomed from the wide-angle end to the telephoto end, the first moving group 11 and the second moving group 12 move so as to draw a locus indicated by a solid line in FIG. The focus adjustment is performed, for example, by extending the first movement group 11 alone or both the first movement group 11 and the second movement group 12 to the front side during short-distance shooting.

  The first moving group 11 includes a first moving lens G1 and a second moving lens G2. The first moving lens G1 is composed of an aspheric lens having at least one aspheric surface and has negative refractive power. The first moving lens G1 is preferably composed of a synthetic resin lens. The first moving lens G1 has, for example, a biconcave shape in the vicinity of the paraxial. The second moving lens G2 has a positive refractive power. The second moving lens G2 is, for example, a positive meniscus spherical lens having a convex surface facing the object side.

  The second moving group 12 includes a third moving lens G3 and a fourth moving lens G4. The third moving lens G3 is an aspheric lens having at least one aspheric surface. The third moving lens G3 has a positive refractive power, has a convex surface facing the object side in the vicinity of the paraxial axis, and has, for example, a biconvex shape. The image side surface of the third moving lens G3 has, for example, a shape having a curvature with a sign different from that of the vicinity of the paraxial as it goes to the periphery, that is, a convex shape near the paraxial and a concave shape as it goes to the periphery. Preferably it is. The third moving lens G3 is a lens made of glass or synthetic resin. The fourth moving lens G4 is a biconcave spherical lens having negative refractive power.

  The rear fixed group 13 includes only one rear fixed lens G5. The rear fixed lens G5 has a positive refractive power and has a biconvex shape. The rear fixed lens G5 may be formed of an aspheric lens. The rear fixed lens G5 is a lens made of glass or synthetic resin. When the rear fixed lens G5 is an aspheric lens, it is preferably made of synthetic resin.

This zoom lens is configured to satisfy the following conditional expressions (1) and (2). Where fw is the focal length of the entire system at the wide-angle end, Tw is the conjugate distance (full length) at the wide-angle end, and f2g is the focal length of the second moving group 12.
4.0 <Tw / fw <6.0 (1)
1.1 <f2g / fw <1.5 (2)

With respect to these conditional expressions (1) and (2), the following numerical ranges are further preferable.
4.0 <Tw / fw <5.0 (1A)
1.1 <f2g / fw <1.4 (2A)

It is preferable that the zoom lens is further configured to satisfy the following conditional expression regarding the Abbe number of the lens in the second moving group 12. Here, f3 is the focal length of the third moving lens G3, f4 is the focal length of the fourth moving lens G4, ν3 is the Abbe number of the third moving lens G3, and ν4 is the Abbe number of the fourth moving lens G4.
| F3 / ν3 + f4 / ν4 | / fw <0.05 (3A)
In this case, it is preferable that the following conditional expression is satisfied. Here, f5 represents the focal length of the rear fixed lens G5, and ν5 represents the Abbe number of the rear fixed lens G5.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.08 (5A)
Regarding conditional expression (3A), it is more preferable that the numerical value range is as follows.
| F3 / ν3 + f4 / ν4 | / fw <0.03

This zoom lens is also preferably configured to satisfy the following conditional expression with respect to the center thickness DG4 of the fourth moving lens G4.
0.45 <DG4 / fw <0.7 (4A)

In this zoom lens, when the rear fixed lens G5 is a glass lens, it is preferably configured to satisfy the following conditional expression. Here, NG5 indicates the refractive index of the rear fixed lens G5.
NG5> 1.70 (6)
In this case, it is preferable that the following conditional expression is satisfied. Here, ν3 represents the Abbe number of the third moving lens G3, and ν4 represents the Abbe number of the fourth moving lens G4.
ν3−ν4> 20 (7)

  Next, operations and effects of the zoom lens configured as described above will be described.

  In this zoom lens, zooming is performed by moving the first moving group 11 and the second moving group 12 on the optical axis. Focus adjustment may be performed by the rear fixed group 13, but fixing the rear fixed group 13 during zooming and focus adjustment is advantageous in terms of reducing the number of moving groups, and mechanically. It is preferable because it is advantageous in terms of strength and fastness. Further, it is preferable to move both the first movement group 11 and the second movement group 12 as the focus group because the movement amount of each group can be reduced. In particular, in this zoom lens, the power of the first moving group 11 and the power of the second moving group 12 are relatively stronger than the power of the rear fixed group 13, so the rear fixed group 13 is moved. Compared to the case, the amount of movement during zooming and focusing can be reduced.

  In this zoom lens, the effective diameter of the first moving group 11 is made smaller by arranging the aperture stop St relatively on the front side, that is, on the front side of the third moving lens G3 than on the rear side. In addition, the entire lens is reduced in size.

  In this zoom lens, the cost is reduced by using a lens made of synthetic resin. Synthetic resin lenses have a greater change in optical properties due to temperature than glass lenses. In particular, focus shift and image plane fluctuation due to temperature changes are problematic. Therefore, in this zoom lens, when the negative first moving lens G1 is made of a synthetic resin lens, it is combined with the positive rear fixed lens G5 rather than only one lens made of a synthetic resin. It is preferable that the positive and negative lenses are made of synthetic resin because temperature compensation is performed and the amount of focus movement can be reduced. By the way, in the case of a small photographic lens, recently, it has become possible to independently and freely control a plurality of moving groups by a small actuator using a piezo element as a moving mechanism. Therefore, even if there is a change in the optical characteristics due to temperature, for example, it is relatively easy to control the movement of the first moving group 11 and the second moving group 12 so as to correct the change, and it is made of synthetic resin. Even if you use a lot of lenses, it doesn't matter much.

  In this zoom lens, the cost is reduced and the size is reduced by using a relatively small number of lenses in a three-group five-element configuration. In addition, by using many aspheric lenses, the overall length is shortened while correcting aberrations well. In addition to these, by satisfying each conditional expression and making appropriate power distribution and the like, the overall length is shorter and compact than the zoom lens described in Patent Document 1 (Japanese Patent Laid-Open No. 2003-270533). Therefore, a high-performance zoom optical system corresponding to the increase in the number of pixels can be obtained.

  Conditional expression (1) relates to the total length of the lens system. If the lower limit of conditional expression (1) is exceeded and the total length is made too short, it will be difficult to maintain the performance particularly at the telephoto end. If the upper limit of conditional expression (1) is exceeded, the performance is improved, but the overall length becomes too long and the market competitiveness when actually commercialized is lost. Therefore, it is more preferable to satisfy conditional expression (1A).

  Conditional expression (2) relates to the power of the second movement group 12 which is the rear movement group of the two zoom movement groups. It is preferable to satisfy the conditional expression (2) and relatively increase the power of the second moving group 12 because the total length can be easily shortened. In this case, the total length can be further shortened by satisfying conditional expression (2A), which is more preferable.

  Conditional expression (3A) relates to the achromatic condition of the positive third moving lens G3 and the negative fourth moving lens G4 in the second moving group 12. By selecting an appropriate glass material so as to satisfy the conditional expression (3A), good achromaticity can be performed inside the second moving group 12.

  Conditional expression (4A) defines an appropriate range of the center thickness of the fourth moving lens G4. By setting the center thickness to an appropriate value so as to satisfy the conditional expression (4A), it is possible to reduce fluctuations in the image plane during zooming, and in particular, it is possible to maintain a favorable image plane position in the intermediate range. It is also advantageous for reducing the axial chromatic aberration. If the center thickness becomes too thin beyond the lower limit of conditional expression (4A), the front principal point position of the entire second group 12 including the fourth lens G4 moves backward, particularly in the first group during long focus. Since the space | interval between 11 and the 2nd group 12 will not be enough, it is not preferable.

  Conditional expression (5A) relates to the condition of the Abbe number of each lens in the second moving group 12 and the rear fixed group 13. By selecting an appropriate glass material so as to satisfy this condition, it is possible to satisfy good performance equivalent to that when a cemented lens is used with respect to chromatic aberration. Furthermore, it is advantageous for reducing the overall length.

  Conditional expression (6) defines a preferable condition for the refractive index of the rear fixed lens G5, particularly when the rear fixed lens G5 is a glass lens. By satisfying conditional expression (6) and increasing the refractive index, the center thickness can be reduced, so that the overall length can be reduced. As described above, in this zoom lens, it is preferable that the first moving lens G1 and the rear fixed lens G5 are made of synthetic resin because the temperature is compensated and the amount of focus movement can be reduced. When the rear fixed lens G5 is made of a glass lens, the temperature compensation effect cannot be obtained. However, when the usage conditions are limited to a relatively narrow range of 0 ° C. to 40 ° C., for example, glass It is effective to use a lens made of steel.

  Conditional expression (7) relates to the achromatic condition of the positive third moving lens G3 and the negative fourth moving lens G4 in the second moving group 12. By selecting an appropriate glass material so as to satisfy the conditional expression (7), good achromaticity can be performed inside the second moving group 12.

  As described above, according to the zoom lens according to the present embodiment, it is possible to effectively use a synthetic resin lens to cope with an increase in the number of pixels and is particularly suitable for mounting on a small information terminal device. A compact zoom optical system can be realized at low cost.

  Next, a lens barrel suitable for housing the zoom lens according to the present embodiment will be described.

  FIG. 3 shows a cross section of the main part of the lens barrel. The lens barrel includes a lens frame 30 that forms an outer frame, and a first lens frame 41 that holds the first moving group 11 and a second lens that holds the second moving group 12 in the lens frame 30. It has a frame 42 and a third lens frame 43 that holds the rear fixed group 13. A stray light prevention stopper 44 is provided on the rearmost side of the second movement group 12 which is the final movement group.

  A guide bar 33 is also provided in the lens frame 30. The first lens frame 41 and the second lens frame 42 are held by the guide bar 33 so as to be slidable in the direction of the optical axis Z1. Thereby, the 1st movement group 11 and the 2nd movement group 12 can move to the optical axis Z1 direction.

  The lens frame 30 has a front lens frame 31 and a rear lens frame 32. The front lens frame 31 is configured using a material having a larger linear expansion coefficient than the material of the rear lens frame 32. The rear lens frame 32 is made of a material having a small coefficient of linear expansion and a small change in shape due to temperature.

  The reason why the lens frame 30 is made of two materials having different linear expansion coefficients is as follows. In general, a lens frame in the vicinity of the image sensor is made of a material having a small linear expansion coefficient and a small shape change due to temperature. On the other hand, in this zoom lens, when the moving group (first moving group 11) closer to the object side than the aperture stop St is used as the focus moving group, the focus movement amount on the telephoto side becomes the largest at high temperatures. At this time, if a material having a large linear expansion coefficient is used for the lens frame portion in front of the vicinity of the focus moving group, the lens frame 30 expands and the entire length of the lens frame 30 extends to the front side. The amount of movement of the focus movement group can be ensured by the extension of the lens frame 30. Therefore, the use of a material having a large linear expansion coefficient for the front lens barrel 31 is advantageous in focusing movement on the telephoto side at high temperatures.

  As shown in FIG. 5, the stray light prevention stopper 44 is particularly effective when the entire shape of the lens frame 30 is rectangular (XY cross section is rectangular). As shown in FIG. 4, the stray light prevention stopper 44 has, for example, a substantially rectangular opening 44B corresponding to the shape of the image sensor, and both ends of the substantially rectangular opening 44B in the short direction (Y direction). A light shielding part 44A is provided in the part. The light shielding portion 44A is provided to shield a part of the effective light beam in the short direction. The outer shape of the light shielding portion 44A is not limited to the illustrated arc shape, and may be, for example, a rectangular shape or a triangular shape.

  The operation of the stray light prevention stopper 44 will be described with reference to FIG. For example, when the entire shape of the lens frame 30 is rectangular, the light beam 52 reflected by the inner wall surface 30A tends to be stray light, particularly in the short direction of the XY cross section. Further, the light beam 51 reflected by the guide bar 33 may become stray light. The stray light prevention stopper 44 blocks these light beams 51 and 52 by the light blocking portion 44A to prevent stray light. Although the effective light beam is also shielded by providing the light shielding portion 44A, only a part of the effective light beam is shielded and hardly affects the image quality.

  The stray light prevention stopper 44 may be fixed, or may have a configuration in which the size of the opening 44B can be varied, for example. In the above description, a part of the effective light beam is shielded. However, only stray light outside the effective light beam may be shielded. It is desirable to block a part of the effective light beam only when the influence of stray light is large.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Below, only a different part from 1st Embodiment is demonstrated.

  FIG. 2 shows a configuration example of the zoom lens according to the present embodiment. This configuration example corresponds to the lens configuration of a second numerical example (FIGS. 11A and 11B) described later. FIG. 2 shows the lens arrangement at the wide angle end.

  In this zoom lens, the front-side fixed group 10 is disposed closest to the object side, and the zoom lens has a configuration that is easier to widen than the zoom lens of FIG. The front fixed group 10 is composed of only one negative meniscus lens (front fixed lens G0) having a convex surface facing the object side, for example.

This zoom lens preferably has the following numerical range with respect to conditional expression (2). This is advantageous in that the overall length is shortened.
1.1 <f2g / fw <1.45 (2B)

It is preferable that the zoom lens is further configured to satisfy the following conditional expression regarding the Abbe number of the lens in the second moving group 12. Here, f3 is the focal length of the third moving lens G3, f4 is the focal length of the fourth moving lens G4, ν3 is the Abbe number of the third moving lens G3, and ν4 is the Abbe number of the fourth moving lens G4.
| F3 / ν3 + f4 / ν4 | / fw <0.04 (3B)
In this case, it is preferable that the following conditional expression is satisfied. Here, f5 represents the focal length of the rear fixed lens G5, and ν5 represents the Abbe number of the rear fixed lens G5.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.05 (5B)
Further, regarding conditional expression (3B), it is more preferable that the following numerical range be satisfied.
| F3 / ν3 + f4 / ν4 | / fw <0.03

This zoom lens is also preferably configured to satisfy the following conditional expression with respect to the center thickness DG4 of the fourth moving lens G4.
0.5 <DG4 / fw <0.75 (4B)

  The actions and effects obtained by the conditional expressions (2B), (3B), (4B), and (5B) are the actions obtained by the conditional expressions (2A), (3A), (4A), and (5A), respectively. It is the same as the effect.

  In this zoom lens, as a three-group six-lens configuration, for example, by increasing the number of lenses as compared with the zoom lens having the five-lens configuration described in Patent Document 1, a brighter performance can be obtained, and aberrations can be improved. It has been corrected. In particular, since the front fixed group 10 is arranged closest to the object side, it becomes easier to widen the angle than when the front fixed group 10 is not arranged. Furthermore, by appropriately adopting the above-described preferable conditions as necessary, it is further advantageous for correction of aberrations, and a high-performance zoom optical system corresponding to an increase in the number of pixels can be obtained.

  As described above, according to the zoom lens according to the present embodiment, it is possible to realize a low-cost and compact optical system that is suitable for mounting on a small information terminal device, while corresponding to an increase in the number of pixels.

  Next, specific numerical examples of the zoom lens according to the present embodiment will be described.

[Examples 1-1 to 1-4]
First, four numerical examples corresponding to the first embodiment will be described. In the following, four numerical examples will be described together. FIGS. 7A and 7B are first numerical examples (Example 1-1) corresponding to the first embodiment, and specifically correspond to the cross-sectional configuration of the zoom lens shown in FIG. Lens data is shown. 8A and 8B show the second numerical example (Example 1-2), FIGS. 9A and 9B show the third numerical example (Example 1-3), FIG. 10 (A) and (B) are the fourth numerical example (Example 1-4). The cross-sectional configuration of the zoom lens according to Examples 1-2 to 1-4 is similar to that of FIG. 7A, FIG. 8A, FIG. 9A, and FIG. 10A show basic data portions of the lens data of the embodiment, and FIG. FIG. 8B, FIG. 9B, and FIG. 10B show a data portion related to the aspheric shape in the lens data of the example.

  In the column of the surface number Si in each lens data of FIGS. 7A, 8A, 9A, and 10A, the aperture St and the cover glass GC are shown for the zoom lens of each example. The number of the i-th surface (i = 1 to 13) is indicated by adding a number so that the surface of the component on the most object side including the first is first and increases sequentially toward the image side. In the column of the curvature radius Ri, the value of the curvature radius of the i-th surface from the object side is shown in correspondence with the reference symbol Ri in FIG. Also in the column of the surface interval Di, the interval on the optical axis between the i-th surface Si and the i + 1-th surface Si + 1 from the object side is shown in correspondence with the reference numerals in FIG. The unit of the value of the curvature radius Ri and the surface interval Di is millimeter (mm). In the columns of Ndj and νdj, the refractive index for the d-line (587.6 nm) and the Abbe number of the j-th (j = 1 to 6) optical element from the object side including the cover glass GC are shown.

  In the zoom lenses according to Examples 1-1 to 1-4, the first movement group 11 and the second movement group 12 move on the optical axis with zooming. , D9 are variable. In each lens data of FIG. 7A, FIG. 8A, FIG. 9A, and FIG. 10A, the maximum value and the minimum value are described as the values of these variable surface distances D4 and D9.

  As shown in FIG. 7A, in the zoom lens according to Example 1-1, the first moving lens G1 is a lens made of synthetic resin. In the zoom lens according to Example 1-2 as well, the first moving lens G1 is a synthetic resin lens as shown in FIG. In the zoom lens according to Example 1-3, as illustrated in FIG. 9A, the first moving lens G1 and the third moving lens G3 are lenses made of synthetic resin. In the zoom lens according to Example 1-4, as illustrated in FIG. 10A, the first moving lens G1, the third moving lens G3, and the rear fixed lens G5 are lenses made of synthetic resin. .

  In each lens data of FIG. 7 (A), FIG. 8 (A), FIG. 9 (A) and FIG. 10 (A), the symbol “*” attached to the left side of the surface number indicates that the lens surface is aspherical. Indicates that In the zoom lenses of Examples 1-1 to 1-3, both surfaces S1, S2 of the first moving lens G1 and both surfaces S6, S7 of the third moving lens G3 are aspherical. In the zoom lens according to Embodiment 1-4, both surfaces S10 and S11 of the rear fixed lens G5 are also aspherical. The basic lens data in FIGS. 7A, 8A, 9A, and 10A includes the curvature near the optical axis (near the paraxial axis) as the radius of curvature of these aspheric surfaces. The numerical value of the radius is shown.

In the numerical values of the aspheric data shown in FIGS. 7B, 8B, 9B, and 10B, the symbol “E” indicates that the next numerical value is 10 based. The numerical value represented by the exponential function with base 10 is multiplied by the numerical value before “E”. For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

In the aspherical surface data, the values of the coefficients A _i and KA in the aspherical surface expression expressed by the following expression (A) are described. More specifically, Z is the length (mm) of a perpendicular line drawn from a point on the aspheric surface at a height h from the optical axis to the tangential plane (plane perpendicular to the optical axis) of the apex of the aspheric surface. Show.

Z = C · h ² / {1+ (1−KA · C ² · h ² ) ^1/2 } + ΣA _i · h ⁱ (A)
However,
Z: Depth of aspheric surface (mm)
h: Distance from the optical axis to the lens surface (height) (mm)
KA: eccentricity C: paraxial curvature = 1 / R
(R: paraxial radius of curvature)
A _i : i-th (i = 3 to 10) aspheric coefficient

In the zoom lenses according to Examples 1-1 to 1-3, both surfaces S1 and S2 of the first moving lens G1 effectively use not only even-order terms but also odd-order terms as aspheric coefficients A _i. Configured. Moreover, both surfaces S6 and S7 of the third moving lens G3 are configured by effectively using only even-order terms. In the zoom lens according to Example 1-4, both surfaces S1 and S2 of the first moving lens G1 are configured to effectively use not only even-order terms but also odd-order terms as aspheric coefficients A _i. Yes. Further, both surfaces S6 and S7 of the third moving lens G3 and both surfaces S10 and S11 of the rear fixed lens G5 are configured by effectively using only even-order terms.

[Examples 2-1 and 2-2]
Next, two numerical examples corresponding to the second embodiment will be described. In the following, two numerical examples will be described together. FIGS. 11A and 11B are first numerical examples (Example 2-1) corresponding to the second embodiment, and concrete examples corresponding to the cross-sectional configuration of the zoom lens shown in FIG. Lens data is shown. FIGS. 12A and 12B are a second numerical example (Example 2-2) corresponding to the second embodiment. The sectional configuration of the zoom lens according to Example 2-2 is similar to that of FIG. 11A and 12A show basic data portions of the lens data of the embodiment, and FIGS. 12B and 12B show the embodiment. The data part regarding aspherical shape is shown among lens data. The meanings of the numerical values shown in each lens data are the same as those in Examples 1-1 to 1-4.

  As shown in FIG. 11A, in the zoom lens according to Example 2-1, the first moving lens G1 is a lens made of synthetic resin. As shown in FIG. 12A, in the zoom lens according to Example 2-2, the first moving lens G1 and the rear fixed lens G5 are lenses made of synthetic resin.

In the zoom lenses according to Examples 2-1 and 2-2, both surfaces S3 and S4 of the first moving lens G1 and both surfaces S8 and S9 of the third moving lens G3 are aspherical. In both the zoom lenses according to Examples 2-1 and 2-2, both surfaces S3 and S4 of the first moving lens G1 effectively use not only even-order terms but also odd-order terms as aspheric coefficients A _i. It is configured using. Both surfaces S8 and S9 of the third moving lens G3 are configured by effectively using only even-order terms.

  FIG. 13 collectively shows values relating to the above-described conditional expressions for the respective examples. As shown in FIG. 13, the zoom lens according to each example satisfies the conditional expressions (1) and (2).

  In particular, the zoom lenses according to Examples 1-1 to 1-4 satisfy the numerical ranges of the conditional expressions (1A), (2A), (3A), (4A), and (5A). Further, the zoom lenses according to Examples 1-2 and 1-3 satisfy the numerical ranges of the conditional expressions (6) and (7) at the same time.

  In particular, the zoom lenses according to Examples 2-1 and 2-2 satisfy the numerical ranges of the conditional expressions (1B), (2B), (3B), (4B), and (5B). Furthermore, the zoom lens according to Example 2-1 satisfies the numerical ranges of conditional expressions (6) and (7) at the same time.

  FIGS. 14A to 14C show spherical aberration, astigmatism, and distortion (distortion aberration) at the wide-angle end in the zoom lens of Example 1-1. FIGS. 15A to 15C show similar aberrations at the telephoto end. Each aberration diagram shows an aberration with a wavelength of 540 nm as a reference wavelength, while the spherical aberration diagram and the astigmatism diagram also show aberrations for wavelengths of 420 nm and 680 nm. In the astigmatism diagram, the solid line indicates the sagittal direction and the broken line indicates the tangential direction. FNO. Indicates an F value, and ω indicates a half angle of view.

  Similarly, various aberrations of the zoom lens of Example 1-2 are shown in FIGS. 16A to 16C (wide-angle end) and FIGS. 17A to 17C (telephoto end). Similarly, various aberrations of the zoom lens of Example 1-3 are shown in FIGS. 18A to 18C (wide-angle end) and FIGS. 19A to 19C (telephoto end). Similarly, various aberrations of the zoom lens of Example 1-4 are shown in FIGS. 20A to 20C (wide-angle end) and FIGS. 21A to 21C (telephoto end).

  Similarly, various aberrations of the zoom lens of Example 2-1 are shown in FIGS. 22A to 22C (wide-angle end) and FIGS. 23A to 23C (telephoto end). Similarly, various aberrations of the zoom lens of Example 2-2 are shown in FIGS. 24A to 24C (wide-angle end) and FIGS. 25A to 25C (telephoto end).

  As can be seen from the numerical data and aberration diagrams, a compact and high-performance zoom optical system suitable for mounting on a small information terminal device can be realized in each embodiment.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made. For example, the radius of curvature, the surface interval, and the refractive index of each lens component are not limited to the values shown in the above numerical examples, and may take other values.

1 is a lens cross-sectional view illustrating a configuration example of a zoom lens according to a first embodiment of the present invention and corresponding to Example 1-1. 1 is a lens cross-sectional view illustrating a configuration example of a zoom lens according to a second embodiment of the present invention and corresponding to Example 2-1. It is sectional drawing which shows the principal part structure of the lens barrel applied to the zoom lens which concerns on the 1st Embodiment of this invention. It is a front view which shows the structural example of the stray light prevention stopper used for the zoom lens which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the shape of the lens barrel suitable for using the stray light prevention stopper in the 1st Embodiment of this invention. It is explanatory drawing which shows the effect | action of a stray light prevention stopper. FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 1-1. FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 1-2. FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 1-3. FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 1-4. FIG. 6 is a diagram illustrating lens data of a zoom lens according to Example 2-1. It is a figure which shows the lens data of the zoom lens which concerns on Example 2-2. It is a figure which shows the value regarding the conditional expression which the zoom lens concerning each Example satisfy | fills. FIG. 7 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1-1. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Example 1-1. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1-2. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Example 1-2. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1-3. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at a telephoto end of a zoom lens according to Example 1-3. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1-4. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at a telephoto end of a zoom lens according to Example 1-4. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide angle end of the zoom lens according to Example 2-1. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Example 2-1. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 2-2. FIG. 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion at a telephoto end of a zoom lens according to Example 2-2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Front side fixed group, 11 ... 1st movement group, 12 ... 2nd movement group, 13 ... Rear side fixed group, GC ... Cover glass, G0 ... Front side fixed lens, G1 ... 1st movement lens, G2 ... 2nd movement Lens, G3: Third moving lens, G4: Fourth moving lens, G5: Rear fixed lens, Ri: Curvature radius of i-th lens surface from object side, Di: i-th and i + 1-th from object side Surface distance from the lens surface, Simg ... imaging surface (imaging surface), Z1 ... optical axis.

Claims (20)

At least one fixed group that is fixed during zooming, and first and second moving groups that move on the optical axis during zooming and have a relatively strong refractive power with respect to the fixed group,
The first moving group has a negative refractive power as a whole,
The second moving group as a whole has a positive refractive power, and in order from the object side, has an aspherical surface and has a positive refractive power lens having a convex surface facing the object side in the vicinity of the paraxial axis, and negative refraction. It consists of a biconcave lens with power,
At least one of the first and second moving groups has a lens made of synthetic resin,
A zoom lens having a synthetic resin lens, characterized in that the following conditional expression is satisfied.
4.0 <Tw / fw <6.0 (1)
1.1 <f2g / fw <1.5 (2)
However,
fw: focal length of the entire system at the wide angle end Tw: conjugate distance (full length) at the wide angle end
f2g: focal length of the second moving group 2. The zoom lens having a synthetic resin lens according to claim 1, wherein at least one of the first and second moving groups also serves as a focus adjusting moving group. 3. A rear fixed group that is fixed at the most image side during zooming, and a first and second moving group that moves on the optical axis during zooming and has a relatively strong refractive power with respect to the rear fixed group. And consist of
The first moving group has a negative refractive power as a whole, and in order from the object side, a first moving lens having a negative refractive power having an aspheric surface and a second moving lens having a positive refractive power. Configured,
The second moving group has a positive refractive power as a whole, and in order from the object side, a third moving lens having a positive refractive power having an aspherical surface and a convex surface facing the object side in the vicinity of the paraxial axis; A bi-concave fourth moving lens having negative refractive power,
The rear fixed group is composed of only one biconvex lens having a positive refractive power,
At least one of the first and second moving groups has a lens made of synthetic resin,
A zoom lens having a synthetic resin lens, characterized in that the following conditional expression is satisfied.
4.0 <Tw / fw <5.0 (1A)
1.1 <f2g / fw <1.4 (2A)
However,
fw: focal length of the entire system at the wide angle end Tw: conjugate distance (full length) at the wide angle end
f2g: focal length of the second moving group The zoom lens having a synthetic resin lens according to claim 3, wherein at least one of the first and second moving groups also serves as a focus adjusting moving group. 5. The zoom lens having a synthetic resin lens according to claim 3, wherein the following conditional expression is satisfied with respect to the Abbe number of the lens in the second moving group. .
| F3 / ν3 + f4 / ν4 | / fw <0.05 (3A)
However,
f3: focal length of the third moving lens f4: focal length of the fourth moving lens ν3: Abbe number of the third moving lens ν4: Abbe number of the fourth moving lens The synthetic resin lens according to any one of claims 3 to 5, further comprising: a center thickness DG4 of the fourth moving lens so as to satisfy the following conditional expression: Zoom lens.
0.45 <DG4 / fw <0.7 (4A) The synthetic resin lens according to claim 5, wherein the lens is configured to satisfy the following conditional expression with respect to the Abbe number of the lenses in the second moving group and the rear fixed group. A zoom lens.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.08 (5A)
However,
f5: Focal length of lens constituting rear fixed group ν5: Abbe number of lens constituting rear fixed group The lens constituting the rear fixed group is a glass lens,
The zoom lens having a synthetic resin lens according to any one of claims 3 to 7, wherein the zoom lens is configured to satisfy the following conditional expression.
NG5> 1.70 (6)
However,
NG5: Refractive index of the lens constituting the rear fixed group The zoom lens having a synthetic resin lens according to claim 8, wherein the following conditional expression is satisfied with respect to the Abbe number of the lens in the second moving group.
ν3−ν4> 20 (7)
However,
ν3: Abbe number of the third moving lens ν4: Abbe number of the fourth moving lens 8. The synthetic resin lens according to claim 3, wherein the first moving lens is a lens made of a synthetic resin, and the third moving lens is a lens made of glass. 9. Zoom lens. The synthetic resin lens according to any one of claims 3 to 7, wherein both the first moving lens and the lens constituting the rear fixed group are synthetic resin lenses. Zoom lens. A front fixed group that is fixed at the most object side when zoomed, a rear fixed group that is fixed and positioned at the most image side when zooming, and moves on the optical axis during zooming, and the front fixed group and the rear side A first moving group and a second moving group having a relatively strong refractive power with respect to the fixed group;
The front fixed group is composed of only one meniscus lens,
The first moving group has a negative refractive power as a whole, and in order from the object side, a first moving lens having a negative refractive power having an aspheric surface and a second moving lens having a positive refractive power. Configured,
The second moving group has a positive refractive power as a whole, and in order from the object side, a third moving lens having a positive refractive power having an aspherical surface and a convex surface facing the object side in the vicinity of the paraxial axis; A bi-concave fourth moving lens having negative refractive power,
The rear fixed group is composed of only one biconvex lens having a positive refractive power,
At least the first moving group has a lens made of synthetic resin,
A zoom lens having a synthetic resin lens, characterized in that the following conditional expression is satisfied.
4.0 <Tw / fw <6.0 (1)
1.1 <f2g / fw <1.45 (2B)
However,
fw: focal length of the entire system at the wide angle end Tw: conjugate distance (full length) at the wide angle end
f2g: focal length of the second moving group The zoom lens having a synthetic resin lens according to claim 12, wherein at least one of the first and second moving groups also serves as a focus adjusting moving group. The zoom lens having a synthetic resin lens according to claim 12 or 13, further configured to satisfy the following conditional expression.
| F3 / ν3 + f4 / ν4 | / fw <0.04 (3B)
However,
f3: focal length of the third moving lens f4: focal length of the fourth moving lens ν3: Abbe number of the third moving lens ν4: Abbe number of the fourth moving lens Furthermore, regarding the center thickness DG4 of the fourth moving lens, the following conditional expression is satisfied: The synthetic resin lens according to any one of claims 12 to 14, Zoom lens.
0.5 <DG4 / fw <0.75 (4B) Furthermore, it is comprised so that the following conditional expressions may be satisfied regarding the Abbe number of the lens in the said 2nd movement group and the said back side fixed group. The synthetic resin lens of Claim 14 characterized by the above-mentioned. A zoom lens.
| F3 / ν3 + f4 / ν4 + f5 / ν5 | / fw <0.05 (5B)
However,
f5: Focal length of lens constituting rear fixed group ν5: Abbe number of lens constituting rear fixed group The lens constituting the rear fixed group is a glass lens,
The zoom lens having a synthetic resin lens according to any one of claims 12 to 16, wherein the zoom lens is configured to satisfy the following conditional expression.
NG5> 1.70 (6)
However,
NG5: Refractive index of the lens constituting the rear fixed group The zoom lens having a synthetic resin lens according to claim 17, wherein the following conditional expression is satisfied with respect to the Abbe number of the lens in the second moving group.
ν3−ν4> 20 (7)
However,
ν3: Abbe number of the third moving lens ν4: Abbe number of the fourth moving lens 17. The synthetic resin lens according to claim 12, wherein the first moving lens is a lens made of a synthetic resin, and the third moving lens is a glass lens. Zoom lens. The synthetic resin lens according to any one of claims 12 to 16, wherein both the first moving lens and the lens constituting the rear fixed group are synthetic resin lenses. Zoom lens.

Images