JP5050700B2 - Variable magnification optical system, imaging device, and digital device - Google Patents

Description

  The present invention relates to a variable magnification optical system suitably used for a video camera, an electronic still camera, and the like, and more particularly, to a variable magnification optical system that can be reduced in size, an image pickup apparatus including the same, and a digital apparatus equipped with the image pickup apparatus. .

  In recent years, mobile terminals equipped with portable communication functions such as mobile phones and PDAs (Personal Digital Assistants) have been remarkably widespread, and these devices have built-in imaging devices capable of taking compact still images and moving images. Many. In general, image pickup apparatuses mounted on these devices are severely limited in size (size) and cost. For this reason, as compared with a digital camera, an imaging apparatus including a single focus optical system composed of about 2 to 4 plastic lenses using a small pixel and a small imaging element is generally employed. However, the image pickup devices mounted on these devices have also been increased in pixel count and functionality, so that they can be used for high pixel image sensors and can also shoot subjects away from the photographer. Therefore, there is a demand for a compact variable power optical system that can be mounted on these devices.

Examples of the variable power optical system of the image pickup apparatus mounted on these devices include Patent Document 1 and Patent Document 2. The variable magnification optical system disclosed in Patent Document 1 is characterized by three negative and positive three components and a very small number of lenses. In addition, the variable magnification optical system disclosed in Patent Document 2 has four negative, positive, and positive four components, and the first lens group is fixed to reduce the size.
JP 2005-037935 A JP 2006-227129 A

  By the way, the variable power optical system disclosed in Patent Document 1 has insufficient correction of axial chromatic aberration and lateral chromatic aberration to meet the above requirements, and it is difficult to sufficiently cope with the recent increase in the number of pixels. In the variable power optical system disclosed in Patent Document 2, the second and third lens groups are each composed of a single lens, so that correction of spherical aberration and astigmatism is insufficient for the above requirement. It is.

  As described above, these variable magnification optical systems are compact, but their aberration correction is insufficient, so that it is difficult to sufficiently cope with a high-pixel image sensor.

  The present invention has been made in view of the above-described circumstances, and its object is to provide a variable that can correct various aberrations of spherical aberration, chromatic aberration, and astigmatism as compared with the background art while being compact. To provide a double optical system, an image pickup apparatus including the same, and a digital apparatus.

In order to solve the above technical problem, the present invention provides a variable magnification optical system, an imaging device, and a digital device having the following configurations. Note that the terms used in the following description are defined as follows in this specification.
(A) A refractive index is a refractive index with respect to the wavelength (587.56 nm) of d line | wire.
(B) Abbe number is determined when the refractive index for d line, F line (486.13 nm) and C line (656.28 nm) is nd, nF, nC and Abbe number is νd, respectively.
νd = (nd−1) / (nF−nC)
The Abbe number νd obtained by the definition formula
(C) The notation regarding the surface shape is a notation based on the paraxial curvature.
(D) When the notation "concave", "convex" or "meniscus" is used for the lens, these represent the lens shape in the vicinity of the optical axis (near the center of the lens) (based on the paraxial curvature) Notation).
(E) The notation of optical power in each single lens constituting the cemented lens is power when both sides of the lens surface of the single lens are air.
(F) Since the resin material used for the composite aspherical lens has only an additional function of the substrate glass material, it is not treated as a single optical member, but is treated as if the substrate glass material has an aspherical surface, and the number of lenses Shall be handled as one sheet. The lens refractive index is also the refractive index of the glass material serving as the substrate. The composite aspherical lens is a lens that is aspherical by applying a thin resin material on a glass material to be a substrate.

A variable magnification optical system according to an aspect of the present invention includes, in order from the object side to the image side, a first lens group having a negative optical power, a second lens group having a positive optical power, and a negative optical The first lens group and the second lens group move so as to narrow each other's distance in zooming from the wide-angle end to the telephoto end. The lens group is composed of one negative lens, and the second lens group is composed of at least one positive lens and at least one negative lens, and the following condition (1) It is characterized by satisfying the formula.
| Hg2 | / Rg2> 0.15 (1)
However, Hg2 is the principal ray height (distance from the optical axis) of the light beam corresponding to the maximum image height at the most object side lens surface of the second lens group at the wide angle end, and Rg2 is This is the maximum effective radius of the lens surface closest to the object side of the two lens groups.

  In this configuration, the zoom lens having a zoom ratio of about 2 to 3 times is a negative lead optical system that is advantageous in terms of the overall optical length, the front lens diameter, and error sensitivity. By adopting a configuration including negative and positive, it is possible to satisfactorily correct spherical aberration, chromatic aberration, and astigmatism while maintaining compactness of the variable magnification optical system by shortening the variable magnification movement amount. For example, the zoom lens system can be made compact by configuring the first lens group with a single lens. By configuring the second lens group with one positive and one negative lens, it is possible to sufficiently correct axial chromatic aberration and spherical aberration. By satisfying conditional expression (1), off-axis aberrations remaining in the first lens group can be corrected by the most object side lens in the second lens group.

Further, in another aspect, in the above-described variable magnification optical system, further characterized in including that an aperture stop is disposed on the image side of the most object side lens surface of the second lens group.

  In this configuration, the zoom lens having a zoom ratio of about 2 to 3 times is a negative lead optical system that is advantageous in terms of the overall optical length, the front lens diameter, and error sensitivity. By adopting a configuration including negative and positive, it is possible to satisfactorily correct spherical aberration, chromatic aberration, and astigmatism while maintaining compactness of the variable magnification optical system by shortening the variable magnification movement amount. For example, the zoom lens system can be made compact by configuring the first lens group with a single lens. By configuring the second lens group with one positive and one negative lens, it is possible to sufficiently correct axial chromatic aberration and spherical aberration. By disposing the aperture stop closer to the image side than the most object side lens surface of the second lens group, off-axis aberration can be corrected by the most object side lens of the second lens group.

  In the above-described variable magnification optical system, it is preferable that the most object side lens of the second lens group has a positive optical power.

  According to this configuration, it is possible to effectively correct astigmatism and lateral chromatic aberration remaining in the first lens group by using the most object side lens of the second lens group as a positive lens.

  In the above-described variable magnification optical system, preferably, the first lens group is fixed at the variable magnification.

  According to this configuration, the effective lens diameter of the first lens group can be suppressed by fixing the first lens group. Further, when the first lens group is movable, the driving device must be disposed outside the first lens group, and the size in the outer diameter direction becomes large. According to this configuration, the outer diameter direction is small. It is very effective for conversion.

In the above-described variable magnification optical system, it is preferable that the following conditional expression (2) is satisfied at the wide angle end.
| Hg2 | / TLw> 0.01 (2)
However, TLw is the distance on the optical axis from the surface vertex of the lens surface closest to the object side to the image plane at the wide-angle end when the object distance is infinite (however, the back focus is the air equivalent length). .

  According to this configuration, by satisfying conditional expression (2), it is possible to effectively correct off-axis aberrations with the most object side lens in the second lens group.

In the above-described variable magnification optical system, it is preferable that the negative lens of the first lens group satisfies the following conditional expressions (3) and (4).
N1 <1.65 (3)
v1> 50 (4)
Here, N1 is the refractive index of the negative lens in the first lens group, and v1 is the Abbe number of the negative lens in the first lens group.

  In this configuration, if the upper limit of conditional expression (3) is exceeded, it is difficult to correct astigmatism occurring in the first lens group with other lens groups, which is not preferable. On the other hand, if the lower limit of conditional expression (4) is not reached, it is difficult to correct lateral chromatic aberration occurring in the first lens group with other lens groups, which is not preferable.

In the above-described variable magnification optical system, it is preferable that the second lens group satisfies the following conditional expression (5).
0.6 <f2 / fw <1.5 (5)
Here, f2 is the combined focal length of the second lens group, and fw is the combined focal length of the entire optical system at the wide angle end.

  In this configuration, if the upper limit of conditional expression (5) is exceeded, the optical power of the second lens group is too weak, and it is difficult to obtain a zoom ratio of about 2 to 3 times while ensuring compactness. This is not preferable. On the other hand, if the lower limit of conditional expression (5) is not reached, the decentration error sensitivity of the second lens group becomes very high, and manufacturing becomes difficult, which is not preferable.

In the above-described variable magnification optical system, it is preferable that the most image side lens of the variable magnification optical system satisfies the following conditional expressions (6) and (7).
1.5 <Ni (6)
vi <40 (7)
Here, Ni is the refractive index of the most image side lens in the variable magnification optical system, and vi is the Abbe number of the most image side lens in the variable magnification optical system.

  In this configuration, if the lower limit of conditional expression (6) is not reached, it is difficult to adjust the off-axis ray angle incident on the image plane, which is not preferable. On the other hand, if the upper limit of conditional expression (7) is exceeded, it will be difficult to sufficiently correct lateral chromatic aberration in terms of compatibility with high pixel image sensors, which is not preferable.

In the above-described variable magnification optical system, preferably, when focusing from an object at infinity to an object at a short distance, the third lens unit moves and satisfies the following conditional expression (8).
0.8 <| f3 / fw | <1.5 (8)
Here, f3 is the combined focal length of the third lens group, and fw is the combined focal length of the entire optical system at the wide angle end.

  In this configuration, if the upper limit of conditional expression (8) is exceeded, the optical power of the third lens group will be weakened, and the amount of movement of the third lens group will increase in the case of focusing, which will hinder downsizing, which is preferable. Absent. On the other hand, if the lower limit of conditional expression (8) is not reached, the decentration error sensitivity of the third lens group becomes very high, and manufacturing becomes difficult, which is not preferable.

In the above-described variable magnification optical system, it is preferable that the following conditional expression (9) is satisfied.
0.1 <Rg1 / TLw <0.3 (9)
However, Rg1 is the maximum effective radius of the most object side lens surface in the variable magnification optical system, and TLw is from the surface vertex to the image surface of the most object side lens surface at the wide angle end when the object distance is infinite. The distance on the optical axis (where the back focus is the air equivalent length).

  In this configuration, if the upper limit of conditional expression (9) is exceeded, the cross-sectional area of the variable magnification optical system increases, so even if the total lens length of the variable magnification optical system is shortened, it prevents the volume reduction of the variable magnification optical system, It is not preferable. On the other hand, if the lower limit of conditional expression (9) is not reached, the optical power of the first lens group becomes too strong and the decentration error sensitivity becomes very high, which makes it difficult to manufacture and is not preferable.

In the above-described variable magnification optical system, it is preferable that the following conditional expression (10) is satisfied at the telephoto end.
T12 / (fw × ft) ^1/2 <0.2 (10)
Where T12 is the distance on the optical axis between the first lens group and the second lens group at the telephoto end, and fw is the combined focal length of the entire optical system at the wide-angle end, ft is the combined focal length of the entire optical system at the telephoto end.

  In this configuration, if the upper limit of the conditional expression (10) is exceeded, the substantial zooming movement amount of the second lens group becomes small, so that the optical power of the second lens group becomes strong and the manufacture becomes difficult, It is not preferable.

  In the above-described variable magnification optical system, it is preferable that the zoom lens system includes only the first to third lens groups.

  According to this configuration, the three-group configuration of the first to third lens groups can reduce the cost and greatly shorten the total optical length by simplifying the mechanical mechanism.

In the above-described variable magnification optical system, it is preferable that the most object side lens of the second lens group satisfies the following conditional expression (11).
−0.4 <Rfg2 / Rrg2 <−0.2 (11)
Here, Rfg2 is the radius of curvature of the object side surface of the most object side lens in the second lens group, and Rrg2 is the radius of curvature of the image side surface of the most object side lens in the second lens group.

  In general, when downsizing is performed, the optical power of each lens in the second lens group is increased in order to suppress the amount of movement of the variable power group, and as a result, the error sensitivity becomes too high and manufacturing becomes difficult. . In particular, the most object side lens has the strongest optical power in the second lens group.

  In this configuration, it is possible to suppress the manufacturing error sensitivity of the most object side lens of the second lens group by satisfying conditional expression (11).

In the above-described variable magnification optical system, preferably, the following conditional expression (12) is satisfied.
1.0 <Lb / fw <1.5 (12)
Where Lb is the back focus (air equivalent length) at the telephoto end, and fw is the combined focal length of the entire optical system at the wide angle end.

  In this configuration, if the upper limit of conditional expression (12) is exceeded, the optical power of the negative lens in the first lens group becomes too strong, and off-axis aberrations that occur in the first lens group are corrected in other lens groups. It is difficult to do so. On the other hand, if the lower limit of conditional expression (12) is not reached, the variable magnification burden of the third lens group is reduced, the total optical length is increased, and this is not preferable because it hinders downsizing.

  In the above-described variable magnification optical system, preferably, a fourth lens group having a positive optical power is further provided on the image side of the third lens group.

  According to this configuration, by disposing the fourth lens group on the image side of the third lens group, it is possible to improve the telecentricity of light incident on the imaging surface.

  In the above-described variable magnification optical system, it is preferable that the zoom lens system includes only the first to fourth lens groups.

  According to this configuration, the four-group configuration of the first to fourth lens groups makes it relatively easy to achieve both shortening of the optical total length and maintaining telecentricity.

In the variable magnification optical system further including the fourth lens group, it is preferable that the most object side lens of the second lens group satisfies the following conditional expression (13).
0.3 <Rfg2 / Rrg2 <0.6 (13)
Here, Rfg2 is the radius of curvature of the object side surface of the most object side lens in the second lens group, and Rrg2 is the radius of curvature of the image side surface of the most object side lens in the second lens group.

  As described above, in general, when downsizing is performed, the optical power of each lens in the second lens group is increased in order to suppress the movement amount of the zooming group, and as a result, the error sensitivity becomes too high. Manufacturing becomes difficult. In particular, the most object side lens has the strongest optical power in the second lens group.

  In this configuration, by satisfying conditional expression (13), it is possible to suppress the manufacturing error sensitivity of the most object side lens of the second lens group.

In the above-described variable magnification optical system, it is preferable that the following conditional expression (14) is satisfied.
0.2 <Lb / fw <0.4 (14)
Where Lb is the back focus (air equivalent length) at the telephoto end, and fw is the combined focal length of the entire optical system at the wide angle end.

  In this configuration, if the upper limit of conditional expression (14) is exceeded, the telecentricity of the off-axis light incident angle on the image plane is lost at the telephoto end, and the peripheral illumination is lowered, which is not preferable. On the other hand, if the lower limit of conditional expression (14) is not reached, the difference between the off-axis light incident angles on the image plane at the wide-angle end and the telephoto end becomes too large, and the ambient illuminance is reduced at any point.

  In the above-described variable magnification optical system, preferably, the aperture stop is disposed on the image side with respect to the most image side lens surface of the second lens group.

  According to this configuration, it is possible to correct off-axis aberrations by disposing the aperture stop closer to the image side than the most image side lens surface of the second lens group.

  In the above-described variable magnification optical system, it is preferable that there are only two movable lens groups in the variable magnification.

  By limiting the movable group to two groups, that is, a zooming group and an image plane correction group by zooming, the occupied volume of the driving device for driving these is reduced and the mechanical mechanism is simplified, so that the zooming optical system It is possible to reduce the size of the system.

  In the above-described variable magnification optical system, it is preferable that the third lens group includes at least one aspheric surface.

  According to this configuration, it is relatively easy to ensure telecentricity over the entire imaging surface by having at least one aspheric surface in the third lens group.

  In addition, the above-described variable magnification optical system preferably includes at least one lens made of a resin material.

  According to this configuration, by using a lens made of a resin material, mass production can be performed with stable quality, and costs can be reduced.

  In the above-described variable magnification optical system, it is preferable that the at least one lens made of a resin material is disposed in the third lens group or closer to the image side than the third lens group.

  According to this configuration, by arranging the lens made of the resin material in the third lens group or on the image side of the third lens group, it is possible to reduce the cost while minimizing the influence on the optical performance. It becomes possible.

  In the above-described variable magnification optical system, preferably, the second lens group is configured to move to the object side during the variable magnification from the wide-angle end to the telephoto end, and include three or less lenses. It consists of

  According to this configuration, by setting the number of lenses of the second lens group to 3 or less, it is possible to reduce the weight of the movable group and reduce the load on the driving device that drives the second lens group.

  In the above-described variable magnification optical system, it is preferable that the second lens group includes a cemented lens.

  According to this configuration, it is possible to suppress the manufacturing error sensitivity of the second lens group by using the cemented lens for the second lens group.

  In the above-described variable magnification optical system, it is preferable that the third lens group includes two or more lenses.

  According to this configuration, by configuring the third lens group with two or more lenses, it is possible to sufficiently correct the residual aberration in the first and second lens groups in terms of corresponding to the high pixel imaging device. Become.

  An imaging apparatus according to another aspect of the present invention includes the zoom optical system having any of the above-described configurations, and an image sensor that converts an optical image into an electrical signal, and the zoom optical system Is capable of forming an optical image of an object on the light receiving surface of the image sensor.

  A digital apparatus according to another aspect of the present invention includes the imaging device having the above-described configuration, and a control unit that causes the imaging device to perform at least one of shooting a still image and moving image shooting of a subject, The variable power optical system of the image pickup apparatus is assembled on the light receiving surface of the image pickup device so that an optical image of the subject can be formed. Preferably, the digital device comprises a mobile terminal.

  According to the present invention, it is possible to provide a variable magnification optical system, an imaging device, and a digital device that can correct various aberrations of spherical aberration, chromatic aberration, and astigmatism as compared with the background art while ensuring compactness. It becomes.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

<Description of configuration of variable magnification optical system>
FIG. 1 is a lens cross-sectional view schematically illustrating the configuration of the variable magnification optical system in the embodiment.

  In FIG. 1, a zoom optical system 1 forms an optical image of an object (subject) on a light receiving surface (image surface) of an image sensor 16 that converts an optical image into an electrical signal. In order from the object side to the image side, a first lens group 11 having negative optical power, a second lens group 12 having positive optical power, and a third lens group 13 having negative optical power are provided. In addition, the zoom lens system includes a zoom optical system in which the first lens group 11 and the second lens group 12 move so that the distance between the first lens group 11 and the second lens group 12 becomes narrower when zooming from the wide-angle end to the telephoto end. The variable power optical system 1 illustrated in FIG. 1 has the same configuration as the variable power optical system 1A (FIG. 4) of Example 1 described later.

  In FIG. 1, the first lens group 11 is fixed at zooming and is composed of a single biconcave negative lens 111, and the second lens group 12 moves to the object side at zooming, In order from the image side to the image side, the lens includes a biconvex positive lens 121, a biconvex positive lens 122, and a negative meniscus lens 123 convex on the image side. In this example, a negative meniscus lens 131 convex toward the object side and a negative meniscus lens 132 convex toward the object side are shown in order from the image side to the image side. Thus, in the variable magnification optical system 1, the second lens group 12 has at least one positive lens and at least one negative lens. In the example shown in FIG. 1, the positive lens 121 of the second lens group 12 and the negative meniscus lens 132 of the third lens group 13 are both aspheric. The positive lens 122 and the negative meniscus lens 123 of the second lens group 12 are cemented lenses that are fixedly integrated. The negative meniscus lens 132 in the third lens group 13 is a lens made of a resin material such as plastic.

  Note that the number of lenses in the cemented lens is not represented by one for the entire cemented lens, but by the number of single lenses constituting the cemented lens.

Then, at the wide angle end, the variable magnification optical system 1 sets the principal ray height (distance from the optical axis) of the light beam corresponding to the maximum image height at the most object side lens surface of the second lens group 12 to Hg2, and When the maximum effective radius of the most object side lens surface of the second lens group 12 is Rg2, the following conditional expression (1) is satisfied.
| Hg2 | / Rg2> 0.15 (1)

  The variable magnification optical system 1 having such a configuration is a so-called negative lead optical system having three components of “negative / positive / negative” in order from the object side. For this reason, a zoom lens having a zoom ratio of about 2 to 3 is advantageous in terms of the overall optical length, the size of the front lens diameter, and error sensitivity.

  And, by adopting a configuration including negative and positive, while maintaining compactness of the variable magnification optical system 1 by shortening the variable magnification movement amount, the variable magnification ratio covers the entire variable magnification range of about 2 to 3 times. Thus, it is possible to satisfactorily correct spherical aberration, chromatic aberration, astigmatism, and the like. That is, in the example shown in FIG. 1, the first lens group 11 is composed of a single lens 111. For this reason, downsizing of the variable magnification optical system 1 is maintained. The second lens group 12 includes at least one positive lens and at least one negative lens. For this reason, it is possible to sufficiently correct axial chromatic aberration and spherical aberration. The variable magnification optical system 1 satisfies the conditional expression (1). Therefore, the off-axis aberration remaining in the first lens group 11 can be corrected by the most object side lens of the second lens group 12.

Further, from the viewpoint of off-axis aberration and manufacturing error sensitivity, the zoom optical system 1 more preferably satisfies the following conditional expression (1 ′).
| Hg2 | / Rg2> 0.5 (1 ′)

  If the lower limit of conditional expression (1 ′) is not reached, the effect of correcting the off-axis aberration remaining in the first lens group 11 with the most object side lens in the second lens group 12 becomes weak. For this reason, in particular, the optical performance at the wide-angle end is deteriorated, or the manufacturing error sensitivity is increased when the optical performance is maintained.

  From the viewpoint of correcting off-axis aberrations, or the variable magnification optical system 1 includes, for example, an optical aperture (aperture stop) 14 disposed on the image side of the most object side lens surface of the second lens group 12. Good. As described above, the optical aperture 13 is disposed on the image side of the most object side lens surface of the second lens group 12, so that the off-axis aberration can be corrected by the most object side lens of the second lens group 12. Become.

  A filter 15 and an image sensor 16 are arranged on the image side of the variable magnification optical system 1. The filter 15 is an optical element having a parallel plate shape, and schematically represents various optical filters, a cover glass of the imaging element, and the like. An optical filter such as a low-pass filter or an infrared cut filter can be appropriately arranged depending on the usage, imaging device, camera configuration, and the like. The image sensor 16 performs photoelectric conversion into image signals of R (red), G (green), and B (blue) components in accordance with the amount of light in the optical image of the subject formed by the variable magnification optical system 1. This element outputs to a predetermined image processing circuit (not shown). As a result, an object-side optical image on the object side is guided to the light-receiving surface of the image sensor 16 at an appropriate zoom ratio along the optical axis AX by the zoom optical system 1, and the optical image of the subject is captured by the image sensor 16. Is done.

  In the variable magnification optical system 1, the most object side lens 121 of the second lens group 12 has a positive optical power. Therefore, the astigmatism and lateral chromatic aberration remaining in the first lens group 11 can be effectively corrected.

  In the variable magnification optical system 1, both surfaces of the positive lens 121 are aspheric surfaces, and the positive lens 121 of the second lens group 12 is provided with an aspheric surface. For this reason, it becomes possible to correct | amend favorably the spherical aberration and coma aberration which generate | occur | produce by the increase in the optical power of the 2nd lens group 12 accompanying compactification at the point corresponding to a high pixel image pick-up element.

  In the variable magnification optical system 1, the second lens group 12 is arranged in order of a biconvex positive lens 121 and a cemented lens of a positive lens 122 and a negative meniscus lens 123 from the object side. For this reason, it is possible to appropriately distribute the variable magnification burden of the entire second lens group 12 to each of the lenses 121 to 123, thereby reducing the manufacturing error sensitivity. Further, this arrangement makes it possible to sufficiently correct axial chromatic aberration at a point corresponding to the high pixel image sensor. From the same viewpoint, the biconvex positive lens 121 may be a positive lens convex to the object side, and the negative meniscus lens 123 may be a negative lens.

  In the variable magnification optical system 1, the negative meniscus lens 132 of the third lens group 13 has two aspheric surfaces, and the third lens group 13 includes at least one aspheric surface. For this reason, it is relatively easy to ensure telecentricity over the entire imaging surface.

  In the variable magnification optical system 1, the third lens group 13 includes two lenses. For this reason, it is possible to sufficiently correct the residual aberrations in the first and second lens groups 11 and 12 in terms of corresponding to the high pixel image pickup device. From the same viewpoint, the third lens group 13 may be configured to include two or more lenses.

  In the variable magnification optical system 1, the first lens group 11 is fixed at the variable magnification. For this reason, the effective lens diameter of the first lens group 11 can be suppressed. In the case where the first lens group 11 is movable, the driving device has to be disposed outside the first lens group 11 in the radial direction, and the size in the outer diameter direction becomes large. It is very effective.

  In the zoom optical system 1, the second and third lens groups 12 and 13 move during zooming. Since there are only two lens groups that can move in this manner in zooming, the size of the zooming optical system 1 is reduced in order to reduce the occupied volume of the driving device that drives these lenses and to simplify the mechanical mechanism. Can be miniaturized.

  In the variable magnification optical system 1, the second lens group 12 is configured to move to the object side during variable magnification and include three lenses 121 to 123. For this reason, the movable second lens group 12 is reduced in weight, and it becomes possible to reduce the load of a driving device (not shown) that drives the second lens group 12. From the same viewpoint, the second lens group 12 may be configured to include three or less lenses.

  The variable magnification optical system 1 includes only first to third lens groups 11, 12, and 13. For this reason, cost reduction and simplification of the optical total length can be achieved by simplifying the mechanical mechanism.

  In the variable magnification optical system 1, the negative meniscus lens 132 of the third lens group 13 is a resin material lens, and the variable magnification optical system 1 includes at least one resin material lens. For this reason, the negative meniscus lens 132 can be mass-produced with stable quality, and the cost can be reduced. The negative meniscus lens 132 is disposed in the third lens group 13. For this reason, it is possible to reduce the cost while minimizing the influence on the optical performance. From the same viewpoint, a lens made of a resin material may be further disposed on the image side with respect to the third lens group 13.

  In the variable magnification optical system 1, the second lens group 12 includes a positive lens 122 and a negative meniscus lens 123 that are cemented lenses. For this reason, it is possible to suppress the manufacturing error sensitivity of the second lens group 12, and it is possible to achieve both compactness and a reduction in manufacturing error sensitivity.

  In the variable magnification optical system 1 having such a configuration, the optical aperture 14 may be a mechanical shutter having a function of shielding light from the image sensor 16. Such a mechanical shutter is effective in preventing smear when, for example, a CCD element is used as the image sensor 16.

In the variable magnification optical system 1 having such a configuration, when the object distance is infinite, the distance on the optical axis from the surface vertex of the lens surface closest to the object side to the image plane at the wide angle end (however, the back focus is In the case of TLw as the air conversion length, it is preferable that the following conditional expression (2) is satisfied at the wide angle end in terms of off-axis aberration.
| Hg2 | / TLw> 0.01 (2)

By satisfying conditional expression (2), it is possible to effectively correct off-axis aberrations with the most object side lens of the second lens group 12. From the viewpoint of off-axis aberration and manufacturing error sensitivity, it is even more preferable that the variable magnification optical system 1 satisfies the following conditional expression (2 ′).
| Hg2 | / TLw> 0.05 (2 ')

  If the lower limit of conditional expression (2 ′) is not reached, the effect of correcting the off-axis aberration remaining in the first lens group 11 with the most object side lens in the second lens group 12 becomes weak. For this reason, in particular, the optical performance at the wide-angle end is deteriorated, or the manufacturing error sensitivity is increased when the optical performance is maintained.

In the variable magnification optical system 1 having such a configuration, when the refractive index of the negative lens 111 in the first lens group 11 is N1, and the Abbe number of the negative lens in the first lens group 11 is v1, the aberration From the viewpoint of correction, it is preferable that the negative lens 111 of the first lens group 11 satisfies the following conditional expressions (3) and (4).
N1 <1.65 (3)
v1> 50 (4)

When the upper limit of conditional expression (3) is exceeded, it becomes difficult to correct astigmatism occurring in the first lens group 11 with other lens groups, and when lower than the lower limit of conditional expression (4), It becomes difficult to correct lateral chromatic aberration generated in one lens group 11 with other lens groups. From the viewpoint of correcting astigmatism, the zoom optical system 1 more preferably satisfies the following conditional expression (3 ′). From the viewpoint of correcting lateral chromatic aberration, the zoom optical system 1 It is even more preferable to satisfy the formula (4 ′).
N1 <1.5 (3 ')
v1> 70 (4 ')

  In the variable magnification optical system 1, astigmatism is more sufficiently corrected by satisfying conditional expression (3 ′), and it is easier to correct lateral chromatic aberration by satisfying conditional expression (4 ′).

Further, in the variable magnification optical system 1 having such a configuration, when the combined focal length of the second lens group 12 is f2 and the combined focal length of the entire optical system at the wide angle end is fw, compactification and polarization are reduced. From the viewpoint of core error sensitivity, the second lens group 12 preferably satisfies the following conditional expression (5).
0.6 <f2 / fw <1.5 (5)

If the upper limit of conditional expression (5) is exceeded, the optical power of the second lens group 12 is too weak, and it becomes difficult to obtain a zoom ratio of about 2 to 3 times while ensuring compactness. If the lower limit of conditional expression (5) is not reached, the decentration error sensitivity of the second lens group 12 becomes very high, and the manufacture becomes difficult. In view of compactness, it is even more preferable that the variable magnification optical system 1 satisfies the following conditional expression (5 ′).
0.6 <f2 / fw <1.1 (5 ′)

  If the upper limit of conditional expression (5 ′) is exceeded, the optical power of the second lens group 12 will be weakened, and the amount of zoom movement will increase, resulting in an increase in the total optical length.

In the variable power optical system 1 having such a configuration, the refractive index of the most image side lens in the variable power optical system 1 is Ni, and the Abbe number of the most image side lens in the variable power optical system 1 is vi. In addition, from the viewpoint of off-axis light beam angle adjustment and lateral chromatic aberration correction, it is preferable that the most image side lens of the variable magnification optical system 1 satisfies the following conditional expressions (6) and (7).
1.5 <Ni (6)
vi <40 (7)

If the lower limit of conditional expression (6) is not reached, it is difficult to adjust the off-axis ray angle incident on the image plane, and if the upper limit of conditional expression (7) is exceeded, it corresponds to a high pixel imaging device. This makes it difficult to sufficiently correct the lateral chromatic aberration. From the viewpoint of correcting chromatic aberration of magnification, the zoom optical system 1 more preferably satisfies the following conditional expression (7 ′), and further preferably satisfies the following conditional expression (7 ″).
vi <35 (7 ')
By satisfying conditional expression (7 ′), the chromatic aberration of magnification is more sufficiently corrected.
vi <30 (7 ")

  By satisfying conditional expression (7 ″), it is possible to select a glass material having a relatively high refractive index as a usable glass material. This makes it easier to achieve both correction of lateral chromatic aberration and adjustment of the image plane incident angle.

Further, in the variable magnification optical system 1 having such a configuration, when the combined focal length of the third lens group 13 is set to f3, from the viewpoint of compactness and decentering error sensitivity, an object from infinity to a short-distance object is used. When performing focusing, it is preferable that the third lens group 13 moves and satisfies the following conditional expression (8).
0.8 <| f3 / fw | <1.5 (8)

  If the upper limit of conditional expression (8) is exceeded, the optical power of the third lens group 13 will be weakened, the amount of movement of the third lens group 13 will be increased in the case of focusing, and this will hinder compactization. If the lower limit of Expression (8) is not reached, the decentration error sensitivity of the third lens group 13 becomes very high, and the manufacture becomes difficult.

In the variable magnification optical system 1 having such a configuration, it is preferable that the following conditional expression (9) is satisfied when the maximum effective radius of the lens surface closest to the object in the variable magnification optical system is Rg1.
0.1 <Rg1 / TLw <0.3 (9)

If the upper limit of conditional expression (9) is exceeded, the cross-sectional area of the variable magnification optical system 1 increases, so that even if the total optical length is shortened, volume reduction of the variable magnification optical system 1 is hindered, and conditional expression (9) If the lower limit is exceeded, the optical power of the first lens group 11 becomes too strong, the decentration error sensitivity becomes very high, and the manufacture becomes difficult. From the viewpoint of volume reduction, it is even more preferable that the variable magnification optical system 1 satisfies the following conditional expression (9 ′).
0.15 <Rg1 / TLw <0.25 (9 ′)

  By satisfying conditional expression (9 ′), the volume of the variable magnification optical system 1 can be minimized.

In the variable magnification optical system 1 having such a configuration, the distance on the optical axis between the first lens group 11 and the second lens group 12 at the telephoto end is set to T12, and all the optical systems at the telephoto end are set. When the combined focal length is ft, it is preferable that the following conditional expression (10) is satisfied at the telephoto end from the viewpoint of the amount of zoom movement.
T12 / (fw × ft) ^1/2 <0.2 (10)

If the upper limit of the conditional expression (10) is exceeded, the substantial zooming movement amount of the second lens group 12 becomes small, so that the optical power of the second lens group 12 becomes strong and the manufacture becomes difficult. From the viewpoint of decentering error sensitivity, it is even more preferable that the variable magnification optical system 1 satisfies the following conditional expression (10 ′).
T12 / (fw × ft) ^1/2 <0.15 (10 ′)

  If the upper limit of conditional expression (10 ′) is exceeded, the optical power of each of the lenses 121 to 123 of the second lens group 12 increases, so that the eccentricity error sensitivity becomes high and adjustment between the lenses is necessary, or the accuracy is high. This is required and causes cost increase.

In the variable magnification optical system 1 having such a configuration, the curvature radius of the object side surface of the most object side lens in the second lens group is Rfg2, and the curvature radius of the image side surface of the most object side lens in the second lens group is In the case of Rrg, it is preferable that the most object side lens of the second lens group 12 satisfies the following conditional expression (11) from the viewpoint of manufacturing error sensitivity.
−0.4 <Rfg2 / Rrg2 <−0.2 (11)

  In general, when downsizing is performed, the optical power of each of the lenses 121 to 123 in the second lens group 12 is increased in order to suppress the movement amount of the zooming group, and as a result, the error sensitivity becomes too high and the manufacturing is performed. It becomes difficult. In particular, the most object side lens 121 has the strongest optical power in the second lens group 12. When the variable magnification optical system 1 satisfies the conditional expression (11), the manufacturing error sensitivity of the most object side lens 121 of the second lens group 12 can be suppressed.

In the variable magnification optical system 1 having such a configuration, when the back focus (air conversion length) at the telephoto end is set to Lb, the following conditional expression (12) is satisfied from the viewpoint of off-axis aberration correction and downsizing. It is preferable to satisfy.
1.0 <Lb / fw <1.5 (12)

  If the upper limit of conditional expression (12) is exceeded, the optical power of the negative lens in the first lens group 11 becomes too strong, and off-axis aberrations that occur in the first lens group 11 can be corrected by other lens groups. If it becomes difficult and the lower limit of conditional expression (12) is not reached, the zooming burden of the third lens group 13 is reduced, the optical total length is increased, and compactness is hindered.

In the variable magnification optical system 1 having such a configuration, it is preferable to further include a fourth lens group having positive optical power on the image side of the third lens group 13. By disposing the fourth lens group on the image side of the third lens group 14 in this way, it becomes possible to improve the telecentricity of the light incident on the imaging surface. When the variable magnification optical system 1 is composed of only the first to fourth lens groups, it is relatively easy to achieve both shortening of the optical total length and maintaining telecentricity. Furthermore, in the variable magnification optical system 1 further including the fourth lens group, it is preferable that the most object side lens of the second lens group 12 satisfies the following conditional expression (13).
0.3 <Rfg2 / Rrg2 <0.6 (13)

  In the case where the fourth lens group is further provided, it is possible to suppress the manufacturing error sensitivity of the most object side lens of the second lens group 12 by satisfying the conditional expression (13).

In the variable magnification optical system 1 having such a configuration, it is preferable that the following conditional expression (14) is satisfied.
0.2 <Lb / fw <0.4 (14)

  If the upper limit of conditional expression (14) is exceeded, the telecentricity of the off-axis ray incident angle on the image plane will be lost at the telephoto end, and the peripheral illuminance will decrease, which is not preferable, and the lower limit of conditional expression (14) If it is less than 1, the difference in off-axis light incident angle on the image plane at the wide-angle end and the telephoto end becomes too large, and the ambient illuminance is reduced at any point, which is not preferable.

In the variable magnification optical system 1 having such a configuration, it is preferable that the following conditional expression (15) is satisfied from the viewpoint of the variable magnification ratio and the manufacturing error sensitivity.
0.2 <f2 / ft <0.5 (15)

If the upper limit of conditional expression (15) is exceeded, the optical power of the second lens group 12 is too weak to obtain a zoom ratio of about 2 to 3 times, and the conditional expression (15) Below the lower limit, the manufacturing error sensitivity of the second lens group 12 becomes very high, and manufacturing becomes difficult. In view of the total optical length and the eccentricity error sensitivity, it is even more preferable that the variable magnification optical system 1 satisfies the following conditional expression (15 ′).
0.3 <f2 / ft <0.4 (15 ′)

  If the upper limit of conditional expression (15 ′) is exceeded, the optical power of the second lens group 12 is weak, so the amount of movement required for zooming by about 2 to 3 times increases and the optical total length becomes longer. If it is below the lower limit of the conditional expression (15 ′), the eccentric error sensitivity of the second lens group 12 becomes high and adjustment between lenses is required, or accuracy is required, and the cost increases. It becomes a factor of.

  In the variable magnification optical system 1 having such a configuration, it is preferable that the aperture stop is disposed on the image side with respect to the most image side lens surface of the second lens group 12. By disposing the aperture stop closer to the image side than the most image side lens surface of the second lens group 12, it is possible to correct off-axis aberrations.

  Further, in the variable magnification optical system 1 having such a configuration, in order from the object side to the image side, a first lens group including a negative lens, a positive biconvex lens or a convex positive lens on the object side, and a positive lens and a negative lens. It is preferable to include a second lens group including a cemented lens and a third lens group including one negative lens or two lenses of a negative lens and a positive lens in order from the object side. Composing the first lens group with one lens makes it easy to make it compact, and configuring the second lens group with three positive and negative lenses reduces the manufacturing error sensitivity with two positive lenses and adjusts the lens. It is possible to optimally balance the error sensitivity when performing the following steps, and the third lens group is constituted by a negative lens, a negative lens, or a positive lens, thereby shortening the total optical length and correcting astigmatism. It is possible to achieve both.

  Further, in the variable magnification optical system 1 having such a configuration, when a resin material lens is used, the lens is a lens molded using a material in which particles having a maximum length of 30 nanometers or less are dispersed in the resin material. Is preferred.

In general, mixing fine particles with a transparent resin material scatters light and reduces the transmittance, making it difficult to use as an optical material. However, the size of the fine particles should be smaller than the wavelength of the transmitted light beam. The light is not substantially scattered. And although a resin material will have a refractive index falling with a temperature rise, an inorganic particle will raise a refractive index with a temperature rise conversely. For this reason, it is possible to make the refractive index change hardly occur with respect to the temperature change by acting so as to cancel each other by utilizing such temperature dependency. More specifically, by dispersing inorganic fine particles having a maximum length of 30 nanometers or less in a resin material as a base material, a resin material with reduced temperature dependency of the refractive index is obtained. For example, fine particles of niobium oxide (Nb ₂ O ₅ ) are dispersed in acrylic. In the variable magnification optical system 1 having such a configuration, by using a lens made of a resin material in which such inorganic fine particles are dispersed for at least one lens, a back focus accompanying a change in environmental temperature of the variable magnification optical system 1 is achieved. It is possible to suppress the shift of the movement.

  Such a lens made of a resin material in which inorganic fine particles are dispersed is preferably molded as follows.

Describing the temperature change of the refractive index, the temperature change n (T) of the refractive index is expressed by Equation 16 by differentiating the refractive index n with respect to the temperature T based on the Lorentz-Lorentz equation.
n (T) = ((n2 + 2) × (n2-1)) / 6n × (−3α + (1 / [R]) × (∂ [R] / ∂T)) (16)
Where α is a linear expansion coefficient and [R] is molecular refraction.

In the case of a resin material, in general, the contribution of the refractive index to the temperature dependency is smaller in the second term than in the first term in Equation 16, and can be almost ignored. For example, in the case of PMMA resin, the linear expansion coefficient α is 7 × 10 ⁻⁵ , and when it is substituted into Equation 16, n (T) = − 1.2 × 10 ⁻⁴ (/ ° C.), which is an actual measurement value. Is approximately the same.

From the viewpoint of minimizing the back focus shift accompanying the environmental temperature change of the variable magnification optical system 1, the refractive index temperature change n (T) is preferably less than 8 × 10 ⁻⁵ (/ ° C.) in absolute value. Furthermore, the absolute value is preferably less than 6 × 10 ⁻⁵ (/ ° C.). When the refractive index temperature change n (T) is less than 6 × 10 ⁻⁵ (/ ° C.) in absolute value, the back focus shift amount accompanying the environmental temperature change of the variable magnification optical system 1 is approximately halved. It can be suppressed.

Therefore, as such a resin material, a polyolefin-based resin material or a polycarbonate-based resin material is preferable. In the polyolefin resin material, the refractive index temperature change n (T) is about −11 × 10 ⁻⁵ (/ ° C.), and in the polycarbonate resin material, the refractive index temperature change n (T) is about −14 × 10 ⁻⁵ (/ ° C.).

  In the variable magnification optical system 1 having such a configuration, a cam, a stepping motor, or the like may be used for driving the lens groups 11, 12, 13 and the optical diaphragm 14, or a piezoelectric actuator may be used. It may be used. In the case of using a piezoelectric actuator, it is possible to suppress an increase in the volume and power consumption of the driving device.

  In the variable magnification optical system 1 having such a configuration, it is preferable that all lens surfaces facing the air are aspherical surfaces. This configuration makes it possible to achieve both compactness and high image quality.

  In the variable magnification optical system 1 having such a configuration, the glass lens having an aspheric surface is a glass molded aspheric lens, a ground aspheric glass lens, a composite aspheric lens (aspheric shape on a spherical glass lens). Of the above resin). Glass molded aspherical lenses are preferable for mass production, and composite aspherical lenses have a high degree of design freedom because there are many glass materials that can serve as substrates. In particular, an aspherical lens using a high refractive index material is not easy to mold, so a composite aspherical lens is preferable.

  In the variable magnification optical system 1 having such a configuration, each of the lens groups 11, 12, and 13 is preferably composed of three or less lenses. With this configuration, the cost can be reduced by reducing the number of lenses.

  Further, in the variable magnification optical system 1 having such a configuration, two or more lenses may be formed of a resin material lens. With this configuration, it is possible to reduce costs and improve productivity.

<Description of digital equipment incorporating variable magnification optical system>
Next, a digital apparatus in which the above-described variable magnification optical system 1 is incorporated will be described.

  FIG. 2 is a block diagram illustrating a configuration of the digital device according to the embodiment. The digital device 3 includes an imaging unit 30, an image generation unit 31, an image data buffer 32, an image processing unit 33, a driving unit 34, a control unit 35, a storage unit 36, and an I / F unit 37 for the imaging function. Composed. Examples of the digital device 3 include a digital still camera, a video camera, a surveillance camera (monitor camera), a portable terminal such as a mobile phone or a personal digital assistant (PDA), a personal computer, and a mobile computer. Equipment (eg, a mouse, scanner, printer, etc.) may be included.

  The imaging unit 30 includes an imaging device 21 and an imaging element 16. The imaging device 21 includes a variable magnification optical system 1 as shown in FIG. 1 and a lens drive device (not shown) for driving the lens in the optical axis direction to perform variable magnification and focusing. Light rays from the subject are imaged on the light receiving surface of the image sensor 16 by the variable magnification optical system 1 and become an optical image of the subject.

  As described above, the imaging device 16 converts the optical image of the subject formed by the variable magnification optical system 1 into an electrical signal (image signal) of R, G, B color components, and each color of R, G, B To the image generation unit 31 as an image signal. The imaging device 16 is controlled by the control unit 35 for imaging operations such as imaging of either a still image or a moving image, or reading (horizontal synchronization, vertical synchronization, transfer) of the output signal of each pixel in the imaging device 16. .

  The image generation unit 31 performs amplification processing, digital conversion processing, and the like on the analog output signal from the image sensor 16 and determines an appropriate black level, γ correction, and white balance adjustment (WB adjustment) for the entire image. Then, known image processing such as contour correction and color unevenness correction is performed to generate image data of each pixel from the image signal. The image data generated by the image generation unit 31 is output to the image data buffer 32.

  The image data buffer 32 is a memory that temporarily stores image data and is used as a work area for performing processing described later on the image data by the image processing unit 33. For example, the image data buffer 32 is a volatile storage element. It is composed of a RAM (Random Access Memory).

  The image processing unit 33 is a circuit that performs image processing such as resolution conversion on the image data in the image data buffer 32. It is also possible to configure the image processing unit 33 to correct aberrations that could not be corrected by the variable magnification optical system 1 as necessary.

  The driving unit 34 operates one or a plurality of zooming optical systems 1 to perform desired zooming and focusing by operating the lens driving device (not shown) based on a control signal output from the control unit 35. Drive the lens group.

  The control unit 35 includes, for example, a microprocessor and its peripheral circuits, and includes an imaging unit 30, an image generation unit 31, an image data buffer 32, an image processing unit 33, a drive unit 34, a storage unit 36, and an I / F unit. The operation of each part 37 is controlled according to its function. In other words, the imaging device 21 is controlled by the control unit 35 to execute at least one of the still image shooting and the moving image shooting of the subject.

  The storage unit 36 is a storage circuit that stores image data generated by still image shooting or moving image shooting of a subject. For example, a ROM (Read Only Memory) that is a nonvolatile storage element or a rewritable nonvolatile memory It comprises an EEPROM (Electrically Erasable Programmable Read Only Memory) that is a storage element, a RAM, and the like. That is, the storage unit 36 has a function as a still image memory and a moving image memory.

  The I / F unit 37 is an interface that transmits / receives image data to / from an external device. For example, the I / F unit 37 is an interface that conforms to a standard such as USB or IEEE1394.

  Next, the imaging operation of the digital device 3 having such a configuration will be described.

  When shooting a still image, the control unit 35 controls the imaging device 21 to shoot a still image and operates the lens driving device (not shown) of the imaging device 21 via the driving unit 34. , Do the focusing. As a result, the focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 16, converted into R, G, and B color component image signals, and then output to the image generation unit 31. . The image signal is temporarily stored in the image data buffer 32, and after image processing is performed by the image processing unit 33, an image based on the image signal is displayed on a display (not shown). The photographer can adjust the main subject so as to be within a desired position on the screen by referring to the display. When a so-called shutter button (not shown) is pressed in this state, image data is stored in the storage unit 36 as a still image memory, and a still image is obtained.

  In this case, when zoom shooting is performed to magnify the subject at a position away from the imaging device 21 or near the subject, the control unit 35 executes lens driving for zooming and zooming The optical system 1 is continuously zoomed. As a result, by adjusting the enlargement ratio even for a subject far from the photographer, the main subject can be adjusted to fit in the desired position on the screen, and enlarged An image can be obtained.

  In addition, when performing moving image shooting, the control unit 35 controls the imaging device 21 to perform moving image shooting. After that, as in the case of still image shooting, the photographer refers to the display (not shown) so that the image of the subject obtained through the imaging device 21 is placed at a desired position on the screen. Can be adjusted. In this case, similarly to still image shooting, the enlargement ratio of the subject image can be adjusted, and moving image shooting is started by pressing the shutter button (not shown). It is also possible to change the magnification rate of the subject at any time during the photographing.

  At the time of moving image shooting, the control unit 35 controls the imaging device 21 to shoot a moving image and operates the lens driving device (not shown) of the imaging device 21 via the driving unit 34 to perform focusing. As a result, a focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 16, converted into image signals of R, G, and B color components, and then output to the image generation unit 31. . The image signal is temporarily stored in the image data buffer 32, and after image processing is performed by the image processing unit 33, an image based on the image signal is displayed on a display (not shown). Then, when the shutter button (not shown) is pressed again, the moving image shooting is completed. The captured moving image is guided to and stored in the storage unit 36 as a moving image memory.

  Since the imaging apparatus 21 and the digital apparatus 3 include the variable magnification optical system 1 that is compact but can correct various aberrations such as spherical aberration, chromatic aberration, and astigmatism as compared with the background art, The image pickup device 16 having a high pixel can be employed while reducing the size. In particular, since the variable magnification optical system 1 is small and can be applied to a high-pixel image pickup device, it is suitable for a mobile terminal that is increasing in pixel count and functionality. As an example, a case where the imaging device 21 is mounted on a mobile phone will be described below.

  FIG. 3 is an external configuration diagram of a camera-equipped cellular phone showing an embodiment of a digital device. 3A shows an operation surface of the mobile phone, and FIG. 3B shows a back surface of the operation surface, that is, a back surface.

  In FIG. 3, the mobile phone 5 is provided with an antenna 51 at the top, and on its operation surface, as shown in FIG. 3A, a rectangular display 52, activation of image shooting mode, still image shooting and moving image An image shooting button 53 for switching to shooting, a zoom button 54 for controlling zooming (zooming), a shutter button 55, and a dial button 56 are provided.

  The cellular phone 5 incorporates a circuit for realizing a telephone function using a cellular phone network, and includes the above-described imaging unit 30, image generating unit 31, image data buffer 32, image processing unit 33, and driving unit. 34, the control part 35, and the memory | storage part 36 are incorporated, and the imaging device 21 of the imaging part 30 faces the back.

  When the image capturing button 53 is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 executes an operation corresponding to the operation content. The scaling button 54 is constituted by, for example, a two-contact switch, and the upper end portion thereof is printed with “T” representing telephoto and the lower end portion is printed with “W” representing wide angle. When the printing position of the scaling button 54 is pressed, a control signal indicating each scaling operation is output to the control unit 35, and the control unit 35 executes an operation corresponding to the scaling operation. When the shutter button 55 is operated, a control signal indicating the operation content is output to the control unit 35, and the control unit 35 performs an operation corresponding to the operation content.

<Description of More Specific Embodiment of Variable-Magnification Optical System>
A specific configuration of the variable power optical system 1 as shown in FIG. 1, that is, the variable power optical system 1 provided in the imaging device 21 mounted in the digital device 3 as shown in FIG. This will be described with reference to FIG.

  FIG. 4 is a cross-sectional view showing the arrangement of lens groups in the variable magnification optical system in the first embodiment. FIG. 9 is a diagram showing how the lens groups move during zooming. W indicates the case at the wide-angle end, M indicates the case at the intermediate point, and T indicates the case at the telephoto end. FIG. 9 shows not only the case of the first embodiment but also the case of a fourth embodiment described later. FIG. 11 is an aberration diagram of the lens unit at the wide-angle end according to Example 1. FIG. 12 is an aberration diagram of the lens unit at the midpoint of Example 1. FIG. 13 is an aberration diagram of the lens unit at the telephoto end according to Example 1.

  As shown in FIG. 4, the variable magnification optical system 1 </ b> A of Example 1 includes a first lens group in which each lens group (Gr1, Gr2, Gr3) has negative optical power as a whole in order from the object side to the image side. (Gr1), a second lens group (Gr2) having a positive optical power as a whole, an optical aperture stop ST, and a third lens group (Gr3) having a negative optical power as a whole. A negative three-component zoom configuration, and during zooming, as shown in FIG. 9, the first lens group (Gr1) is fixed, and the second lens group (Gr2) and the third lens group (Gr3) And the optical aperture stop ST moves together with the second lens group (Gr2).

  More specifically, in the variable magnification optical system 1A of Example 1, each lens group (Gr1, Gr2, Gr3) is configured as follows in order from the object side to the image side.

  The first lens group (Gr1) is composed of a biconcave negative lens (first lens L1).

  The second lens group (Gr2) includes a biconvex positive lens (second lens L2), a biconvex positive lens (third lens L3), and a negative meniscus lens (fourth lens L4) convex on the image side. The second lens L2 has two aspheric surfaces, and is a resin material lens, for example. The second lens L2 may be, for example, a glass mold aspheric lens. For example, forming with a glass mold aspherical lens is preferable because the degree of freedom in selecting a glass material having a high refractive index and a glass material having a low dispersion increases, and the degree of freedom in aberration correction increases. The third lens L3 and the fourth lens L4 are cemented lenses.

  The third lens group (Gr3) includes a negative meniscus lens (fifth lens L5) convex toward the object side and a negative meniscus lens (sixth lens L6) convex toward the object side. The sixth lens L6 has two aspheric surfaces, and is, for example, a resin material lens.

  On the image side of the second lens group (Gr2), the optical aperture stop ST is arranged so as to move together with the second lens group (Gr2). Then, on the image side of the third lens group (Gr3), the light receiving surface of the image sensor SR is disposed via a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In FIG. 4, the number ri (i = 1, 2, 3,...) Given to each lens surface is the i-th lens surface when counted from the object side. It is assumed that a surface marked with “*” in ri is an aspherical surface. The optical diaphragm ST, both surfaces of the parallel plate FT, and the light receiving surface of the image sensor SR are also handled as one surface. The meaning of such handling and symbols is the same for Examples 2 to 5 described later (FIGS. 5 to 8). However, it does not mean that they are exactly the same. For example, in FIGS. 4 to 8 of each of the first to fifth embodiments, the lens surface arranged closest to the object side is assigned the same symbol (r1). However, this does not mean that these curvatures are the same throughout the first to fifth embodiments.

  Under such a configuration, a light beam incident from the object side sequentially has a first lens group (Gr1), a second lens group (Gr2), an optical aperture stop ST, and a third lens group (Gr3) along the optical axis AX. ) And the parallel plate FT, and an optical image of the object is formed on the light receiving surface of the image sensor SR. In the image sensor SR, the optical image is converted into an electrical signal. This electrical signal is subjected to predetermined digital image processing as necessary, and recorded as a digital video signal, for example, in a memory of a digital device such as a digital camera or transmitted to another digital device by wired or wireless communication. Or

  In the zoom optical system 1A of the first embodiment, as shown in FIG. 9, the first lens group (Gr1) is in the zooming from the wide angle end (W) to the telephoto end (T) through the middle (M). The second lens group (Gr2) is linearly moved in a direction approaching the object, the optical aperture stop ST is moved together with the second lens group (Gr2), and the third lens group (Gr3) is Is moved in a curvilinear direction (curve that is convex toward the object side). Thus, in zooming from the wide-angle end (W) to the telephoto end (T), the first lens group (Gr1) and the second lens group (Gr2) move so that the distance between them becomes narrow.

  The construction data of each lens in the variable magnification optical system 1A of Example 1 is shown below.

Numerical example 1
Unit mm
Surface data surface number r d nd νd
Surface ∞ Variable 1 -24.260 0.500 1.63854 55.43
2 6.606 Variable 3 * 4.344 2.469 1.58913 61.24
4 * -14.558 1.000
5 12.354 1.599 1.58913 61.24
6 -3.937 0.694 1.80518 25.46
7 -7.824 0.100
8 (Aperture) ∞ Variable 9 41.692 0.500 1.48749 70.45
10 3.463 0.987
11 * 7.844 0.955 1.60700 27.10
12 * 6.428 Variable 13 ∞ 0.500 1.51680 64.20
14 ∞ 0.558
Image plane ∞
Aspheric data 3rd surface K = 0.000000 + 00, A4 = -1.64290E-03, A6 = -3.19260E-05, A8 = -4.62610E-06, A10 = 4.40630E-07
4th surface K = 0.00000E + 00, A4 = 5.03200E-04, A6 = 3.06090E-06, A8 = 4.18580E-06, A10 = 1.14100E-07
11th surface K = 0.00000E + 00, A4 = -1.86660E-02, A6 = 1.36960E-04, A8 = 6.34070E-04, A10 = -1.48570E-04
12th surface K = 0.00000E + 00, A4 = -1.88730E-02, A6 = 1.06400E-03, A8 = 6.78240E-05, A10 = -1.98940E-05
Various data zoom data Zoom ratio 2.78
Wide angle Medium Telephoto focal length 5.080 8.415 14.104
F number 3.256 4.855 7.117
Angle of view 35.323 23.160 14.319
Image height 3.600 3.600 3.600
Total lens length 16.867 16.867 16.867
BF 1.694 4.488 6.330
d2 5.381 3.096 0.500
d8 0.987 0.479 1.232
d12 0.807 3.600 5.443
Zoom lens group data group Start surface End surface Focal length 1 1 2 -8.080
2 3 8 4.747
3 9 12 -6.667
In the above surface data, the surface number corresponds to the number i of the symbol ri (i = 1, 2, 3,...) Given to each lens surface shown in FIG. The surface marked with * in the number i indicates an aspherical surface (aspherical refractive optical surface or a surface having a refractive action equivalent to an aspherical surface).

  Also, “r” is the radius of curvature of each surface (unit is mm), “d” is the distance between the lens surfaces on the optical axis in the infinite focus state (axis upper surface distance), and “nd” is The refractive index “νd” of each lens with respect to the d-line (wavelength 587.56 nm) indicates the Abbe number. Since each surface of the optical aperture stop ST, both surfaces of the parallel flat plate FT, and the light receiving surface of the image sensor SR is a flat surface, the radius of curvature thereof is ∞ (infinite).

The above-mentioned aspheric surface data includes the quadric surface parameter (cone coefficient K) and the aspheric surface coefficient Ai (i = 4, 6, 6) of the surface that is an aspheric surface (the surface with the number i added to * in the surface data). 8, 10, 12). The aspherical shape of the optical surface is defined by the following equation using a local orthogonal coordinate system (x, y, z) in which the surface vertex is the origin and the direction from the object toward the image sensor is the positive z-axis direction. doing.
z (h) = ch ² / [1 + √ {1− (1 + K) c ² h ² }] + ΣAi · hi
However, z (h): Amount of displacement in the z-axis direction at the position of height h (based on the surface vertex)
h: height in a direction perpendicular to the z-axis (h ² = x ² + y ² )
c: Paraxial curvature (= 1 / radius of curvature)
Ai: i-th order aspheric coefficient
K: quadratic surface parameter (cone coefficient)
Each aberration in the variable magnification optical system 1A of Example 1 under the lens arrangement and configuration as described above is shown in FIGS. 11, 12 and 13, respectively. 11 shows each aberration at the wide angle end (W), FIG. 12 shows each aberration at the intermediate point (M), and FIG. 13 shows each aberration at the telephoto end (T). 11A, 12A, and 13A, in order from the left, spherical aberration (sine condition) (LONGITUDINAL SPHERICAL ABERRATION), astigmatism (ASTIGMATIC FIELD CURVER), and distortion (DISTORTION) ) Respectively. The abscissa of the spherical aberration represents the focal position deviation in mm, and the ordinate represents the value normalized by the incident height. The horizontal axis of astigmatism represents the focal position shift in mm, and the vertical axis represents the image height in mm. The horizontal axis of the distortion aberration represents the actual image height as a percentage (%) with respect to the ideal image height, and the vertical axis represents the image height in mm. Moreover, in the figure of astigmatism, the broken line represents the result on the tangential (meridional) surface, and the solid line represents the result on the sagittal (radial) surface.

  11 (B), 12 (B), and 13 (B) show lateral aberration, the left side shows a TANGENTIAL (meridional) plane, and the right side shows SAGITAL (radial). The case of a surface is shown, and the case of the maximum field angle, the case of an intermediate field angle, and the case of an axis are respectively shown from the top. The horizontal axis of the lateral aberration represents the height of the incident light with respect to the principal ray in mm, and the vertical axis represents the deviation from the principal ray on the image plane in mm.

  In the spherical aberration and lateral aberration diagrams, three light aberrations, d-line (wavelength 587.56 nm) with a solid line, g-line (wavelength 435.84 nm) with a broken line, and C-line (wavelength 656.28 nm) with a dashed-dotted line, are shown. Each is shown. The diagrams of astigmatism and distortion are the results when the d-line (wavelength 587.56 nm) is used.

  The above handling is the same in the construction data according to Examples 2 to 5 shown below and FIGS. 14 to 25 showing the respective aberrations.

  FIG. 5 is a cross-sectional view illustrating the arrangement of lens groups in the variable magnification optical system according to the second embodiment. FIG. 10 is a diagram illustrating how the lens groups move during zooming. W indicates the case at the wide-angle end, M indicates the case at the intermediate point, and T indicates the case at the telephoto end. FIG. 10 shows not only the case of the second embodiment but also the cases of a third embodiment and a fifth embodiment described later. FIG. 14 is an aberration diagram of the lens unit at the wide-angle end according to Example 2. FIG. 15 is an aberration diagram of the lens unit at the intermediate point in Example 2. FIG. 16 is an aberration diagram of the lens unit at the telephoto end according to Example 2.

  The variable magnification optical system 1B of Example 2 includes a first lens group (Gr1) in which each lens group (Gr1, Gr2, Gr3, Gr4) has negative optical power as a whole in order from the object side to the image side. A second lens group (Gr2) having a positive optical power as a whole, an optical stop ST (not shown), a third lens group (Gr3) having a negative optical power as a whole, and a positive optical as a whole This is a negative / positive / negative / positive four-component zoom configuration including a fourth lens group (Gr4) having power, and during zooming, as shown in FIG. 10, the first lens group (Gr1) and the first lens group (Gr4) The fourth lens group (Gr4) is fixed, the second lens group (Gr2) and the third lens group (Gr3) are moved, and the optical aperture stop ST is moved together with the second lens group (Gr2).

  More specifically, in the variable magnification optical system 1B of Example 2, each lens group (Gr1, Gr2, Gr3, Gr4) is configured as follows in order from the object side to the image side.

  The first lens group (Gr1) is composed of a biconcave negative lens (first lens L1). The first lens L1 has two aspheric surfaces.

  The second lens group (Gr2) includes a positive meniscus lens convex to the object side (second lens L2), a positive biconvex lens (third lens L3), and a negative meniscus lens convex to the image side (fourth lens L4). Consists of. The second lens L2 has two aspheric surfaces. The third lens L3 and the fourth lens L4 are cemented lenses.

  The third lens group (Gr3) is composed of a negative meniscus lens (fifth lens L5) convex toward the image side. The fifth lens L5 has two aspheric surfaces.

  The fourth lens group (Gr4) is composed of a positive meniscus lens (sixth lens L6) convex toward the image side. The sixth lens L6 has two aspheric surfaces, and is, for example, a resin material lens.

  On the image side of the second lens group (Gr2), the optical diaphragm ST (not shown) is arranged so as to move together with the second lens group (Gr2). Then, on the image side of the fourth lens group (Gr4), the light receiving surface of the image sensor SR is arranged via a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In the variable magnification optical system 1B of the second embodiment, as shown in FIG. 10, the first lens group (Gr1) at the time of zooming from the wide angle end (W) to the telephoto end (T) through the intermediate point (M). Is fixed, the second lens group (Gr2) is linearly moved in the direction approaching the object, the optical aperture stop ST is moved together with the second lens group (Gr2), and the third lens group (Gr3) is The fourth lens group (Gr4) is fixed by moving linearly in a direction approaching the object while bending at the intermediate point (M). Thus, in zooming from the wide-angle end (W) to the telephoto end (T), the first lens group (Gr1) and the second lens group (Gr2) move so that the distance between them becomes narrow.

  The construction data of each lens in the variable magnification optical system 1B of Example 2 is shown below.

Numerical example 2
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 * -31.582 0.800 1.48749 70.45
2 * 2.971 Variable 3 * 4.814 1.115 1.68893 31.16
4 * 12.311 0.772
5 3.566 1.419 1.49700 81.61
6 -3.000 0.898 1.80518 25.46
7 (Aperture) -4.216 Variable 8 * -2.248 0.612 1.80518 25.46
9 * -7.266 Variable 10 * -9.301 2.409 1.60700 27.10
11 * -3.081 0.740
12 ∞ 0.3000 1.51680 64.20
13 ∞ 0.540
Image plane ∞
Aspheric data 1st surface K = 0.000000 + 00, A4 = -4.30750E-04, A6 = 1.28310E-04, A8 = -1.19050E-05, A10 = 3.886730E-07
Second surface K = 0.00000E + 00, A4 = -1.06110E-03, A6 = -1.74300E-04, A8 = 1.47710E-05. A10 = -8.13400E-06
3rd surface K = 0.00000E + 00, A4 = 4.01850E-03, A6 = 6.35570E-04, A8 = -8.52930E-05, A10 = 2.23090E-05
4th surface K = 0.00000E + 00, A4 = 6.88740E-03, A6 = 1.47210E-03, A8 = -3.06720E-04, A10 = 9.46280E-05
8th surface K = -1.00000E + 00, A4 = 2.6580E-02, A6 = -2.61500E-03, A8 = -2.73250E-03, A10 = 6.14200E-04
9th surface K = -1.00000E + 00, A4 = 3.08990E-02, A6 = -1.55140E-03, A8 = -9.22300E-04, A10 = 1.64140E-04
10th surface K = -1.00000E + 00, A4 = 5.30140E-04, A6 = -4.36910E-04, A8 = 5.05870E-05, A10 = -1.36730E-06
11th surface K = -1.00000E + 00, A4 = 3.83340E-03, A6 = -4.98730E-04, A8 = 1.80110E-05, A10 = 1.26540E-07
Various data zoom data Zoom ratio 2.73
Wide angle Medium Telephoto focal length 4.400 7.682 12.001
F number 3.658 5.339 7.100
Angle of view 40.815 26.320 17.570
Image height 3.800 3.800 3.800
Total lens length 18.938 18.938 18.937
BF 1.477 1.477 1.477
d2 6.067 3.415 1.396
d7 1.764 2.002 2.818
d9 1.604 4.018 5.221
d13 0.540 0.540 0.539
Zoom lens group data group Start surface End surface Focal length 1 1 2 -5.528
2 3 7 3.980
3 8 9 -4.276
4 10 11 6.620
The spherical aberration (sine condition), astigmatism, distortion, and lateral aberration in the variable magnification optical system 1B of Example 2 under the lens arrangement and configuration as described above are shown in FIGS. Respectively. 14 shows each aberration at the wide-angle end (W), FIG. 15 shows each aberration at the intermediate point (M), and FIG. 16 shows each aberration at the telephoto end (T).

  FIG. 6 is a cross-sectional view illustrating the arrangement of lens groups in the variable magnification optical system according to the third embodiment. FIG. 17 is an aberration diagram of the lens unit at the wide-angle end according to Example 3. FIG. 18 is an aberration diagram of the lens unit at the midpoint of Example 3. FIG. 19 is an aberration diagram of the lens unit at the telephoto end according to Example 3.

  The variable magnification optical system 1C of Example 3 includes a first lens group (Gr1) in which each lens group (Gr1, Gr2, Gr3, Gr4) has negative optical power as a whole in order from the object side to the image side. A second lens group (Gr2) having a positive optical power as a whole, an optical aperture stop ST, a third lens group (Gr3) having a negative optical power as a whole, and a positive optical power as a whole. The zoom lens has a negative / positive / negative / positive four-component zoom configuration including the fourth lens group (Gr4). As shown in FIG. 10, the first lens group (Gr1) and the fourth lens group are used during zooming. (Gr4) is fixed, the second lens group (Gr2) and the third lens group (Gr3) move, and the optical aperture stop ST moves together with the second lens group (Gr2).

  More specifically, in the variable magnification optical system 1C of Example 3, each lens group (Gr1, Gr2, Gr3, Gr4) is configured as follows in order from the object side to the image side.

  The first lens group (Gr1) is composed of a biconcave negative lens (first lens L1). The first lens L1 has two aspheric surfaces.

  The second lens group (Gr2) includes a positive meniscus lens convex to the object side (second lens L2), a positive biconvex lens (third lens L3), and a negative meniscus lens convex to the image side (fourth lens L3). Consists of. The second lens L2 has two aspheric surfaces. The third and fourth lenses L3 and L4 are single-sided aspheric lenses. The third lens L3 and the fourth lens L4 are cemented lenses.

  The third lens group (Gr3) is composed of a negative meniscus lens (fifth lens L5) convex toward the image side. The fifth lens L5 has two aspheric surfaces.

  The fourth lens group (Gr4) is composed of a positive meniscus lens (sixth lens L6) convex toward the image side. The sixth lens L6 has two aspheric surfaces, and is, for example, a resin material lens.

  On the image side of the second lens group (Gr2), the optical aperture stop ST is arranged so as to move together with the second lens group (Gr2). Then, on the image side of the fourth lens group (Gr4), the light receiving surface of the image sensor SR is arranged via a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In the variable magnification optical system 1C of the third embodiment, as shown in FIG. 10, at the time of zooming from the wide angle end (W) to the telephoto end (T) through the intermediate point (M), the first lens group (Gr1) Is fixed, the second lens group (Gr2) is linearly moved in the direction approaching the object, the optical aperture stop ST is moved together with the second lens group (Gr2), and the third lens group (Gr3) is The fourth lens group (Gr4) is fixed by moving linearly in a direction approaching the object while bending at the intermediate point (M). Thus, in zooming from the wide-angle end (W) to the telephoto end (T), the first lens group (Gr1) and the second lens group (Gr2) move so that the distance between them becomes narrow.

  The construction data of each lens in the variable magnification optical system 1C of Example 3 is shown below.

Numerical Example 3
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 * -14.565 0.800 1.49700 81.61
2 * 3.536 Variable 3 * 5.034 1.345 1.77502 47.83
4 * 13.473 1.887
5 * 3.987 1.486 1.49700 81.61
6 -3.052 0.897 1.80518 25.46
7 * -4.306 0.100
8 (Aperture) ∞ Variable 9 * -2.609 0.600 1.69310 37.40
10 * -17.038 Variable 11 * -12.620 2.050 1.58340 30.23
12 * -3.454 0.500
13 ∞ 0.3000 1.51680 64.20
14 ∞ 0.538
Image plane ∞
Aspheric data 1st surface K = 0.000000 + 00, A4 = 9.12840E-05, A6 = 8.81860E-05, A8 = -6.68400E-06, A10 = 1.42570E-07
Second surface K = 0.00000E + 00, A4 = -1.09860E-03, A6 = -4.76200E-05, A8 = 2.12090E-05, A10 = -3.94890E-06
Third surface K = 0.00000E + 00, A4 = 3.02580E-04, A6 = -2.46500E-05, A8 = 3.30410E-05, A10 = -4.67630E-07
4th surface K = 0.00000E + 00, A4 = 7.49640E-04, A6 = 1.22710E-05, A8 = 7.96580E-05, A10 = -2.10300E-06
5th surface K = 0.00000E + 00, A4 = -3.64720E-03, A6 = -7.02560E-04, A8 = 2.47930E-04, A10 = -5.63210E-05
7th surface K = 0.00000E + 00, A4 = -7.38510E-04, A6 = -5.73940E-05, A8 = -3.98740E-06, A10 = 4.06880E-06
9th surface K = -1.00000E + 00, A4 = 1.08980E-03, A6 = 1.25700E-02, A8 = -8.51470E-03, A10 = 1.76440E-03
10th surface K = -1.00000E + 00, A4 = 1.69990E-02, A6 = 6.28370E-03, A8 = -2.91340E-03, A10 = 4.11370E-04
11th surface K = -1.00000E + 00, A4 = -1.13490E-03, A6 = -6.24460E-04, A8 = 9.41400E-05, A10 = -2.83160E-06
12th surface K = -1.00000E + 00, A4 = 4.22860E-03, A6 = -7.42800E-04, A8 = 3.02430E-05, A10 = 5.77310E-07
Various data zoom data Zoom ratio 2.74
Wide angle intermediate telephoto focal length 4.522 7.910 12.392
F number 3.385 5.143 7.100
Angle of View 40.043 25.660 17.047
Image height 3.800 3.800 3.800
Total lens length 18.936 18.936 18.936
BF 1.236 1.236 1.236
d2 5.438 2.782 0.639
d8 1.908 2.197 3.302
d10 1.189 3.555 4.594
Zoom lens group data group Start surface End surface Focal length 1 1 2 -5.642
2 3 8 4.562
3 9 10 -4.522
4 11 12 7.532
The spherical aberration (sine condition), astigmatism, distortion and lateral aberration in the variable magnification optical system 1C of Example 3 under the lens arrangement and configuration as described above are shown in FIGS. Respectively. 17 represents each aberration at the wide-angle end (W), FIG. 18 represents each aberration at the intermediate point (M), and FIG. 19 represents each aberration at the telephoto end (T).

  FIG. 7 is a cross-sectional view illustrating the arrangement of lens groups in the variable magnification optical system according to the fourth embodiment. FIG. 20 is an aberration diagram of the lens unit at the wide-angle end according to Example 4. FIG. 21 is an aberration diagram of a lens unit at an intermediate point in Example 4. FIG. 22 is an aberration diagram of the lens unit at the telephoto end according to the fourth embodiment.

  As shown in FIG. 7, the variable magnification optical system 1D of the fourth embodiment includes a first lens group in which each lens group (Gr1, Gr2, Gr3) has negative optical power as a whole in order from the object side to the image side. (Gr1), a second lens group (Gr2) having a positive optical power as a whole, an optical aperture stop ST, and a third lens group (Gr3) having a negative optical power as a whole. A negative three-component zoom configuration, and during zooming, as shown in FIG. 9, the first lens group (Gr1) is fixed, and the second lens group (Gr2) and the third lens group (Gr3) And the optical aperture stop ST moves together with the second lens group (Gr2).

  More specifically, in the variable magnification optical system 1D of Example 4, each lens group (Gr1, Gr2, Gr3) is configured as follows in order from the object side to the image side.

  The first lens group (Gr1) is composed of a biconcave negative lens (first lens L1).

  The second lens group (Gr2) includes a biconvex positive lens (second lens L2) and a negative meniscus lens (third lens L3) convex on the image side. The second and third lenses L2, L3 are aspheric on both sides.

  The third lens group (Gr3) includes a negative meniscus lens (fourth lens L4) convex toward the object side and a positive meniscus lens (fifth lens L5) convex toward the object side. The fifth lens L5 has two aspheric surfaces, and is a resin material lens, for example.

  On the image side of the second lens group (Gr2), the optical aperture stop ST is arranged so as to move together with the second lens group (Gr2). Then, on the image side of the third lens group (Gr3), the light receiving surface of the image sensor SR is disposed via a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In the zoom optical system 1D of Embodiment 4, when zooming from the wide angle end (W) to the telephoto end (T) through the middle (M), the first lens group (Gr1) is as shown in FIG. The second lens group (Gr2) is linearly moved in a direction approaching the object, the optical aperture stop ST is moved together with the second lens group (Gr2), and the third lens group (Gr3) is Is moved in a curvilinear direction (curve that is convex toward the object side). Thus, in zooming from the wide-angle end (W) to the telephoto end (T), the first lens group (Gr1) and the second lens group (Gr2) move so that the distance between them becomes narrow.

  The construction data of each lens in the variable magnification optical system 1D of Example 4 is shown below.

Numerical Example 4
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 -9.097 0.600 1.49700 81.61
2 14.443 Variable 3 * 2.995 1.757 1.58913 61.24
4 * -10.654 0.300
5 * -9.257 0.978 1.82184 23.25
6 * -152.329 0.837
7 (Aperture) ∞ Variable 8 14.352 0.600 1.48749 70.45
9 4.097 1.450
10 * 6.284 0.600 1.60700 27.10
11 * 6.967 Variable 12 ∞ 0.500 1.51680 64.20
13 ∞ 0.549
Image plane ∞
Aspheric data 3rd surface K = 0.00000E + 00, A4 = -1.11540E-03, A6 = -2.666330E-05, A8 = -3.54200E-05, A10 = 1.02070E-06
4th surface K = 0.00000E + 00, A4 = 2.74860E-03, A6 = 7.81740E-05, A8 = 2.08550E-05, A10 = -2.06030E-06
5th surface K = 0.00000E + 00, A4 = 6.28480E-03, A6 = 6.45850E-04, A8 = -2.30860E-05, A10 = -6.12960E-06
6th surface K = 0.00000E + 00, A4 = 1.84450E-02, A6 = 2.00890E-03, A8 = -3.16080E-04, A10 = 1.37720E-04
10th surface K = 0.00000E + 00, A4 = -1.44380E-02, A6 = 1.72190E-03, A8 = -2.16800E-04, A10 = -5.15960E-06
11th surface K = 0.00000E + 00, A4 = -1.62580E-02, A6 = 1.57780E-03, A8 = -1.85610E-04, A10 = 8.87260E-08
Various data zoom data Zoom ratio 2.77
Wide angle Medium telephoto focal length 6.168 10.218 17.098
F number 3.445 5.013 7.100
Angle of view 30.271 19.408 11.890
Image height 3.600 3.600 3.600
Total lens length 16.879 16.879 16.879
BF 1.232 5.707 7.966
d2 6.347 3.585 0.500
d7 2.177 0.464 1.290
d11 0.353 4.828 7.087
Zoom lens group data group Start surface End surface Focal length 1 1 2 -11.136
2 3 7 5.548
3 8 11 -13.858
The spherical aberration (sine condition), astigmatism, distortion and lateral aberration in the variable magnification optical system 1D of Example 4 under the lens arrangement and configuration as described above are shown in FIGS. 20, 21, and 22. Respectively. 20 shows each aberration at the wide angle end (W), FIG. 21 shows each aberration at the intermediate point (M), and FIG. 22 shows each aberration at the telephoto end (T).

  FIG. 8 is a cross-sectional view showing the arrangement of lens groups in the variable magnification optical system in the fifth embodiment. FIG. 23 is an aberration diagram of the lens unit at the wide-angle end according to Example 5. FIG. 24 is an aberration diagram of the lens unit at the intermediate point according to Example 5. FIG. 25 is an aberration diagram of the lens unit at the telephoto end according to Example 5.

  The variable magnification optical system 1E of Example 5 includes a first lens group (Gr1) in which each lens group (Gr1, Gr2, Gr3, Gr4) has negative optical power as a whole in order from the object side to the image side. A second lens group (Gr2) having a positive optical power as a whole, a third lens group (Gr3) having a negative optical power as a whole, and a fourth lens group having a positive optical power as a whole ( Gr4) is a negative / positive / negative / positive four-component zoom configuration. During zooming, as shown in FIG. 10, the first lens group (Gr1) and the fourth lens group (Gr4) It is fixed and the second lens group (Gr2) and the third lens group (Gr3) move.

  More specifically, in the variable magnification optical system 1E of Example 5, each lens group (Gr1, Gr2, Gr3, Gr4) is configured as follows in order from the object side to the image side.

  The first lens group (Gr1) is composed of a biconcave negative lens (first lens L1). The first lens L1 has two aspheric surfaces.

  The second lens group (Gr2) includes a positive meniscus lens convex on the object side (second lens L2), an optical aperture stop ST not shown, a biconvex positive lens (third lens L3), and a negative meniscus convex on the image side. It consists of a lens (fourth lens L3). The second lens L2 has two aspheric surfaces. The third lens L3 and the fourth lens L4 are cemented lenses.

  The third lens group (Gr3) is composed of a negative meniscus lens (fifth lens L5) convex toward the image side. The fifth lens L5 has two aspheric surfaces.

  The fourth lens group (Gr4) is composed of a positive meniscus lens (sixth lens L6) convex toward the image side. The sixth lens L6 has two aspheric surfaces, and is, for example, a resin material lens.

  The optical diaphragm ST (not shown) is disposed in the second lens group (Gr2), and moves with the movement of the second lens group (Gr2). Then, on the image side of the fourth lens group (Gr4), the light receiving surface of the image sensor SR is arranged via a parallel plate FT as a filter. The parallel plate FT is a cover glass of various optical filters or an image sensor.

  In the variable magnification optical system 1E of Example 5, as shown in FIG. 10, during the magnification change from the wide angle end (W) through the intermediate point (M) to the telephoto end (T), the first lens group (Gr1) Is fixed, the second lens group (Gr2) is linearly moved in the direction approaching the object, and the optical diaphragm ST (not shown) moves together with the second lens group (Gr2), and the third lens group ( Gr3) is linearly moved in the direction approaching the object while being bent at the intermediate point (M), and the fourth lens group (Gr4) is fixed. Thus, in zooming from the wide-angle end (W) to the telephoto end (T), the first lens group (Gr1) and the second lens group (Gr2) move so that the distance between them becomes narrow.

  The construction data of each lens in the variable magnification optical system 1E of Example 5 is shown below.

Numerical Example 5
Unit mm
Surface data surface number r d nd νd
Object ∞ ∞
1 * -28.547 0.800 1.48749 70.45
2 * 3.005 Variable 3 * 3.946 1.455 1.68893 31.16
4 * (Aperture) 6.916 0.100
5 3.229 1.337 1.49700 81.61
6 -3.000 0.942 1.80518 25.46
7 -4.473 Variable 8 * -3.084 0.600 1.80518 25.46
9 * -53.885 Variable 10 * -9.667 2.424 1.60700 27.10
11 * -3.116 0.647
12 ∞ 0.3000 1.51680 64.20
13 ∞ 0.547
Image plane ∞
Aspherical data first surface K = 0.0000E + 00, A4 = -5.69180E-04, A6 = 1.16960E-04, A8 = -1.27640E-05, A10 = 4.87460E-07
Second surface K = 0.00000E + 00, A4 = -1.31070E-03, A6 = -1.36840E-04, A8 = -2.70270E-05, A10 = -3.42390E-06
3rd surface K = 0.00000E + 00, A4 = 3.92090E-03, A6 = 3.41370E-04, A8 = -7.15350E-06, A10 = 4.66360E-06
4th surface K = 0.00000E + 00, A4 = 9.35020E-03, A6 = 3.994040E-04, A8 = 4.94440E-04, A10 = -9.06130E-05
8th surface K = -1.00000E + 00, A4 = 1.86900E-02, A6 = -3.90470E-03, A8 = -2.63880E-03, A10 = 7.09920E-04
9th surface K = -1.00000E + 00, A4 = 3.01210E-02, A6 = -3.03800E-03, A8 = -9.00900E-04, A10 = 2.08980E-04
10th surface K = -1.00000E + 00, A4 = 9.94240E-04, A6 = -4.14290E-04, A8 = 4.97280E-05, A10 = -1.34980E-06
11th surface K = -1.00000E + 00, A4 = 4.29750E-03, A6 = -5.32660E-04, A8 = 1.88000E-05, A10 = 2.38550E-07
Various data zoom data Zoom ratio 2.72
Wide angle Medium telephoto focal length 4.437 7.743 12.061
F number 3.956 5.574 7.100
Angle of view 40.576 26.141 17.488
Image height 3.800 3.800 3.800
Total lens length 18.944 18.944 18.944
BF 1.391 1.391 1.391
d2 6.582 3.989 2.007
d7 1.655 1.879 2.649
d9 1.658 4.028 5.240
Zoom lens group data group Start surface End surface Focal length 1 1 2 -5.531
2 3 7 3.925
3 8 9 -4.084
4 10 11 6.646
FIG. 23, FIG. 24 and FIG. 25 show the spherical aberration (sinusoidal condition), astigmatism, distortion and lateral aberration in the variable magnification optical system 1E of Example 5 under the lens arrangement and configuration as described above. Respectively. FIG. 23 shows each aberration at the wide-angle end (W), FIG. 24 shows each aberration at the intermediate point (M), and FIG. 25 shows each aberration at the telephoto end (T).

  Table 1 shows numerical values when the above-described conditional expressions (1) to (15) are applied to the variable magnification optical systems 1A to 1E of Examples 1 to 5 listed above.

  As described above, the variable power optical systems 1A to 1E in Examples 1 to 5 satisfy the requirements according to the present invention, and as a result, the zoom ratio is about 2 to 3 times. Thus, the aberration is corrected well, and when mounted on a digital device, particularly when mounted on a portable terminal, downsizing can be sufficiently achieved, and the cost can be reduced.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

FIG. 2 is a lens cross-sectional view schematically showing the configuration for explaining the variable magnification optical system in the embodiment. It is a block diagram which shows the structure of the digital device in embodiment. It is an external appearance block diagram of the mobile phone with a camera which shows one Embodiment of a digital device. 3 is a cross-sectional view illustrating an arrangement of lens groups in a variable magnification optical system in Embodiment 1. FIG. 6 is a cross-sectional view illustrating an arrangement of lens groups in a variable magnification optical system in Example 2. FIG. 6 is a cross-sectional view illustrating an arrangement of lens groups in a variable magnification optical system in Example 3. FIG. 6 is a cross-sectional view illustrating an arrangement of lens groups in a variable magnification optical system in Example 4. FIG. 10 is a cross-sectional view illustrating an arrangement of lens groups in a variable magnification optical system according to Example 5. FIG. It is a figure which shows the mode of the movement of each lens group in zooming. It is a figure which shows the mode of the movement of each lens group in zooming. FIG. 4 is an aberration diagram of the lens unit at the wide angle end according to Example 1. FIG. 6 is an aberration diagram of a lens group at an intermediate point in Example 1. FIG. 4 is an aberration diagram of the lens unit at the telephoto end according to Example 1. FIG. 6 is an aberration diagram of the lens unit at the wide angle end according to Example 2. 6 is an aberration diagram of a lens group at an intermediate point in Example 2. FIG. 6 is an aberration diagram of a lens group at a telephoto end according to Example 2. FIG. 10 is an aberration diagram of a lens unit at a wide angle end according to Example 3. FIG. 10 is an aberration diagram of a lens group at an intermediate point in Example 3. FIG. 10 is an aberration diagram of a lens group at a telephoto end according to Example 3. FIG. FIG. 6 is an aberration diagram of a lens unit at a wide angle end according to Example 4. 10 is an aberration diagram of a lens group at an intermediate point in Example 4. FIG. 10 is an aberration diagram of a lens group at a telephoto end according to Example 4. FIG. 10 is an aberration diagram of a lens unit at a wide angle end according to Example 5. FIG. 10 is an aberration diagram of a lens group at an intermediate point in Example 5. FIG. 10 is an aberration diagram of a lens group at a telephoto end according to Example 5. FIG.

Explanation of symbols

AX Optical axis 1, 1A to 1E Variable magnification optical system 3 Digital device 5 Mobile phone 11, Gr1 first lens group 12, Gr2 second lens group 13, Gr3 third lens group 14, ST aperture 16, SR imaging device 21 apparatus

Claims (29)

In order from the object side to the image side, a first lens group having negative optical power, a second lens group having positive optical power, and a third lens group having negative optical power,
In zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group move so as to narrow the distance between each other,
The first lens group is composed of one negative lens,
The second lens group includes at least one positive lens and at least one negative lens,
A variable magnification optical system characterized by satisfying conditional expression (1) below.
| Hg2 | / Rg2> 0.15 (1)
However,
Hg2: the principal ray height (distance from the optical axis) of the light beam corresponding to the maximum image height on the most object side lens surface of the second lens group at the wide angle end
Rg2: Maximum effective radius of the lens surface closest to the object side in the second lens group Variable-power optical system according to claim 1, characterized in further including that the aperture stop disposed on the image side of the most object side lens surface of the second lens group. The zoom lens system according to claim 1 or 2, wherein the most object side lens of the second lens group has a positive optical power. 4. The variable power optical system according to claim 1, wherein the first lens group is fixed at the variable power. 5. 5. The zoom optical system according to claim 1, wherein at the wide-angle end, the following conditional expression (2) is satisfied: 5.
| Hg2 | / TLw> 0.01 (2)
However,
TLw: Distance on the optical axis from the surface vertex of the lens surface closest to the object side to the image plane at the wide-angle end when the object distance is infinite (however, the back focus is the air equivalent length) The variable magnification optical system according to any one of claims 1 to 5, wherein the negative lens of the first lens group satisfies the following conditional expressions (3) and (4).
N1 <1.65 (3)
v1> 50 (4)
However,
N1: Refractive index of the negative lens in the first lens group v1: Abbe number of the negative lens in the first lens group The variable magnification optical system according to any one of claims 1 to 6, wherein the second lens group satisfies the following conditional expression (5).
0.6 <f2 / fw <1.5 (5)
However,
f2: Composite focal length of the second lens group fw: Composite focal length of the entire optical system at the wide angle end The variable power optical system according to any one of claims 1 to 7, wherein the most image side lens of the variable power optical system satisfies the following conditional expressions (6) and (7).
1.5 <Ni (6)
vi <40 (7)
However,
Ni: Refractive index of the most image side lens in the variable magnification optical system vi: Abbe number of the most image side lens in the variable magnification optical system When focusing from an object at infinity to an object at a short distance, the third lens group moves,
The variable magnification optical system according to claim 1, wherein the following conditional expression (8) is satisfied.
0.8 <| f3 / fw | <1.5 (8)
However,
f3: Composite focal length of the third lens group fw: Composite focal length of the entire optical system at the wide angle end The variable magnification optical system according to claim 1, wherein the following conditional expression (9) is satisfied.
0.1 <Rg1 / TLw <0.3 (9)
However,
Rg1: Maximum effective radius of the most object side lens surface in the variable magnification optical system TLw: Distance on the optical axis from the surface vertex of the most object side lens surface to the image plane at the wide angle end when the object distance is infinite (however, The back focus is the air equivalent length) The zoom lens system according to any one of claims 1 to 10, wherein at the telephoto end, the following conditional expression (10) is satisfied.
T12 / (fw × ft) ^1/2 <0.2 (10)
However,
T12: Distance on the optical axis between the first lens group and the second lens group at the telephoto end fw: Composite focal length of all optical systems at the wide angle end ft: Composite focal length of all optical systems at the telephoto end The variable power optical system according to any one of claims 1 to 11, wherein the zoom lens system includes only the first to third lens groups. The zoom lens system according to claim 12, wherein the most object side lens of the second lens group satisfies the following conditional expression (11).
−0.4 <Rfg2 / Rrg2 <−0.2 (11)
However,
Rfg2: radius of curvature of the object side surface of the most object side lens in the second lens group Rrg2: radius of curvature of the image side surface of the most object side lens in the second lens group The zoom lens system according to claim 12 or 13, wherein the following conditional expression (12) is satisfied.
1.0 <Lb / fw <1.5 (12)
However,
Lb: Back focus at telephoto end (air equivalent length)
fw: Composite focal length of all optical systems at the wide-angle end The variable power optical system according to any one of claims 1 to 11, further comprising a fourth lens group having a positive optical power on an image side of the third lens group. 16. The variable magnification optical system according to claim 15, comprising only the first to fourth lens groups. The zoom lens system according to claim 15 or 16, wherein the most object side lens of the second lens group satisfies the following conditional expression (13).
0.3 <Rfg2 / Rrg2 <0.6 (13)
However,
Rfg2: radius of curvature of the object side surface of the most object side lens in the second lens group Rrg2: radius of curvature of the image side surface of the most object side lens in the second lens group The zoom lens system according to any one of claims 15 to 17, wherein the following conditional expression (14) is satisfied.
0.2 <Lb / fw <0.4 (14)
However,
Lb: Back focus at telephoto end (air equivalent length)
fw: Composite focal length of all optical systems at the wide-angle end The variable aperture optical system according to claim 2, wherein the aperture stop is disposed on the image side with respect to the most image side lens surface of the second lens group. The zoom lens system according to any one of claims 1 to 19, wherein there are only two movable lens groups in the zooming. 21. The variable magnification optical system according to claim 1, wherein the third lens group includes at least one aspherical surface. The variable magnification optical system according to any one of claims 1 to 21, further comprising at least one lens made of a resin material. The at least one lens made of a resin material is disposed in the third lens group or closer to the image side than the third lens group. The variable power optical system described. 24. The second lens group is configured to move toward the object side during the zooming from the wide-angle end to the telephoto end, and includes three or less lenses. The zoom optical system according to any one of the above. The variable magnification optical system according to any one of claims 1 to 24, wherein the second lens group includes a cemented lens. The variable power optical system according to any one of claims 1 to 25, wherein the third lens group includes two or more lenses. A variable magnification optical system according to any one of claims 1 to 26;
An image sensor that converts an optical image into an electrical signal,
An image pickup apparatus, wherein the variable magnification optical system is capable of forming an optical image of an object on a light receiving surface of the image pickup device. An imaging device according to claim 27;
A controller that causes the imaging device to perform at least one of still image shooting and moving image shooting of a subject;
A digital apparatus, wherein a variable magnification optical system of the imaging apparatus is assembled so that an optical image of the subject can be formed on a light receiving surface of the imaging element. The digital device according to claim 28, comprising a mobile terminal.

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