WO2012176470A1 - Zoom lens and imaging device - Google Patents

Zoom lens and imaging device Download PDF

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Publication number
WO2012176470A1
WO2012176470A1 PCT/JP2012/004058 JP2012004058W WO2012176470A1 WO 2012176470 A1 WO2012176470 A1 WO 2012176470A1 JP 2012004058 W JP2012004058 W JP 2012004058W WO 2012176470 A1 WO2012176470 A1 WO 2012176470A1
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Prior art keywords
lens
lens group
zoom
lenses
conditional expression
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PCT/JP2012/004058
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French (fr)
Japanese (ja)
Inventor
大樹 河村
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富士フイルム株式会社
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Publication of WO2012176470A1 publication Critical patent/WO2012176470A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B15/00—Optical objectives with means for varying the magnification
    • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/16—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group
    • G02B15/177—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a negative front lens or group of lenses

Definitions

  • the present invention relates to a zoom lens and an imaging apparatus, and more particularly, to a zoom lens that can be suitably used for a small camera or a portable terminal apparatus, and an imaging apparatus including such a zoom lens.
  • Patent Document 1 shows examples thereof.
  • Patent Documents 2 and 3 as an example of a low-cost zoom lens in which a zoom ratio is about 3 times and a simpler two-group type is adopted, there are two first lens groups and two second lens groups.
  • Patent Document 4 shows a zoom lens composed of a total of four lenses, two first lens groups and two second lens groups.
  • Patent Documents 5 and 6 disclose a zoom lens using a plastic lens, or a zoom lens designed on the assumption that the lens is composed of a plastic lens.
  • Patent Document 5 shows an example in which one of the three lenses constituting the first lens group is a plastic lens.
  • Patent Document 6 shows an example in which all lenses are made of plastic lenses.
  • the zoom lens disclosed in Patent Document 4 is configured with an extremely small number of lenses.
  • the number of lenses is small as described above, cost reduction cannot be realized simply. For example, if the number of lenses is small, the power of each lens increases, and the tolerance of manufacturing errors and assembly errors decreases, and the processing difficulty of lenses increases, resulting in lower production costs. There is also the possibility of becoming high.
  • the power of the second lens group as shown in Patent Document 4 is distributed to two lenses.
  • the configuration of the second group shown in Documents 2 and 3 is considered preferable.
  • the power that one positive lens arranged in the second group bears is reduced, so that the lens can be made of plastic.
  • the lenses arranged in the first lens group are made of a high refractive index material, leaving room for further cost reduction.
  • Examples of zoom lenses using plastic lenses include those described in Patent Documents 5 and 6 as described above, and those first lens groups are zoom lenses disclosed in Patent Documents 2 to 4.
  • the number of lenses is one more than that of the first lens group of the lens.
  • the power is dispersed by dividing one lens having high power into two lenses, and a lens having a power reduced to a certain extent is applied. There is also. However, if such a configuration is adopted, the retractable length becomes large.
  • Patent Document 6 shows an example in which all lenses are made of plastic lenses, but in that case, the zoom ratio is only about twice.
  • the present invention has been made in view of the circumstances described above, and achieves cost reduction by adopting a plastic lens while securing a zoom ratio of about 3 to 4 times with a small number of lenses, and each lens.
  • An object of the present invention is to provide a two-group zoom lens that can realize good optical performance by optimally setting the power of the zoom lens.
  • the first zoom lens according to the present invention comprises: The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming.
  • zoom lenses where Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses,
  • M2 the amount of movement of the second lens unit when zooming from the wide-angle end to the telephoto end
  • ft the focal length of the entire system at the telephoto end
  • “consisting essentially of the first lens group and the second lens group” means an optical element other than the lens group, such as a lens having substantially no power, a diaphragm, a cover glass, etc.
  • a mechanism portion such as a lens flange, a lens barrel, an image sensor, a camera shake correction mechanism, or the like is included is also included.
  • the first lens group has a negative refractive power substantially in order from the object side and the positive refractive power. The same applies to the description of “consisting of two of the second lenses having”.
  • Each lens group in the zoom lens of the present invention may be composed of three or more plastic lenses.
  • a cemented lens may be used as a lens constituting each lens group. However, if the cemented lens is configured by bonding of n sheets, it is counted as n lenses.
  • the description of “the zoom lens of the present invention” or “the zoom lens of the present invention” refers to both the first zoom lens according to the present invention and the second zoom lens described later unless otherwise specified. Shall be pointed to.
  • the surface shape of the lens and the sign of the refractive power are considered in the paraxial region when an aspheric surface is included.
  • the focal length of the entire system at the telephoto end is ft and the focal length of the first lens group is f1
  • the second zoom lens according to the present invention includes: The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming.
  • zoom lenses where Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses, When the focal length of the entire system at the telephoto end is ft and the focal length of the first lens unit is f1, the following conditional expression 1.5 ⁇
  • the first lens group has at least one positive lens and the Abbe number of the positive lens with respect to the d-line is ⁇ d1p
  • the second lens group has at least one negative lens
  • the Abbe number of the negative lens with respect to the d-line is ⁇ d2n
  • the first lens group is composed of two lenses, a first lens having a negative refractive power and a second lens having a positive refractive power, in order from the object side.
  • conditional expressions (3) to (6) may satisfy a part (one or more) of them.
  • the more desirable ranges of the conditions indicated by the conditional expressions (3), (4), (5) and (6) are as follows.
  • the entire second lens group or a part of the lenses arranged in the second lens group is moved along the optical axis when focusing from infinity to a short distance. It is preferable. More specifically, when the second lens group is composed of a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power in order from the object side, It is preferable that only the fifth lens be moved along the optical axis.
  • the zoom lens of the present invention when the first lens group has at least one negative lens, and the refractive index and Abbe number of the negative lens with respect to the d-line are nd1n and ⁇ d1n, respectively, the following conditional expression 1 .48 ⁇ nd1n ⁇ 1.56 (7) 50 ⁇ d1n> 60 (8) Is preferably satisfied.
  • the second lens group has at least one positive lens
  • the refractive index and Abbe number for the d-line of the positive lens are nd2p and ⁇ d2p, respectively, 48 ⁇ nd2p ⁇ 1.56 (9) 50 ⁇ d2p ⁇ 60 (10) Is preferably satisfied.
  • the first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power.
  • the lenses satisfy the following conditions: 1.48 ⁇ nd11 ⁇ 1.61 (11) ) 50 ⁇ d11 (12), more preferably 52 ⁇ d11 (12 ′) 1.56 ⁇ nd12 ⁇ 1.66 (13) ⁇ d12 ⁇ 33 (14), more preferably ⁇ d12 ⁇ 29 (14 ′) It is desirable to be formed from a plastic material that satisfies
  • the second lens group includes, in order from the object side, a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power.
  • the third lens has a refractive index with respect to the d-line and Abbe numbers of nd21 and ⁇ d21, respectively
  • the fourth lens has a refractive index with respect to the d-line and Abbe numbers of nd22 and ⁇ d22, respectively.
  • these lenses satisfy the following conditions: 1.48 ⁇ nd21 ⁇ 1.61 (15) 50 ⁇ d21 (16), more preferably 52 ⁇ d21 (16 ′) 1.56 ⁇ nd22 ⁇ 1.68 (17) ⁇ d22 ⁇ 33 (18), more preferably ⁇ d22 ⁇ 29 (18 ′) 1.48 ⁇ nd23 ⁇ 1.61 (19) 50 ⁇ d23 (20), more preferably 52 ⁇ d23 (20 ′) It is desirable to be formed from a plastic material that satisfies
  • an imaging apparatus is characterized by including the first or second zoom lens according to the present invention described above.
  • the first zoom lens according to the present invention substantially includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power.
  • each of the first lens group and the second lens group is composed of at least two lenses by applying a plastic lens, on which the above-described lens is arranged. Since it is assumed that the conditional expression (1) is satisfied, a plastic lens is used to achieve cost reduction, and each lens is secured while maintaining a zoom ratio of about 3 to 4 times with a small number of lenses. Optimum power can be set to achieve good optical performance.
  • Conditional expression (1) defines the relationship between the amount of movement of the second lens unit and the focal length of the entire system at the telephoto end. If the lower limit of the conditional expression is not reached, it is difficult to increase the zoom ratio. Become. In this case, the power of the second lens group must be increased, which is not preferable because the tolerance for manufacturing errors and assembly errors is reduced. Further, in that case, the power of the plastic lens becomes strong, and the change in optical performance and characteristics due to temperature increases, which is not preferable. On the other hand, if the upper limit value of the conditional expression is exceeded, the amount of movement of the second lens group increases and the lens system becomes larger, which is not preferable. When the conditional expression (1) is satisfied, the above-described problems can be prevented and the above effect can be obtained.
  • this conditional expression (2) defines the relationship between the focal length of the entire system at the telephoto end and the focal length of the first lens group. This is not preferable because the system becomes large.
  • the upper limit value is exceeded, it becomes difficult to correct curvature of field mainly near the wide-angle end. Further, the power of the plastic lens becomes strong, and the optical performance and characteristics change with temperature, which is not preferable.
  • the conditional expression (2) is satisfied, the above problems can be prevented, and the above effect can be made more remarkable.
  • the second zoom lens according to the present invention substantially comprises, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power.
  • each of the first lens group and the second lens group is composed of at least two lenses by applying a plastic lens. Since the conditional expression (2) is satisfied, a plastic lens is used to achieve a reduction in cost, and a zoom ratio of about 3 to 4 times is secured with a small number of lenses. By setting the lens power optimally, there is an effect that good optical performance can be realized.
  • satisfying the conditional expression (2) causes the problem as described above, that is, the lens system becomes large, and it becomes difficult to correct the curvature of field near the wide-angle end.
  • the above effect can be obtained by preventing problems such as a large change in optical performance and characteristics.
  • the conditional expression (1) when the conditional expression (1) is satisfied, the same effect as that when the conditional expression (2) is particularly satisfied in the first zoom lens is obtained. be able to.
  • Conditional expression (3) prescribes the Abbe number of at least one positive lens arranged in the first lens group, and it is not preferable to deviate from the conditional expression because chromatic aberration of magnification becomes particularly large. When the conditional expression (3) is satisfied, the above problem can be prevented.
  • Conditional expression (4) defines the Abbe number of at least one negative lens arranged in the second lens group, and if it falls outside the range of the conditional expression, axial chromatic aberration increases, which is not preferable. . When the conditional expression (4) is satisfied, the above problem can be prevented.
  • Conditional expression (5) defines the relationship between the distance between the first lens and the second lens arranged in the first lens group and the focal length of the entire system at the wide-angle end. Although it is advantageous for downsizing, it is not preferable because correction of spherical aberration becomes difficult. On the other hand, if the upper limit value is exceeded, the entire first lens group will be enlarged, which is not preferable. When the conditional expression (5) is satisfied, the above problem can be prevented.
  • Conditional expression (6) defines the relationship between the focal lengths at the wide-angle end and the telephoto end, that is, the zoom ratio, and if it is below the lower limit value, the significance as a zoom lens is reduced. On the other hand, if the upper limit is exceeded, the lens system becomes large. In addition, this zoom type is not preferable because the brightness decreases excessively at the telephoto end. Also, if it is attempted to secure a certain level of brightness at the telephoto end, the burden on the second lens group becomes large, and aberration correction with a small number of lenses becomes difficult. When the conditional expression (6) is satisfied, the above problem can be prevented.
  • conditional expressions (3), (4), (5) and (6) described above are particularly the conditional expressions (3 ′), (4 ′) and (5), respectively, within the range defined by each conditional expression. If ') and (6') are satisfied, it becomes more prominent.
  • the refractive index nd1n of the negative lens arranged in the first lens group is equal to or lower than the lower limit value of the conditional expression (7), the curvature of the lens (approximate curvature) becomes large and it is difficult to correct curvature of field and distortion. become.
  • the value exceeds the upper limit it is difficult to balance astigmatism and lateral chromatic aberration correction, which is not preferable.
  • the Abbe number ⁇ d1n of the negative lens arranged in the first lens group is out of the range of the conditional expression (8), it is difficult to correct the lateral chromatic aberration particularly near the wide-angle end, but the conditional expression (8) When satisfied, this problem can be prevented.
  • the refractive index nd2p of the positive lens arranged in the second lens group is equal to or lower than the lower limit value of the conditional expression (9), the curvature of the lens (approximate curvature) increases and the amount of aberration generated increases.
  • the value exceeds the upper limit astigmatism increases, which is not preferable.
  • the first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power, and the conditional expression (11 ) To (14), the following effects can be obtained.
  • Conditional expression (11) and conditional expression (13) define the refractive index of the first lens and the refractive index of the second lens, respectively, and the occurrence of aberration increases when the conditional expression is below the lower limit of these conditional expressions.
  • the curvature of the lens (approximate curvature) increases and the first lens group becomes thick.
  • the two lenses arranged in the first lens group are to be composed of plastic lenses for the purpose of cost reduction and weight reduction, they are composed of a material that exceeds the upper limit value of the conditional expressions. Then, it becomes difficult to balance the correction of astigmatism and lateral chromatic aberration, which is not preferable.
  • the conditional expression (11) or (13) is satisfied, the above problems can be prevented.
  • Conditional expression (12) and conditional expression (14) define the Abbe number of the first lens and the Abbe number of the second lens, respectively, and the first lens and the second lens are out of the range of these conditional expressions. And the Abbe number difference becomes small, and correction of chromatic aberration becomes difficult. If the range of the conditional expression (12) or (14) is exceeded, the Abbe number of the second lens is defined by the other lens (conditional expression (14)) arranged in the first lens group in order to correct chromatic aberration. In this case, the first lens is the “other lens”, and when the Abbe number of the first lens is defined by the conditional expression (12), the power of the second lens is the “other lens”. In particular, it is difficult to correct curvature of field and distortion at the wide-angle end, which is not preferable. When the conditional expression (12) or (14) is satisfied, the above problems can be prevented.
  • conditional expressions (12 ') and (14') are satisfied, respectively, within the ranges of conditional expressions (12) and (14).
  • the second lens group includes, in order from the object side, a third lens having a positive refractive power, a fourth lens having a negative refractive power, and a fifth lens having a positive refractive power.
  • conditional expressions (16 ′), (18 ′), and (20 ′) are satisfied, respectively, within the ranges of conditional expressions (16), (18), and (20). , Become more prominent.
  • the zoom lens of the present invention in particular, when focusing from infinity to a short distance, the entire second lens group or a part of the lenses arranged in the second lens group is moved along the optical axis. If so, the following effects can be obtained. That is, when the configuration in which the entire first lens group is extended and focused is adopted, the effective diameter of the first lens group becomes large or the lens having a large outer diameter needs to be moved. Alternatively, when a part of the lenses arranged in the second lens group is moved, such a problem can be avoided.
  • the second lens group is composed of a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power in order from the object side. This is more noticeable when only the lens is moved along the optical axis.
  • the image pickup apparatus according to the present invention includes the zoom lens according to the present invention that achieves the above-described effects, it is possible to achieve cost reduction while providing good optical performance.
  • Sectional view showing the lens configuration of the zoom lens according to Example 1 of the present invention Sectional drawing which shows the lens structure of the zoom lens concerning Example 2 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 3 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 4 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 5 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 6 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 7 of this invention.
  • (A) to (H) are aberration diagrams of the zoom lens of Example 1 of the present invention.
  • (A) to (H) are aberration diagrams of the zoom lens according to Example 2 of the present invention.
  • FIG. 1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention.
  • FIG. 1 is a cross-sectional view illustrating a configuration example of a zoom lens according to an embodiment of the present invention, and corresponds to a zoom lens of Example 1 described later.
  • 2 to 7 are cross-sectional views showing other configuration examples according to the embodiment of the present invention, which respectively correspond to zoom lenses of Examples 2 to 7 described later.
  • the basic configuration of the example shown in FIGS. 1 to 7 is the same as that of the embodiment shown in FIGS. 2 and 7 except that the second lens group G2 includes two lenses. Therefore, the zoom lens according to the embodiment of the present invention will be described mainly with reference to FIG.
  • FIG. 1 the left side is the object side, the right side is the image side, (A) is the infinitely focused state and the optical system arrangement at the wide angle end (shortest focal length state), and (B) is the infinitely focused state. And the arrangement of the optical system at the telephoto end (longest focal length state). The same applies to FIGS. 2 to 7 described later.
  • the zoom lens according to the embodiment of the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power arranged as a lens group.
  • the second lens group G2 includes an aperture stop St.
  • the aperture stop St shown here does not necessarily indicate the size or shape, but indicates the position on the optical axis Z.
  • FIG. 1 shows an example in which a parallel plate-shaped optical member PP is disposed between the second lens group G2 and the image plane Sim.
  • various filters such as a cover glass, an infrared cut filter, and a low-pass filter are arranged between the optical system and the image plane Sim according to the configuration of the camera on which the lens is mounted. It is preferable.
  • the optical member PP assumes such cover glass and various filters.
  • some image pickup apparatuses employ a 3CCD system that uses a CCD for each color in order to improve image quality.
  • a color separation optical system such as a color separation prism is used. It is inserted between the lens system and the image plane Sim. In that case, a color separation optical system may be arranged at the position of the optical member PP.
  • the first lens group G1 moves so as to draw a convex locus on the image plane Sim side, and the second lens group G2 monotonously moves toward the object side.
  • the aperture stop St is configured to move integrally with the second lens group G2.
  • FIG. 1 the movement trajectories of the first lens group G1 and the second lens group G2 when zooming from the wide-angle end to the telephoto end are schematically shown by solid line arrows between (A) and (B). Is shown.
  • the first lens group G1 includes a first lens L11 having a negative refractive power and a second lens L12 having a positive refractive power, which are arranged in order from the object side.
  • the first lens L11 can be a biconcave lens
  • the second lens L12 can be a positive meniscus lens.
  • the first lens group G1 is composed of at least two lenses.
  • the first lens group G1 is composed of the two lenses L11 and L12 as described above, and Both of them are plastic lenses.
  • the second lens group G2 is composed of at least two lenses, but the second lens group G2 in the structure of FIG. 1 has a positive refractive power arranged in order from the object side.
  • the third lens L21 includes a fourth lens L22 having a negative refractive power, and a fifth lens L23 having a positive refractive power.
  • the third lens L21 can be a biconvex lens
  • the fourth lens L22 can be a biconcave lens
  • the fifth lens L23 can be a positive meniscus lens. All the lenses L21, L22, and L23 of the second lens group G2 are also plastic lenses.
  • the first lens group G1 is composed of the two lenses L11 and L12 and the second lens group G2 is composed of the three lenses L21, L22 and L23, and these lenses are all plastic lenses. Thus, cost reduction can be achieved.
  • the second lens group G2 includes two lenses, that is, the third lens L21 and the fourth lens L22.
  • the above effect can also be obtained with this configuration.
  • the second lens group G2 has one negative lens (fourth lens L22), and the Abbe number of the negative lens with respect to the d-line is ⁇ d2n, the following conditional expression ⁇ d2n ⁇ 29. (4) Is satisfied.
  • the first lens group G1 is composed of two lenses, a first lens L11 having a negative refractive power and a second lens L12 having a positive refractive power, in order from the object side.
  • the air interval on the optical axis Z of the two lenses is d2
  • the focal length of the entire system at the wide angle end is fw
  • conditional expressions (3) to (6) need not all be satisfied, and some of them may be satisfied.
  • the more desirable ranges of the conditions shown in the conditional expressions (3), (4), (5) and (6) are as follows: ⁇ d1p ⁇ 26 (3 ′) ⁇ d2n ⁇ 26 (4 ′) 0.31 ⁇ d2 / fw ⁇ 0.60 (5 ′) 2.3 ⁇ ft / fw ⁇ 5.0 (6 ′) In this embodiment, all of these conditional expressions are also satisfied.
  • the zoom lens has a configuration in which the entire second lens group G2 is moved along the optical axis Z during focusing from infinity to a short distance. It should be noted that some lenses arranged in the second lens group G2 may be moved along the optical axis Z. More specifically, a configuration in which only the fifth lens L23 is moved along the optical axis Z can be employed.
  • the first lens group G1 has one negative lens (first lens L11) and the refractive index and Abbe number of the negative lens with respect to the d-line are nd1n and ⁇ d1n, respectively, Conditional expression of 1.48 ⁇ nd1n ⁇ 1.56 (7) 50 ⁇ d1n> 60 (8) Is satisfied.
  • the second lens group G2 has two positive lenses (third lens L21 and fifth lens L23), and the refractive index and Abbe number of the positive lens with respect to the d-line are nd2p and ⁇ d2p, respectively. Then, the following conditional expression 1.48 ⁇ nd2p ⁇ 1.56 (9) 50 ⁇ d2p ⁇ 60 (10) Is satisfied.
  • the first lens group G1 is composed of a first lens L11 having negative refractive power and a second lens L12 having positive refractive power in order from the object side.
  • the refractive index and Abbe number for nd are nd11 and ⁇ d11, respectively
  • the refractive index and Abbe number for the d-line of the second lens L12 are nd12 and ⁇ d12, respectively.
  • conditional expressions (12) and (14) The range of more desirable values within the conditions defined by the conditional expressions (12) and (14) is 52 ⁇ d11 (12 ′) ⁇ d12 ⁇ 29 (14 ′) However, in this embodiment, these conditional expressions (12 ′) and (14 ′) are also satisfied.
  • the second lens group G2 in order from the object side, a third lens L21 having a positive refractive power, a fourth lens L22 having a negative refractive power, and a fifth lens L23 having a positive refractive power.
  • the refractive index and Abbe number of the third lens L21 for the d-line are nd21 and ⁇ d21, respectively, and the refractive index and Abbe number of the fourth lens L22 for the d-line are nd22 and ⁇ d22, respectively, and d of the fifth lens L23.
  • these lenses have the following conditions: 1.48 ⁇ nd21 ⁇ 1.61 (15) 50 ⁇ d21 (16) 1.56 ⁇ nd22 ⁇ 1.68 (17) ⁇ d22 ⁇ 33 (18) 1.48 ⁇ nd23 ⁇ 1.61 (19) 50 ⁇ d23 (20) It is formed from a plastic material that satisfies the requirements.
  • the range of more desirable values within the conditions defined by the conditional expressions (16), (18) and (20) is 52 ⁇ d21 (16 ′) below. ⁇ d22 ⁇ 29 (18 ′) 52 ⁇ d23 (20 ′)
  • these conditional expressions (16 ′), (18 ′), and (20 ′) are also satisfied.
  • Conditional expression (1) defines the relationship between the amount of movement of the second lens group G2 and the focal length of the entire system at the telephoto end.
  • the conditional expression (1) is below the lower limit of the conditional expression, the zoom ratio can be increased. It becomes difficult. In this case, it is not preferable because the power of the second lens group G2 must be increased, and an allowable amount of manufacturing error and assembly error is reduced. Further, in that case, the power of the plastic lens becomes strong, and the change in optical performance and characteristics due to temperature increases, which is not preferable.
  • the upper limit of the conditional expression is exceeded, the amount of movement of the second lens group G2 becomes large, and the lens system becomes large, which is not preferable.
  • the conditional expression (1) is satisfied, the above-mentioned problems are prevented, and the power of each lens is set optimally while securing a zoom ratio of about 3 to 4 times with a small number of lenses. With this, good optical performance can be realized.
  • Conditional expression (2) defines the relationship between the focal length of the entire system at the telephoto end and the focal length of the first lens group G1, and when it becomes less than the lower limit, the amount of movement during zooming increases, and the lens system Is unfavorable because it increases in size.
  • the upper limit value is exceeded, it becomes difficult to correct curvature of field mainly near the wide-angle end. Further, the power of the plastic lens becomes strong, and the optical performance and characteristics change with temperature, which is not preferable.
  • the conditional expression (2) is satisfied, the above-described problems can be prevented, so that the above-described effect, that is, good optical performance can be obtained while securing a zoom ratio of about 3 to 4 times with a small number of lenses. The effect of being realizable can be made more remarkable.
  • Conditional expression (3) defines the Abbe number of the positive lens (second lens L12) disposed in the first lens group G1, and if the range of the conditional expression is outside the range, the chromatic aberration of magnification becomes particularly large. It is not preferable. When the conditional expression (3) is satisfied, the above problem can be prevented.
  • Conditional expression (4) prescribes the Abbe number of the negative lens (fourth lens L22) disposed in the second lens group G2, and the axial chromatic aberration becomes particularly large if the conditional expression is outside the range. It is not preferable. When the conditional expression (4) is satisfied, the above problem can be prevented.
  • Conditional expression (5) defines the relationship between the distance between the first lens L11 and the second lens L12 arranged in the first lens group G1 and the focal length of the entire system at the wide-angle end, and is below the lower limit value thereof. Then, it is advantageous for downsizing, but it is not preferable because correction of spherical aberration becomes difficult. On the other hand, if the upper limit value is exceeded, the entire first lens group G1 becomes large, which is not preferable. When the conditional expression (5) is satisfied, the above problem can be prevented.
  • Conditional expression (6) defines the relationship between the focal lengths at the wide-angle end and the telephoto end, that is, the zoom ratio, and if it is below the lower limit value, the significance as a zoom lens is reduced. On the other hand, if the upper limit is exceeded, the lens system becomes large. In addition, this zoom type is not preferable because the brightness decreases excessively at the telephoto end. Further, if it is attempted to secure a certain level of brightness at the telephoto end, the burden on the second lens group G2 increases, and it becomes difficult to correct aberrations with a small number of lenses. When the conditional expression (6) is satisfied, the above problem can be prevented.
  • conditional expressions (3 ′), (4 ′), and (5 ′) are particularly preferable within the ranges defined by the conditional expressions (3), (4), (5), and (6) described above. ) And (6 ′) are satisfied, the above effect becomes more remarkable.
  • the refractive index nd1n of the negative lens (first lens L11) arranged in the first lens group G1 is equal to or lower than the lower limit value of the conditional expression (7), the curvature of the lens (approximate curvature) increases and the curvature of field is increased. And it becomes difficult to correct distortion. On the other hand, if the value exceeds the upper limit, it is difficult to balance astigmatism and lateral chromatic aberration correction, which is not preferable. Since this zoom lens satisfies the conditional expression (7), the above-mentioned problem can be prevented.
  • the Abbe number ⁇ d1n of the negative lens (first lens L11) arranged in the first lens group G1 is out of the range of the conditional expression (8), it is difficult to correct lateral chromatic aberration particularly near the wide-angle end. Since this zoom lens satisfies the conditional expression (8), this problem can be prevented.
  • the lens curvature (approximate curvature) becomes large. As a result, the amount of aberration generated becomes large.
  • the value exceeds the upper limit astigmatism increases, which is not preferable. Since this zoom lens satisfies the conditional expression (9), the above-described problem can be prevented.
  • the Abbe number ⁇ d2p of the positive lenses (the third lens L21 and the fifth lens L23) arranged in the second lens group G2 is out of the range of the conditional expression (10), it is difficult to correct axial chromatic aberration. Since this zoom lens satisfies the conditional expression (10), this problem can be prevented.
  • the first lens group G1 includes, in order from the object side, the first lens L11 having a negative refractive power and the second lens L12 having a positive refractive power, and then the conditional expression (11 ) To (14) are satisfied, the following effects can be obtained. That is, conditional expression (11) and conditional expression (13) define the refractive index of the first lens L11 and the refractive index of the second lens L12, respectively. Is increased, the curvature of the lens (approximate curvature) is increased, and the first lens group G1 is thickened.
  • the two lenses L11 and L12 arranged in the first lens group G1 are made of plastic lenses for the purpose of cost reduction and weight reduction, a material that exceeds the upper limit value of these conditional expressions. This is not preferable because it is difficult to balance correction of astigmatism and lateral chromatic aberration. Since this zoom lens satisfies the conditional expressions (11) and (13), the above problems can be prevented.
  • Conditional expression (12) and conditional expression (14) define the Abbe number of the first lens L11 and the Abbe number of the second lens L12, respectively. The difference in Abbe number from the second lens L12 becomes small, and correction of chromatic aberration becomes difficult. If the range of the conditional expression (12) or (14) is exceeded, the Abbe number of the second lens L12 in the other lens (conditional expression (14)) arranged in the first lens group G1 is corrected for chromatic aberration correction.
  • the first lens L11 is this “other lens” when it is defined
  • the second lens L12 is this “other lens” when the Abbe number of the first lens L11 is defined by the conditional expression (12)) Is also not preferable because it is difficult to correct curvature of field and distortion at the wide-angle end. Since this zoom lens satisfies the conditional expressions (12) and (14), the above problems can be prevented.
  • conditional expressions (12 ′) and (14 ′) are satisfied particularly within the ranges of conditional expressions (12) and (14), respectively. Become.
  • the zoom lens of the present invention in particular, the second lens group G2, in order from the object side, a third lens L21 having a positive refractive power, a fourth lens L22 having a negative refractive power, and a fifth lens having a positive refractive power.
  • a third lens L21 having a positive refractive power in order from the object side, a fourth lens L22 having a negative refractive power, and a fifth lens having a positive refractive power.
  • conditional expressions (16 ′), (18 ′), and (20 ′) are satisfied particularly within the ranges of the conditional expressions (16), (18), and (20). Becomes more prominent.
  • the zoom lens has a configuration in which the entire second lens group G2 is moved along the optical axis Z during focusing from infinity to a short distance, so that the following effects can be obtained. That is, when the configuration in which the entire first lens group G1 is extended and focused is adopted, the effective diameter of the first lens group G1 or the lens having a large outer diameter needs to be moved. Such a problem can be avoided when moving the entire group G2.
  • FIG. 1 shows an example in which the optical member PP is disposed between the lens system and the imaging plane, but instead of disposing a low-pass filter, various filters that cut a specific wavelength range, etc. These various filters may be disposed between the lenses, or a coating having the same action as the various filters may be applied to the lens surface of any lens.
  • FIGS. 1 to 7 Lens sectional views of the zoom lenses of Examples 1 to 7 are shown in FIGS. 1 to 7, respectively.
  • Table 1 shows basic lens data of the zoom lens of Example 1
  • Table 2 shows data relating to zooming
  • Table 3 shows aspherical data
  • Tables 4 to 21 show basic lens data, zoom-related data, and aspherical data of the zoom lenses of Examples 2 to 7, respectively.
  • the meaning of the symbols in the table will be described using the example 1 as an example, but the same applies to the examples 2 to 7.
  • the i-th (i 1, 2, 3,...) That sequentially increases toward the image side with the object-side surface of the most object-side component as the first.
  • the surface number is indicated
  • the Ri column indicates the radius of curvature of the i-th surface
  • the Di column indicates the surface interval on the optical axis Z between the i-th surface and the i + 1-th surface.
  • the sign of the radius of curvature is positive when the surface shape is convex on the object side and negative when the surface shape is convex on the image side.
  • the basic lens data also includes the aperture stop St, and ⁇ (aperture stop) is described in the column of the radius of curvature of the surface corresponding to the aperture stop St.
  • D4 and D11 in the basic lens data in Table 1 are surface intervals that change during zooming.
  • D4 is the distance between the first lens group G1 and the second lens group G2
  • D11 is the distance between the second lens group G2 and the optical member PP.
  • D9 is used instead of D11.
  • the zoom-related data in Table 2 includes the focal length (f), F value (Fno.), Total angle of view (2 ⁇ ), and the distance between each surface that changes during zooming at the wide-angle end and the telephoto end. Is shown.
  • the surface number of the aspheric surface is marked with *, and the paraxial radius of curvature is shown as the radius of curvature of the aspheric surface.
  • the aspheric data in Table 3 shows the surface number of the aspheric surface and the aspheric coefficient for each aspheric surface.
  • the numerical value “E ⁇ n” (n: integer) of the aspherical data in Table 3 means “ ⁇ 10 ⁇ n ”.
  • Zd C ⁇ h 2 / ⁇ 1+ (1 ⁇ KA ⁇ C 2 ⁇ h 2 ) 1/2 ⁇ + ⁇ RAm ⁇ h m
  • Zd Depth of aspheric surface (length of a perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis where the aspherical vertex contacts)
  • h Height (distance from the optical axis to the lens surface)
  • C Reciprocal number of paraxial radius of curvature KA
  • values rounded to a predetermined digit are shown.
  • surface described below although the degree is used as a unit of angle and mm is used as a unit of length, an optical system can be used by proportional expansion or proportional reduction. Thus, other suitable units can be used.
  • Table 22 shows values corresponding to the conditional expressions (1) to (20) of the zoom lenses of Examples 1 to 7.
  • the values in Table 22 relate to the d line.
  • FIGS. 8A to 8D show spherical aberration, astigmatism, distortion (distortion aberration) and lateral chromatic aberration (chromatic aberration of magnification) at the wide-angle end of the zoom lens of Example 1
  • FIGS. 8E to 8H show spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration (chromatic aberration of magnification) at the edges, respectively.
  • Each aberration diagram is based on the d-line (wavelength 587.6 nm), but the spherical aberration diagram also shows aberrations relating to wavelengths 460.0 nm and 615.0 nm, and the lateral chromatic aberration diagram shows wavelengths 460.0 nm and 615.0 nm. The aberration about is shown. In the astigmatism diagram, the sagittal direction is indicated by a solid line, and the tangential direction is indicated by a dotted line. Fno. Of spherical aberration diagram. Means F value, and ⁇ in other aberration diagrams means half angle of view.
  • FIGS. 9A to 9H the aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Example 2 are shown in FIGS. 9A to 9H, and the aberration diagrams of Examples 3 to 7 are respectively the same in the same manner. It is shown in FIGS.
  • FIG. 15 shows a schematic configuration diagram of an imaging apparatus 10 using the zoom lens 1 of the embodiment of the present invention as an example of the imaging apparatus of the embodiment of the present invention.
  • the imaging device include a surveillance camera, a video camera, and an electronic still camera.
  • An image pickup apparatus 10 shown in FIG. 15 is arranged on the zoom lens 1, the image side of the zoom lens 1, an image pickup device 2 that picks up an image of a subject imaged by the zoom lens 1, and an output from the image pickup device 2.
  • a signal processing unit 4 that performs signal processing, a zooming control unit 5 for zooming the zoom lens 1, and a focus control unit 6 for performing focus adjustment are provided.
  • a filter or the like may be appropriately disposed between the zoom lens 1 and the image sensor 2.
  • the zoom lens 1 has a negative refractive power, a first lens group G1 that moves so as to draw a convex locus on the image plane side when zooming from the wide angle end to the telephoto end, and a positive refractive power. And a second lens group G2 that moves monotonically toward the object side when zooming from the wide-angle end to the telephoto end, and an aperture stop St that is configured to move integrally with the second lens group G2. is doing.
  • FIG. 15 schematically shows each lens group.
  • the image pickup device 2 picks up an optical image formed by the zoom lens 1 and outputs an electric signal.
  • the image pickup element 2 for example, a CCD or CMOS can be used.
  • the imaging device 10 moves a lens having a positive refractive power that constitutes a part of the second lens group G2 in a direction perpendicular to the optical axis Z, for example. You may make it further provide the blurring correction mechanism which correct
  • the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible.
  • the values of the radius of curvature, the surface interval, the refractive index, the Abbe number, the aspherical coefficient, etc. of each lens component are not limited to the values shown in the above numerical examples, and can take other values.

Abstract

[Problem] To achieve a lowered cost and favorable optical performance in a zoom lens. [Solution] A zoom lens essentially consisting of, in order from the object side, a first lens group (G1) having a negative refractive power and a second lens group (G2) having a positive refractive power, the gap between the first lens group (G1) and the second lens group (G2) changing when varying magnification, wherein plastic lenses are used for all of both the first lens group (G1) and the second lens group (G2), and both groups are configured from at least two lenses (the first lens group (G1) from lenses (L11, L12) and the second lens group from lenses (L21, L22, L23)). Additionally, when the amount of motion of the second lens group (G2) when varying magnification from the wide end to the tele end is M2 and the focal distance of the entire system at the tele end is ft, the following conditional expression is satisfied: 0.45 < M2/ft < 0.8.

Description

ズームレンズおよび撮像装置Zoom lens and imaging device
　本発明は、ズームレンズおよび撮像装置に関し、特に、小型のカメラや携帯端末装置に好適に使用可能なズームレンズおよび、そのようなズームレンズを備えた撮像装置に関するものである。 The present invention relates to a zoom lens and an imaging apparatus, and more particularly, to a zoom lens that can be suitably used for a small camera or a portable terminal apparatus, and an imaging apparatus including such a zoom lens.
　従来、コンパクトなデジタルカメラやビデオカメラ、携帯端末装置などに搭載されるズームレンズとして、負レンズ群先行（物体側に負レンズ群を配置した構成）の２群あるいは３群タイプのズームレンズが広く知られており、例えば特許文献１にはそれらの例が示されている。また特許文献２および３には、変倍比が３倍程度で、より簡易な２群タイプが採用された低コストのズームレンズの例として、第１レンズ群が２枚、第２レンズ群が３枚の計５枚のレンズで構成されたズームレンズが示されている。一方特許文献４には、第１レンズ群が２枚、第２レンズ群が２枚の計４枚のレンズで構成されたズームレンズが示されている。 2. Description of the Related Art Conventionally, as a zoom lens mounted on a compact digital camera, video camera, portable terminal device, etc., a two-group or three-group type zoom lens having a negative lens group preceding (a configuration in which a negative lens group is arranged on the object side) is widely used. For example, Patent Document 1 shows examples thereof. In Patent Documents 2 and 3, as an example of a low-cost zoom lens in which a zoom ratio is about 3 times and a simpler two-group type is adopted, there are two first lens groups and two second lens groups. A zoom lens composed of three lenses, a total of five lenses, is shown. On the other hand, Patent Document 4 shows a zoom lens composed of a total of four lenses, two first lens groups and two second lens groups.
　他方、特許文献５や６には、プラスチックレンズが採用されたズームレンズや、あるいはプラスチックレンズで構成することも想定して設計されたズームレンズが開示されている。特許文献５には、第１レンズ群を構成する３枚のレンズのうち１枚がプラスチックレンズとされた例が示されている。また特許文献６には、全てのレンズがプラスチックレンズで構成された例が示されている。 On the other hand, Patent Documents 5 and 6 disclose a zoom lens using a plastic lens, or a zoom lens designed on the assumption that the lens is composed of a plastic lens. Patent Document 5 shows an example in which one of the three lenses constituting the first lens group is a plastic lens. Patent Document 6 shows an example in which all lenses are made of plastic lenses.
特開２０１０－９１９４８号公報JP 2010-91948 A 特開２００７－２９３３６８号公報JP 2007-293368 A 特開２００７－１０８３９９号公報JP 2007-108399 A 特開２００７－７８８０１号公報JP 2007-78801 A 特開２００８－１１２０００号公報JP 2008-112000 A 特開２００７－１８７７４０号公報JP 2007-187740 A
　特許文献４に示されたズームレンズは、極めて少ないレンズ枚数で構成されているが、このようにレンズ枚数が少ないことにより単純に低コスト化が実現されるものではない。例えば、少ないレンズ枚数で構成すると、レンズ１枚当たりが担うパワーが強くなり、製造誤差や組立誤差の許容量が少なくなったり、レンズの加工難度が高くなったりして、結果的に生産コストが高くなってしまう可能性もある。 The zoom lens disclosed in Patent Document 4 is configured with an extremely small number of lenses. However, since the number of lenses is small as described above, cost reduction cannot be realized simply. For example, if the number of lenses is small, the power of each lens increases, and the tolerance of manufacturing errors and assembly errors decreases, and the processing difficulty of lenses increases, resulting in lower production costs. There is also the possibility of becoming high.
　レンズをより安価な材料、例えば、プラスチック材料で構成することも低コスト化の１つの手段であるが、少ないレンズ枚数で構成したときには、レンズ１枚当たりのパワーが強いため、コストの安いプラスチックを用いることが難しくなってしまう。それは、製造誤差や組立誤差、あるいは、温度変化に伴う光学諸元や性能の変動が大きくなったり、収差の補正バランスをとることが難しくなったりするためである。ここで、改めて特許文献４に示されているズームレンズの構成について考えると、第１レンズ群に配置された正レンズおよび負レンズ共に高屈折率の材料が用いられていることから分かるように、低コスト化に重点を置いて設計された訳ではなく、そこにも記載があるように、沈胴時の厚みを小さくすることを優先して設計されたものであることがわかる。 Constructing the lens with a less expensive material, for example, a plastic material, is one means of reducing the cost. However, when the lens is composed of a small number of lenses, the power per lens is strong, so a low-cost plastic is used. It becomes difficult to use. This is because variations in optical specifications and performance due to manufacturing errors, assembly errors, or changes in temperature become large, and it becomes difficult to balance aberration correction. Here, considering the configuration of the zoom lens shown in Patent Document 4 again, as can be seen from the fact that a high refractive index material is used for both the positive lens and the negative lens arranged in the first lens group, It is not designed with an emphasis on cost reduction, but it can be seen that it was designed with priority given to reducing the thickness when retracted, as described therein.
　逆に言えば、サイズよりも、光学性能やコストをより優先して考える場合には、特許文献４に示されるような第２群の正レンズのパワーを２枚のレンズに分散させた、特許文献２や３に示される第２群の構成の方が好ましいと考えられる。また、そのような構成とすることで、第２群に配置された正レンズ１枚当たりが担うパワーが小さくなるため、レンズをプラスチックから構成することも可能になる。しかし、特許文献２や３に示されたズームレンズも、第１レンズ群に配置されたレンズが高屈折率材料で構成されており、さらなる低コスト化の余地が残されている。 In other words, in the case where optical performance and cost are given priority over size, the power of the second lens group as shown in Patent Document 4 is distributed to two lenses. The configuration of the second group shown in Documents 2 and 3 is considered preferable. In addition, with such a configuration, the power that one positive lens arranged in the second group bears is reduced, so that the lens can be made of plastic. However, in the zoom lenses disclosed in Patent Documents 2 and 3, the lenses arranged in the first lens group are made of a high refractive index material, leaving room for further cost reduction.
　上述のようにプラスチックレンズを採用するためには、各レンズのパワーを最適に設定する必要がある。つまり、特許文献４に示されるズームレンズのように少ないレンズ枚数で構成し、かつ、コストの低いプラスチックレンズを採用する場合には、各レンズへのパワー配分を十分に考慮しなければならない。 In order to employ plastic lenses as described above, it is necessary to optimally set the power of each lens. In other words, when a plastic lens having a small number of lenses and a low cost is employed as in the zoom lens disclosed in Patent Document 4, power distribution to each lens must be sufficiently considered.
　プラスチックレンズが採用されたズームレンズの例としては、前述のように特許文献５や６に示されたものがあるが、それらの第１レンズ群は、特許文献２～４に示されているズームレンズの第１レンズ群よりもレンズ枚数が１枚多い構成となっている。このように、プラスチックレンズを用いる場合、前述した通り、パワーの強い１枚のレンズを２枚のレンズに分割することによりパワーを分散させて、ある程度までパワーが小さくなったレンズを適用するという考えもある。しかしそのような構成を採用すると、沈胴長は大きくなってしまう。また特許文献６には、全てのレンズがプラスチックレンズで構成された例が示されているが、その場合は、変倍比が２倍程度にとどまっている。 Examples of zoom lenses using plastic lenses include those described in Patent Documents 5 and 6 as described above, and those first lens groups are zoom lenses disclosed in Patent Documents 2 to 4. The number of lenses is one more than that of the first lens group of the lens. As described above, when using a plastic lens, as described above, the power is dispersed by dividing one lens having high power into two lenses, and a lens having a power reduced to a certain extent is applied. There is also. However, if such a configuration is adopted, the retractable length becomes large. Patent Document 6 shows an example in which all lenses are made of plastic lenses, but in that case, the zoom ratio is only about twice.
　本発明は上記の事情に鑑みてなされたものであり、少ないレンズ枚数で３倍乃至４倍程度の変倍比を確保しつつ、プラスチックレンズを採用して低コスト化を達成するとともに、各レンズのパワーを最適に設定することで良好な光学性能を実現できる２群ズームレンズを提供することを目的とする。 The present invention has been made in view of the circumstances described above, and achieves cost reduction by adopting a plastic lens while securing a zoom ratio of about 3 to 4 times with a small number of lenses, and each lens. An object of the present invention is to provide a two-group zoom lens that can realize good optical performance by optimally setting the power of the zoom lens.
　本発明による第１のズームレンズは、 
　実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて、
　前記第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、
　広角端から望遠端に変倍するときの第２レンズ群の移動量をＭ２、望遠端における全系の焦点距離をｆｔとしたとき、以下の条件式
　　　０．４５＜Ｍ２／ｆｔ＜０．８　…（１）
を満足することを特徴とするものである。 The first zoom lens according to the present invention comprises:
The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming. In zoom lenses where
Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses,
When the amount of movement of the second lens unit when zooming from the wide-angle end to the telephoto end is M2, and the focal length of the entire system at the telephoto end is ft, the following conditional expression 0.45 <M2 / ft <0.8 ... (1)
It is characterized by satisfying.
　ここで、「実質的に第１レンズ群と第２レンズ群とからなる」とは、それらのレンズ群以外に、実質的にパワーを有さないレンズ、絞りやカバーガラス等レンズ以外の光学要素、レンズフランジ、レンズバレル、撮像素子、手振れ補正機構等の機構部分等を持つ場合も含むものとする。この点は、後述する本発明の第２のズームレンズに関する記載や、さらには、「第１レンズ群が実質的に、物体側より順に、負の屈折力を有する第１レンズおよび正の屈折力を有する第２レンズの２枚より構成され」との記載についても同様である。 Here, “consisting essentially of the first lens group and the second lens group” means an optical element other than the lens group, such as a lens having substantially no power, a diaphragm, a cover glass, etc. In addition, a case where a mechanism portion such as a lens flange, a lens barrel, an image sensor, a camera shake correction mechanism, or the like is included is also included. This point relates to the second zoom lens of the present invention to be described later, and further, “the first lens group has a negative refractive power substantially in order from the object side and the positive refractive power. The same applies to the description of “consisting of two of the second lenses having”.
　なお、本発明のズームレンズにおける各レンズ群は、３枚以上のプラスチックレンズから構成されてもよい。また、各レンズ群を構成するレンズには接合レンズが用いられてもよいが、接合レンズはｎ枚の貼り合わせで構成されていれば、ｎ枚のレンズとして数えるものとする。また、本明細書における「本発明のズームレンズ」あるいは「本発明によるズームレンズ」との記載は、特にことわりがなければ本発明による第１のズームレンズおよび、後述する第２のズームレンズの双方を指すものとする。 Each lens group in the zoom lens of the present invention may be composed of three or more plastic lenses. In addition, a cemented lens may be used as a lens constituting each lens group. However, if the cemented lens is configured by bonding of n sheets, it is counted as n lenses. Further, in the present specification, the description of “the zoom lens of the present invention” or “the zoom lens of the present invention” refers to both the first zoom lens according to the present invention and the second zoom lens described later unless otherwise specified. Shall be pointed to.
　また、本発明のズームレンズにおけるレンズの面形状、屈折力の符号は、非球面が含まれているものについては近軸領域で考えるものとする。 In the zoom lens according to the present invention, the surface shape of the lens and the sign of the refractive power are considered in the paraxial region when an aspheric surface is included.
　ここで、本発明による上記第１のズームレンズは、望遠端における全系の焦点距離をｆｔ、前記第１レンズ群の焦点距離をｆ１としたとき、以下の条件式
　　　１．５＜｜ｆｔ／ｆ１｜＜２．３　…（２）
を満足するものであることがより望ましい。 Here, in the first zoom lens according to the present invention, when the focal length of the entire system at the telephoto end is ft and the focal length of the first lens group is f1, the following conditional expression 1.5 <| ft / f1 | <2.3 (2)
It is more desirable to satisfy the above.
　また、本発明による第２のズームレンズは、
　実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて、
　前記第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、
　望遠端における全系の焦点距離をｆｔ、第１レンズ群の焦点距離をｆ１としたとき、以下の条件式
　　　１．５＜｜ｆｔ／ｆ１｜＜２．３　…（２）
を満足することを特徴とするものである。 Further, the second zoom lens according to the present invention includes:
The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming. In zoom lenses where
Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses,
When the focal length of the entire system at the telephoto end is ft and the focal length of the first lens unit is f1, the following conditional expression 1.5 <| ft / f1 | <2.3 (2)
It is characterized by satisfying.
　なお、本発明による上記第２のズームレンズは、広角端から望遠端に変倍するときの第２レンズ群の移動量をＭ２、望遠端における全系の焦点距離をｆｔとしたとき、以下の条件式
　　　０．４５＜Ｍ２／ｆｔ＜０．８　…（１）
を満足するものであることが望ましい。 In the second zoom lens according to the present invention, when the amount of movement of the second lens unit when zooming from the wide-angle end to the telephoto end is M2, and the focal length of the entire system at the telephoto end is ft, the following Conditional expression 0.45 <M2 / ft <0.8 (1)
It is desirable to satisfy
　そして、本発明によるズームレンズは、第１レンズ群が少なくとも１枚の正レンズを有し、該正レンズのｄ線に対するアッベ数をνｄ１ｐとしたとき、以下の条件式
　　　νｄ１ｐ＜２９　…（３）
を満足するものであることが望ましい。 In the zoom lens according to the present invention, when the first lens group has at least one positive lens and the Abbe number of the positive lens with respect to the d-line is νd1p, the following conditional expression νd1p <29 (3)
It is desirable to satisfy
　また本発明によるズームレンズは、第２レンズ群が少なくとも１枚の負レンズを有し、該負レンズのｄ線に対するアッベ数をνｄ２ｎとしたとき、以下の条件式
　　　νｄ２ｎ＜２９　…（４）
を満足するものであることが望ましい。 In the zoom lens according to the present invention, when the second lens group has at least one negative lens, and the Abbe number of the negative lens with respect to the d-line is νd2n, the following conditional expression νd2n <29 (4)
It is desirable to satisfy
　さらに本発明によるズームレンズは、第１レンズ群が実質的に、物体側より順に、負の屈折力を有する第１レンズおよび正の屈折力を有する第２レンズの２枚より構成され、該２枚のレンズの光軸上での空気間隔をｄ２、広角端における全系の焦点距離をｆｗとしたとき、以下の条件式
　　　０．３１＜ｄ２／ｆｗ＜０．７０　…（５）
を満足するものであることが望ましい。 Further, in the zoom lens according to the present invention, the first lens group is composed of two lenses, a first lens having a negative refractive power and a second lens having a positive refractive power, in order from the object side. When the air interval on the optical axis of the single lens is d2, and the focal length of the entire system at the wide angle end is fw, the following conditional expression 0.31 <d2 / fw <0.70 (5)
It is desirable to satisfy
　また本発明によるズームレンズは、広角端および望遠端の焦点距離をそれぞれｆｗ、ｆｔとしたとき、以下の条件式
　　　２．０＜ｆｔ／ｆｗ＜５．０　…（６）
を満足するものであることが望ましい。 In the zoom lens according to the present invention, when the focal lengths at the wide-angle end and the telephoto end are fw and ft, respectively, the following conditional expression 2.0 <ft / fw <5.0 (6)
It is desirable to satisfy
　なお上記条件式（３）～（６）は、それらの中の一部（１つまたは複数）が満足されてもよい。そしてそれらの条件式（３）、（４）、（５）および（６）で示した各条件のより望ましい範囲は下記の通りである。 The conditional expressions (3) to (6) may satisfy a part (one or more) of them. The more desirable ranges of the conditions indicated by the conditional expressions (3), (4), (5) and (6) are as follows.
　　　νｄ１ｐ＜２６　…（３’）
　　　νｄ２ｎ＜２６　…（４’）
　　　０．３１＜ｄ２／ｆｗ＜０．６０　…（５’）
　　　２．３＜ｆｔ／ｆｗ＜５．０　…（６’）
　また本発明のズームレンズにおいては、無限遠から近距離へのフォーカシングに際して、第２レンズ群全体、または第２レンズ群に配置された一部のレンズを光軸に沿って移動させる構成となっていることが好ましい。より具体的には、第２レンズ群を物体側より順に、正の屈折力を有する第３レンズ、負の屈折力を有する第４レンズ、正の屈折力を有する第５レンズより構成したとき、第５レンズのみを光軸に沿って移動させる構成であることが好ましい。 νd1p <26 (3 ′)
νd2n <26 (4 ′)
0.31 <d2 / fw <0.60 (5 ′)
2.3 <ft / fw <5.0 (6 ′)
In the zoom lens according to the present invention, the entire second lens group or a part of the lenses arranged in the second lens group is moved along the optical axis when focusing from infinity to a short distance. It is preferable. More specifically, when the second lens group is composed of a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power in order from the object side, It is preferable that only the fifth lens be moved along the optical axis.
　さらに本発明のズームレンズは、第１レンズ群が少なくとも１枚の負レンズを有し、該負レンズのｄ線に対する屈折率およびアッベ数をそれぞれ、ｎｄ１ｎ、νｄ１ｎとしたとき、以下の条件式
　　　１．４８＜ｎｄ１ｎ＜１．５６　…（７）
　　　５０＜νｄ１ｎ＞６０　…（８）
を満足するものであることが好ましい。 Furthermore, in the zoom lens of the present invention, when the first lens group has at least one negative lens, and the refractive index and Abbe number of the negative lens with respect to the d-line are nd1n and νd1n, respectively, the following conditional expression 1 .48 <nd1n <1.56 (7)
50 <νd1n> 60 (8)
Is preferably satisfied.
　また本発明のズームレンズは、第２レンズ群が少なくとも１枚の正レンズを有し、該正レンズのｄ線に対する屈折率およびアッベ数をそれぞれ、ｎｄ２ｐ、νｄ２ｐしたとき、以下の条件式
　　　１．４８＜ｎｄ２ｐ＜１．５６　…（９）
　　　５０＜νｄ２ｐ＜６０　…（１０）
を満足するものであることが好ましい。 In the zoom lens of the present invention, when the second lens group has at least one positive lens, and the refractive index and Abbe number for the d-line of the positive lens are nd2p and νd2p, respectively, 48 <nd2p <1.56 (9)
50 <νd2p <60 (10)
Is preferably satisfied.
　また本発明のズームレンズにおいては、第１レンズ群が物体側より順に、負の屈折力を有する第１レンズ、正の屈折力を有する第２レンズから構成され、第１レンズのｄ線に対する屈折率、アッベ数を各々ｎｄ１１、νｄ１１とし、第２レンズのｄ線に対する屈折率、アッベ数を各々ｎｄ１２、νｄ１２としたとき、それらのレンズが下記条件
　　　１．４８＜ｎｄ１１＜１．６１　…（１１）
　　　５０＜νｄ１１　…（１２）より好ましくは　５２＜νｄ１１　…（１２’）
　　　１．５６＜ｎｄ１２＜１．６６　…（１３）
　　　νｄ１２＜３３　…（１４）より好ましくは　νｄ１２＜２９　…（１４’）
を満足するプラスチック材料から形成されることが望ましい。 In the zoom lens according to the present invention, the first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power. When the refractive index and Abbe number are nd11 and νd11, respectively, and the refractive index and Abbe number of the second lens are nd12 and νd12, respectively, the lenses satisfy the following conditions: 1.48 <nd11 <1.61 (11) )
50 <νd11 (12), more preferably 52 <νd11 (12 ′)
1.56 <nd12 <1.66 (13)
νd12 <33 (14), more preferably νd12 <29 (14 ′)
It is desirable to be formed from a plastic material that satisfies
　また本発明のズームレンズにおいては、第２レンズ群が物体側より順に、正の屈折力を有する第３レンズ、負の屈折力を有する第４レンズ、正の屈折力を有する第５レンズから構成され、第３レンズのｄ線に対する屈折率、アッベ数を各々ｎｄ２１、νｄ２１とし、第４レンズのｄ線に対する屈折率、アッベ数を各々ｎｄ２２、νｄ２２とし、第５レンズのｄ線に対する屈折率、アッベ数を各々ｎｄ２３、νｄ２３としたとき、それらのレンズは下記条件
　　　１．４８＜ｎｄ２１＜１．６１　…（１５）
　　　５０＜νｄ２１　…（１６）より好ましくは５２＜νｄ２１　…（１６’）
　　　１．５６＜ｎｄ２２＜１．６８　…（１７）
　　　νｄ２２＜３３　…（１８）より好ましくはνｄ２２＜２９　…（１８’）
　　　１．４８＜ｎｄ２３＜１．６１　…（１９）
　　　５０＜νｄ２３　…（２０）より好ましくは５２＜νｄ２３　…（２０’）
を満足するプラスチック材料から形成されることが望ましい。 In the zoom lens of the present invention, the second lens group includes, in order from the object side, a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power. The third lens has a refractive index with respect to the d-line and Abbe numbers of nd21 and νd21, respectively, and the fourth lens has a refractive index with respect to the d-line and Abbe numbers of nd22 and νd22, respectively. When the Abbe numbers are nd23 and νd23, these lenses satisfy the following conditions: 1.48 <nd21 <1.61 (15)
50 <νd21 (16), more preferably 52 <νd21 (16 ′)
1.56 <nd22 <1.68 (17)
νd22 <33 (18), more preferably νd22 <29 (18 ′)
1.48 <nd23 <1.61 (19)
50 <νd23 (20), more preferably 52 <νd23 (20 ′)
It is desirable to be formed from a plastic material that satisfies
　他方、本発明による撮像装置は、以上説明した本発明による第１あるいは第２のズームレンズを備えたことを特徴とするものである。 On the other hand, an imaging apparatus according to the present invention is characterized by including the first or second zoom lens according to the present invention described above.
　本発明による第１のズームレンズは実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて、第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、その上で前記条件式（１）を満足するものとされているので、プラスチックレンズを採用して低コスト化を達成するとともに、少ないレンズ枚数で３倍乃至４倍程度の変倍比を確保しつつ、各レンズのパワーを最適に設定することで良好な光学性能を実現できるものとなる。 The first zoom lens according to the present invention substantially includes, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. In the zoom lens in which the distance between the lens group and the second lens group changes, each of the first lens group and the second lens group is composed of at least two lenses by applying a plastic lens, on which the above-described lens is arranged. Since it is assumed that the conditional expression (1) is satisfied, a plastic lens is used to achieve cost reduction, and each lens is secured while maintaining a zoom ratio of about 3 to 4 times with a small number of lenses. Optimum power can be set to achieve good optical performance.
　以下、上に述べた効果についてさらに詳しく説明する。条件式（１）は、第２レンズ群の移動量と望遠端における全系の焦点距離の関係を規定しており、条件式の下限値以下になると、変倍比を大きくすることが困難になる。またその場合は、第２レンズ群のパワーを強くしなければならず、製造誤差や組立誤差の許容量が少なくなってしまうため好ましくない。さらにその場合は、プラスチックレンズのパワーが強くなり、温度による光学性能や特性の変化が大きくなるため、好ましくない。逆に、条件式の上限値以上になると、第２レンズ群の移動量が大きくなり、レンズ系が大型化するため好ましくない。条件式（１）を満足している場合は、以上の不具合を防止して、上記の効果が得られようになる。 Hereinafter, the effects described above will be described in more detail. Conditional expression (1) defines the relationship between the amount of movement of the second lens unit and the focal length of the entire system at the telephoto end. If the lower limit of the conditional expression is not reached, it is difficult to increase the zoom ratio. Become. In this case, the power of the second lens group must be increased, which is not preferable because the tolerance for manufacturing errors and assembly errors is reduced. Further, in that case, the power of the plastic lens becomes strong, and the change in optical performance and characteristics due to temperature increases, which is not preferable. On the other hand, if the upper limit value of the conditional expression is exceeded, the amount of movement of the second lens group increases and the lens system becomes larger, which is not preferable. When the conditional expression (1) is satisfied, the above-described problems can be prevented and the above effect can be obtained.
　また、本発明による第１のズームレンズにおいて特に、前記条件式（２）を満足している場合は、上記の効果がより顕著なものとなる。すなわちこの条件式（２）は、望遠端における全系の焦点距離と第１レンズ群の焦点距離の関係を規定しており、下限値以下になると、変倍時の移動量が大きくなり、レンズ系が大型化してしまうため好ましくない。逆に上限値以上になると、主に、広角端近傍での像面湾曲の補正が困難になる。また、プラスチックレンズのパワーが強くなり、温度による光学性能や特性の変化が大きくなるため、好ましくない。条件式（２）を満足している場合は、以上の不具合も防止できるので、上記の効果をより顕著なものとすることができる。 In the first zoom lens according to the present invention, particularly, when the conditional expression (2) is satisfied, the above effect becomes more remarkable. In other words, this conditional expression (2) defines the relationship between the focal length of the entire system at the telephoto end and the focal length of the first lens group. This is not preferable because the system becomes large. On the other hand, when the upper limit value is exceeded, it becomes difficult to correct curvature of field mainly near the wide-angle end. Further, the power of the plastic lens becomes strong, and the optical performance and characteristics change with temperature, which is not preferable. When the conditional expression (2) is satisfied, the above problems can be prevented, and the above effect can be made more remarkable.
　他方、本発明による第２のズームレンズは実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、その上で前記条件式（２）を満足するものとされているので、プラスチックレンズを採用して低コスト化を達成するとともに、少ないレンズ枚数で３倍乃至４倍程度の変倍比を確保しつつ、各レンズのパワーを最適に設定することで良好な光学性能を実現できるという効果を奏する。すなわち、この場合も条件式（２）を満足することにより、先に述べた通りの問題つまり、レンズ系が大型化してしまう、広角端近傍での像面湾曲の補正が困難になる、温度による光学性能や特性の変化が大きくなるといった問題を防止して、上記効果を得ることができる。 On the other hand, the second zoom lens according to the present invention substantially comprises, in order from the object side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. In the zoom lens in which the distance between the first lens group and the second lens group is changed, each of the first lens group and the second lens group is composed of at least two lenses by applying a plastic lens. Since the conditional expression (2) is satisfied, a plastic lens is used to achieve a reduction in cost, and a zoom ratio of about 3 to 4 times is secured with a small number of lenses. By setting the lens power optimally, there is an effect that good optical performance can be realized. That is, also in this case, satisfying the conditional expression (2) causes the problem as described above, that is, the lens system becomes large, and it becomes difficult to correct the curvature of field near the wide-angle end. The above effect can be obtained by preventing problems such as a large change in optical performance and characteristics.
　この本発明による第２のズームレンズにおいて特に、前記条件式（１）を満足している場合は、前記第１のズームレンズにおいて特に条件式（２）を満足している場合と同じ効果を得ることができる。 Particularly in the second zoom lens according to the present invention, when the conditional expression (1) is satisfied, the same effect as that when the conditional expression (2) is particularly satisfied in the first zoom lens is obtained. be able to.
　次に条件式（３）～（２０）による効果について説明する。 Next, effects of conditional expressions (3) to (20) will be described.
　条件式（３）は、第１レンズ群内に配置される少なくとも１枚の正レンズのアッベ数を規定しており、条件式の範囲を外れると、特に倍率色収差が大きくなるため、好ましくない。条件式（３）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (3) prescribes the Abbe number of at least one positive lens arranged in the first lens group, and it is not preferable to deviate from the conditional expression because chromatic aberration of magnification becomes particularly large. When the conditional expression (3) is satisfied, the above problem can be prevented.
　条件式（４）は、第２レンズ群内に配置される少なくとも１枚の負レンズのアッベ数を規定しており、条件式の範囲を外れると、特に軸上色収差が大きくなるため、好ましくない。条件式（４）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (4) defines the Abbe number of at least one negative lens arranged in the second lens group, and if it falls outside the range of the conditional expression, axial chromatic aberration increases, which is not preferable. . When the conditional expression (4) is satisfied, the above problem can be prevented.
　条件式（５）は、第１レンズ群に配置された第１レンズと第２レンズの間隔と、広角端における全系の焦点距離との関係を規定しており、その下限値以下になると、コンパクト化には有利になるが、球面収差の補正が難しくなるため好ましくない。逆に上限値以上になると、第１レンズ群全体が大型化してしまうため、好ましくない。条件式（５）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (5) defines the relationship between the distance between the first lens and the second lens arranged in the first lens group and the focal length of the entire system at the wide-angle end. Although it is advantageous for downsizing, it is not preferable because correction of spherical aberration becomes difficult. On the other hand, if the upper limit value is exceeded, the entire first lens group will be enlarged, which is not preferable. When the conditional expression (5) is satisfied, the above problem can be prevented.
　条件式（６）は、広角端および望遠端の各焦点距離の関係、つまり変倍比を規定しており、下限値以下になると、ズームレンズとしての有意性が小さくなってしまう。逆に上限値以上になると、レンズ系が大型化してしまう。また、このズームタイプにおいては、望遠端において明るさの低下が大きくなり過ぎてしまい、好ましくない。また、望遠端において、ある程度の明るさを確保しようとすれば、第２レンズ群への負担が大きくなり、少ないレンズ枚数での収差補正が困難になってしまう。条件式（６）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (6) defines the relationship between the focal lengths at the wide-angle end and the telephoto end, that is, the zoom ratio, and if it is below the lower limit value, the significance as a zoom lens is reduced. On the other hand, if the upper limit is exceeded, the lens system becomes large. In addition, this zoom type is not preferable because the brightness decreases excessively at the telephoto end. Also, if it is attempted to secure a certain level of brightness at the telephoto end, the burden on the second lens group becomes large, and aberration correction with a small number of lenses becomes difficult. When the conditional expression (6) is satisfied, the above problem can be prevented.
　以上述べた条件式（３）、（４）、（５）および（６）による効果は、各条件式が規定する範囲の中で特にそれぞれ条件式（３’）、（４’）、（５’）および（６’）が満足されている場合は、より顕著なものとなる。 The effects of the conditional expressions (3), (4), (5) and (6) described above are particularly the conditional expressions (3 ′), (4 ′) and (5), respectively, within the range defined by each conditional expression. If ') and (6') are satisfied, it becomes more prominent.
　また、第１レンズ群に配された負レンズの屈折率ｎｄ１ｎが条件式（７）の下限値以下になると、レンズの曲率（近似曲率）が大きくなって像面湾曲および歪曲収差の補正が困難になる。逆に上限値以上になると、非点収差や倍率色収差の補正のバランスをとることが困難になり、好ましくない。条件式（７）を満足している場合は、上記の不具合を防止することができる。 Further, when the refractive index nd1n of the negative lens arranged in the first lens group is equal to or lower than the lower limit value of the conditional expression (7), the curvature of the lens (approximate curvature) becomes large and it is difficult to correct curvature of field and distortion. become. On the other hand, if the value exceeds the upper limit, it is difficult to balance astigmatism and lateral chromatic aberration correction, which is not preferable. When the conditional expression (7) is satisfied, the above problem can be prevented.
　また、第１レンズ群に配された負レンズのアッベ数νｄ１ｎが条件式（８）の範囲を外れると、特に広角端近傍での倍率色収差の補正が困難になるが、条件式（８）を満足している場合はこの不具合を防止することができる。 Further, if the Abbe number νd1n of the negative lens arranged in the first lens group is out of the range of the conditional expression (8), it is difficult to correct the lateral chromatic aberration particularly near the wide-angle end, but the conditional expression (8) When satisfied, this problem can be prevented.
　また、第２レンズ群に配された正レンズの屈折率ｎｄ２ｐが条件式（９）の下限値以下になると、レンズの曲率（近似曲率）が大きくなり、収差発生量が大きくなってしまう。逆に上限値以上になると、非点収差が大きくなるので好ましくない。条件式（９）を満足している場合は、上記の不具合を防止することができる。 In addition, when the refractive index nd2p of the positive lens arranged in the second lens group is equal to or lower than the lower limit value of the conditional expression (9), the curvature of the lens (approximate curvature) increases and the amount of aberration generated increases. On the other hand, when the value exceeds the upper limit, astigmatism increases, which is not preferable. When the conditional expression (9) is satisfied, the above problem can be prevented.
　また、第２レンズ群に配された正レンズのアッベ数νｄ２ｐが条件式（１０）の範囲を外れると、軸上色収差の補正が困難になるが、条件式（１０）を満足している場合はこの不具合を防止することができる。 If the Abbe number νd2p of the positive lens arranged in the second lens group is out of the range of the conditional expression (10), it is difficult to correct axial chromatic aberration, but the conditional expression (10) is satisfied. Can prevent this problem.
　また本発明のズームレンズにおいて特に、第１レンズ群が物体側より順に、負の屈折力を有する第１レンズ、正の屈折力を有する第２レンズから構成された上で、前記条件式（１１）～（１４）を満足している場合は、下記の効果を得ることができる。条件式（１１）および条件式（１３）はそれぞれ、第１レンズの屈折率、第２レンズの屈折率を規定しており、それらの条件式の下限値以下になると、収差の発生が大きくなってしまうとともに、レンズの曲率（近似曲率）が大きくなって、第１レンズ群が厚くなってしまうため好ましくない。また、低コスト化や軽量化等の目的によって、第１レンズ群に配置された２枚のレンズをプラスチックレンズで構成しようとする場合、それらの条件式の上限値以上となるような材料で構成すると、非点収差や倍率色収差の補正のバランスをとることが困難になり、好ましくない。条件式（１１）あるいは（１３）を満足している場合は、以上の不具合を防止することができる。 In the zoom lens according to the present invention, in particular, the first lens group includes, in order from the object side, a first lens having a negative refractive power and a second lens having a positive refractive power, and the conditional expression (11 ) To (14), the following effects can be obtained. Conditional expression (11) and conditional expression (13) define the refractive index of the first lens and the refractive index of the second lens, respectively, and the occurrence of aberration increases when the conditional expression is below the lower limit of these conditional expressions. In addition, the curvature of the lens (approximate curvature) increases and the first lens group becomes thick. In addition, when the two lenses arranged in the first lens group are to be composed of plastic lenses for the purpose of cost reduction and weight reduction, they are composed of a material that exceeds the upper limit value of the conditional expressions. Then, it becomes difficult to balance the correction of astigmatism and lateral chromatic aberration, which is not preferable. When the conditional expression (11) or (13) is satisfied, the above problems can be prevented.
　条件式（１２）および条件式（１４）はそれぞれ、第１レンズのアッベ数、第２レンズのアッベ数を規定しており、それらの条件式の範囲を外れると、第１レンズと第２レンズとのアッベ数の差が小さくなり、色収差の補正が困難になる。また、条件式（１２）あるいは（１４）の範囲を外れると、色収差補正のために、第１レンズ群に配置された他方のレンズ（条件式（１４）で第２レンズのアッベ数を規定する場合は第１レンズがこの「他方のレンズ」であり、条件式（１２）で第１レンズのアッベ数を規定する場合は第２レンズがこの「他方のレンズ」である）のパワーも強くする必要があり、特に、広角端において像面湾曲や歪曲収差の補正が困難になるため、好ましくない。条件式（１２）あるいは（１４）を満足している場合は、以上の不具合を防止することができる。 Conditional expression (12) and conditional expression (14) define the Abbe number of the first lens and the Abbe number of the second lens, respectively, and the first lens and the second lens are out of the range of these conditional expressions. And the Abbe number difference becomes small, and correction of chromatic aberration becomes difficult. If the range of the conditional expression (12) or (14) is exceeded, the Abbe number of the second lens is defined by the other lens (conditional expression (14)) arranged in the first lens group in order to correct chromatic aberration. In this case, the first lens is the “other lens”, and when the Abbe number of the first lens is defined by the conditional expression (12), the power of the second lens is the “other lens”. In particular, it is difficult to correct curvature of field and distortion at the wide-angle end, which is not preferable. When the conditional expression (12) or (14) is satisfied, the above problems can be prevented.
　以上述べた効果は、条件式（１２）、（１４）の範囲の中で特にそれぞれ、条件式（１２’）、（１４’）が満足されている場合は、より顕著なものとなる。 The effects described above become more prominent when conditional expressions (12 ') and (14') are satisfied, respectively, within the ranges of conditional expressions (12) and (14).
　また本発明のズームレンズにおいて特に、第２レンズ群が物体側より順に、正の屈折力を有する第３レンズ、負の屈折力を有する第４レンズ、正の屈折力を有する第５レンズより構成された上で、前記条件式（１５）～（２０）が満足されている場合は、像面湾曲や球面収差をバランス良く補正する上で有利となる。 In the zoom lens of the present invention, in particular, the second lens group includes, in order from the object side, a third lens having a positive refractive power, a fourth lens having a negative refractive power, and a fifth lens having a positive refractive power. In addition, if the conditional expressions (15) to (20) are satisfied, it is advantageous for correcting field curvature and spherical aberration in a well-balanced manner.
　以上述べた効果は、条件式（１６）、（１８）、（２０）の範囲の中で特にそれぞれ、条件式（１６’）、（１８’）、（２０’）が満足されている場合は、より顕著なものとなる。 The above-described effects are obtained when conditional expressions (16 ′), (18 ′), and (20 ′) are satisfied, respectively, within the ranges of conditional expressions (16), (18), and (20). , Become more prominent.
　また本発明のズームレンズにおいて特に、無限遠から近距離へのフォーカシングに際して、第２レンズ群全体、または、第２レンズ群に配置された一部のレンズを光軸に沿って移動させる構成となっている場合は、下記の効果を得ることができる。すなわち、第１レンズ群全体を繰り出してフォーカスする構成を採用した場合は、第１レンズ群の有効径が大きくなったり、外径の大きなレンズを動かす必要が生じたりするが、第２レンズ群全体、または、第２レンズ群に配置された一部のレンズを移動させる場合は、そのような問題を回避することが可能になる。 In the zoom lens of the present invention, in particular, when focusing from infinity to a short distance, the entire second lens group or a part of the lenses arranged in the second lens group is moved along the optical axis. If so, the following effects can be obtained. That is, when the configuration in which the entire first lens group is extended and focused is adopted, the effective diameter of the first lens group becomes large or the lens having a large outer diameter needs to be moved. Alternatively, when a part of the lenses arranged in the second lens group is moved, such a problem can be avoided.
　以上の効果は、第２レンズ群を物体側より順に、正の屈折力を有する第３レンズ、負の屈折力を有する第４レンズ、正の屈折力を有する第５レンズより構成し、第５レンズのみを光軸に沿って移動させる構成とした場合に、より顕著なものとなる。 The above effect is that the second lens group is composed of a third lens having positive refractive power, a fourth lens having negative refractive power, and a fifth lens having positive refractive power in order from the object side. This is more noticeable when only the lens is moved along the optical axis.
　他方、本発明による撮像装置は、以上説明した効果を奏する本発明のズームレンズを備えたものであるから、良好な光学性能を備えた上で低コスト化を達成できるものとなる。 On the other hand, since the image pickup apparatus according to the present invention includes the zoom lens according to the present invention that achieves the above-described effects, it is possible to achieve cost reduction while providing good optical performance.
本発明の実施例１にかかるズームレンズのレンズ構成を示す断面図Sectional view showing the lens configuration of the zoom lens according to Example 1 of the present invention. 本発明の実施例２にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 2 of this invention. 本発明の実施例３にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 3 of this invention. 本発明の実施例４にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 4 of this invention. 本発明の実施例５にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 5 of this invention. 本発明の実施例６にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 6 of this invention. 本発明の実施例７にかかるズームレンズのレンズ構成を示す断面図Sectional drawing which shows the lens structure of the zoom lens concerning Example 7 of this invention. （Ａ）～（Ｈ）は本発明の実施例１のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens of Example 1 of the present invention. （Ａ）～（Ｈ）は本発明の実施例２のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens according to Example 2 of the present invention. （Ａ）～（Ｈ）は本発明の実施例３のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens according to Example 3 of the present invention. （Ａ）～（Ｈ）は本発明の実施例４のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens according to Example 4 of the present invention. （Ａ）～（Ｈ）は本発明の実施例５のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens according to Example 5 of the present invention. （Ａ）～（Ｈ）は本発明の実施例６のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens according to Example 6 of the present invention. （Ａ）～（Ｈ）は本発明の実施例７のズームレンズの各収差図(A) to (H) are aberration diagrams of the zoom lens of Example 7 of the present invention. 本発明の実施形態にかかる撮像装置の概略構成図1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention.
　以下、本発明の実施形態について図面を参照して詳細に説明する。図１は、本発明の実施形態にかかるズームレンズの構成例を示す断面図であり、後述の実施例１のズームレンズに対応している。また、図２～図７は、本発明の実施形態にかかる別の構成例を示す断面図であり、それぞれ後述の実施例２～７のズームレンズに対応している。図１～図７に示す例の基本的な構成は、図２および図７の実施例では第２レンズ群Ｇ２が２枚のレンズからなる点を除いて、その他は互いに同様であり、図示方法も同様であるので、ここでは主に図１を参照しながら、本発明の実施形態にかかるズームレンズについて説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a configuration example of a zoom lens according to an embodiment of the present invention, and corresponds to a zoom lens of Example 1 described later. 2 to 7 are cross-sectional views showing other configuration examples according to the embodiment of the present invention, which respectively correspond to zoom lenses of Examples 2 to 7 described later. The basic configuration of the example shown in FIGS. 1 to 7 is the same as that of the embodiment shown in FIGS. 2 and 7 except that the second lens group G2 includes two lenses. Therefore, the zoom lens according to the embodiment of the present invention will be described mainly with reference to FIG.
　図１では、左側が物体側、右側が像側として、（Ａ）は無限遠合焦状態でかつ広角端（最短焦点距離状態）での光学系配置を、（Ｂ）は無限遠合焦状態でかつ望遠端（最長焦点距離状態）での光学系配置を示している。これは、後述する図２～７においても同様である。 In FIG. 1, the left side is the object side, the right side is the image side, (A) is the infinitely focused state and the optical system arrangement at the wide angle end (shortest focal length state), and (B) is the infinitely focused state. And the arrangement of the optical system at the telephoto end (longest focal length state). The same applies to FIGS. 2 to 7 described later.
　本発明の実施形態にかかるズームレンズは、物体側から順に、負の屈折力を有する第１レンズ群Ｇ１と、正の屈折力を有する第２レンズ群Ｇ２とがレンズ群として配列されてなる。また第２レンズ群Ｇ２には、開口絞りＳｔが含まれている。ここに示す開口絞りＳｔは必ずしも大きさや形状を表すものではなく、光軸Ｚ上の位置を示すものである。 The zoom lens according to the embodiment of the present invention includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power arranged as a lens group. The second lens group G2 includes an aperture stop St. The aperture stop St shown here does not necessarily indicate the size or shape, but indicates the position on the optical axis Z.
　なお、図１には、第２レンズ群Ｇ２と像面Ｓｉｍとの間に、平行平板状の光学部材ＰＰが配置された例を示している。ズームレンズを撮像装置に適用する際には、レンズを装着するカメラ側の構成に応じて、光学系と像面Ｓｉｍの間にカバーガラス、赤外線カットフィルタやローパスフィルタなどの各種フィルタ等を配置することが好ましい。光学部材ＰＰは、これらカバーガラスや各種フィルタ等を想定したものである。また、近年の撮像装置は高画質化のために各色毎にＣＣＤを用いる３ＣＣＤ方式を採用しているものがあり、この３ＣＣＤ方式に対応するためには、色分解プリズム等の色分解光学系をレンズ系と像面Ｓｉｍの間に挿入することになる。その場合には、光学部材ＰＰの位置に色分解光学系を配置してもよい。 FIG. 1 shows an example in which a parallel plate-shaped optical member PP is disposed between the second lens group G2 and the image plane Sim. When applying a zoom lens to an image pickup apparatus, various filters such as a cover glass, an infrared cut filter, and a low-pass filter are arranged between the optical system and the image plane Sim according to the configuration of the camera on which the lens is mounted. It is preferable. The optical member PP assumes such cover glass and various filters. In recent years, some image pickup apparatuses employ a 3CCD system that uses a CCD for each color in order to improve image quality. In order to support this 3CCD system, a color separation optical system such as a color separation prism is used. It is inserted between the lens system and the image plane Sim. In that case, a color separation optical system may be arranged at the position of the optical member PP.
　このズームレンズは、広角端から望遠端に変倍する際に、第１レンズ群Ｇ１は像面Ｓｉｍ側に凸状の軌跡を描くように移動し、第２レンズ群Ｇ２は物体側に単調移動し、開口絞りＳｔは第２レンズ群Ｇ２と一体で移動するように構成されている。図１には、広角端から望遠端へ変倍するときの第１レンズ群Ｇ１および第２レンズ群Ｇ２の移動軌跡を、（Ａ）と（Ｂ）との間に付した実線の矢印で模式的に示している。 When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves so as to draw a convex locus on the image plane Sim side, and the second lens group G2 monotonously moves toward the object side. The aperture stop St is configured to move integrally with the second lens group G2. In FIG. 1, the movement trajectories of the first lens group G1 and the second lens group G2 when zooming from the wide-angle end to the telephoto end are schematically shown by solid line arrows between (A) and (B). Is shown.
　第１レンズ群Ｇ１は、物体側から順に配置された、負の屈折力を有する第１レンズＬ１１と、正の屈折力を有する第２レンズＬ１２とから構成されている。ここで、例えば図１に示す例のように、第１レンズＬ１１は両凹形状のレンズとし、第２レンズＬ１２は正メニスカス形状のレンズとすることができる。本発明のズームレンズにおいて第１レンズ群Ｇ１は、少なくとも２枚のレンズから構成されるが、本ズームレンズにおいては上述の通り２枚のレンズＬ１１、Ｌ１２から第１レンズ群Ｇ１が構成され、そしてそれらの双方がプラスチックレンズとされている。 The first lens group G1 includes a first lens L11 having a negative refractive power and a second lens L12 having a positive refractive power, which are arranged in order from the object side. Here, for example, as in the example shown in FIG. 1, the first lens L11 can be a biconcave lens, and the second lens L12 can be a positive meniscus lens. In the zoom lens of the present invention, the first lens group G1 is composed of at least two lenses. In the present zoom lens, the first lens group G1 is composed of the two lenses L11 and L12 as described above, and Both of them are plastic lenses.
　本発明のズームレンズにおいては、第２レンズ群Ｇ２が少なくとも２枚のレンズより構成されるが、図１の構成における第２レンズ群Ｇ２は、物体側より順に配置された、正の屈折力を有する第３レンズＬ２１、負の屈折力を有する第４レンズＬ２２、および正の屈折力を有する第５レンズＬ２３より構成されている。例えば図１の例のように上記第３レンズＬ２１は両凸形状のレンズ、上記第４レンズＬ２２は両凹形状のレンズ、第５レンズＬ２３は正メニスカス形状のレンズとすることができる。そして、第２レンズ群Ｇ２の全てのレンズＬ２１、Ｌ２２、およびＬ２３も全てプラスチックレンズとされている。 In the zoom lens of the present invention, the second lens group G2 is composed of at least two lenses, but the second lens group G2 in the structure of FIG. 1 has a positive refractive power arranged in order from the object side. The third lens L21 includes a fourth lens L22 having a negative refractive power, and a fifth lens L23 having a positive refractive power. For example, as in the example of FIG. 1, the third lens L21 can be a biconvex lens, the fourth lens L22 can be a biconcave lens, and the fifth lens L23 can be a positive meniscus lens. All the lenses L21, L22, and L23 of the second lens group G2 are also plastic lenses.
　以上説明のように、第１レンズ群Ｇ１を２枚のレンズＬ１１およびＬ１２から、そして第２レンズ群Ｇ２を３枚のレンズＬ２１、Ｌ２２およびＬ２３から構成した上で、それらのレンズを全てプラスチックレンズとすることにより、低コスト化を達成することができる。 As described above, the first lens group G1 is composed of the two lenses L11 and L12 and the second lens group G2 is composed of the three lenses L21, L22 and L23, and these lenses are all plastic lenses. Thus, cost reduction can be achieved.
　なお、図１～７の構成のうち特に図２および図７の構成では、その他の構成と異なって、第２レンズ群Ｇ２が２枚のレンズつまり第３レンズＬ２１および第４レンズＬ２２から構成されているが、この構成においても上記の効果を得ることができる。 1 to 7, especially in the configurations of FIGS. 2 and 7, unlike the other configurations, the second lens group G2 includes two lenses, that is, the third lens L21 and the fourth lens L22. However, the above effect can also be obtained with this configuration.
　また本ズームレンズは、広角端から望遠端に変倍するときの第２レンズ群Ｇ２の移動量をＭ２、望遠端における全系の焦点距離をｆｔとして、以下の条件式
　　　０．４５＜Ｍ２／ｆｔ＜０．８　…（１）
を満足している。また本ズームレンズは、望遠端における全系の焦点距離をｆｔ、第１レンズ群Ｇ１の焦点距離をｆ１として、以下の条件式
　　　１．５＜｜ｆｔ／ｆ１｜＜２．３　…（２）
を満足している。 In this zoom lens, the following conditional expression 0.45 <M 2 / M ft <0.8 (1)
Is satisfied. In this zoom lens, if the focal length of the entire system at the telephoto end is ft and the focal length of the first lens group G1 is f1, the following conditional expression 1.5 <| ft / f1 | <2.3 (2)
Is satisfied.
　なお、以上の条件式（１）および（２）で規定される各条件の数値例を、実施例毎にまとめて表２２に示してある。またこの表２２には、後述する条件式（３）～（２０）で規定される各条件の数値例も併せて示してある。 Note that numerical examples of the conditions defined by the above conditional expressions (1) and (2) are shown in Table 22 for each example. Table 22 also shows numerical examples of conditions defined by conditional expressions (3) to (20) described later.
　そして本ズームレンズでは、第１レンズ群Ｇ１が１枚の正レンズ（第２レンズＬ１２）を有し、該正レンズのｄ線に対するアッベ数をνｄ１ｐとしたとき、以下の条件式
　　　νｄ１ｐ＜２９　…（３）
を満足している（表２２参照。以下、同様）。 In this zoom lens, when the first lens group G1 has one positive lens (second lens L12) and the Abbe number of the positive lens with respect to the d-line is νd1p, the following conditional expression νd1p <29. (3)
(See Table 22. The same applies hereinafter).
　また本ズームレンズは、第２レンズ群Ｇ２が１枚の負レンズ（第４レンズＬ２２）を有し、該負レンズのｄ線に対するアッベ数をνｄ２ｎとしたとき、以下の条件式
　　　νｄ２ｎ＜２９　…（４）
を満足している。 In this zoom lens, the second lens group G2 has one negative lens (fourth lens L22), and the Abbe number of the negative lens with respect to the d-line is νd2n, the following conditional expression νd2n <29. (4)
Is satisfied.
　さらに本ズームレンズは、第１レンズ群Ｇ１が実質的に、物体側より順に、負の屈折力を有する第１レンズＬ１１および正の屈折力を有する第２レンズＬ１２の２枚より構成され、該２枚のレンズの光軸Ｚ上での空気間隔をｄ２、広角端における全系の焦点距離をｆｗとしたとき、以下の条件式
　　　０．３１＜ｄ２／ｆｗ＜０．７０　…（５）
を満足している。 Further, in the present zoom lens, the first lens group G1 is composed of two lenses, a first lens L11 having a negative refractive power and a second lens L12 having a positive refractive power, in order from the object side. When the air interval on the optical axis Z of the two lenses is d2, and the focal length of the entire system at the wide angle end is fw, the following conditional expression 0.31 <d2 / fw <0.70 (5)
Is satisfied.
　また本ズームレンズは、広角端および望遠端の焦点距離をそれぞれｆｗ、ｆｔとしたとき、以下の条件式
　　　２．０＜ｆｔ／ｆｗ＜５．０　…（６）
を満足している。 In this zoom lens, when the focal lengths at the wide-angle end and the telephoto end are fw and ft, respectively, the following conditional expression 2.0 <ft / fw <5.0 (6)
Is satisfied.
　なお上記条件式（３）～（６）は、全て満足させる必要はなく、それらのうちのいくつかを満足するようにしてもよい。それらの条件式（３）、（４）、（５）および（６）で示した各条件のより望ましい範囲は下記の通りであり、
　　　νｄ１ｐ＜２６　…（３’）
　　　νｄ２ｎ＜２６　…（４’）
　　　０．３１＜ｄ２／ｆｗ＜０．６０　…（５’）
　　　２．３＜ｆｔ／ｆｗ＜５．０　…（６’）
本実施例では、これらの条件式も全て満足されている。 The conditional expressions (3) to (6) need not all be satisfied, and some of them may be satisfied. The more desirable ranges of the conditions shown in the conditional expressions (3), (4), (5) and (6) are as follows:
νd1p <26 (3 ′)
νd2n <26 (4 ′)
0.31 <d2 / fw <0.60 (5 ′)
2.3 <ft / fw <5.0 (6 ′)
In this embodiment, all of these conditional expressions are also satisfied.
　また本ズームレンズにおいては、無限遠から近距離へのフォーカシングに際して、第２レンズ群Ｇ２全体を光軸Ｚに沿って移動させる構成となっている。なお、第２レンズ群Ｇ２に配置された一部のレンズを光軸Ｚに沿って移動させる構成としても構わない。より具体的には、第５レンズＬ２３のみを光軸Ｚに沿って移動させる構成等が採用可能である。 The zoom lens has a configuration in which the entire second lens group G2 is moved along the optical axis Z during focusing from infinity to a short distance. It should be noted that some lenses arranged in the second lens group G2 may be moved along the optical axis Z. More specifically, a configuration in which only the fifth lens L23 is moved along the optical axis Z can be employed.
　さらに本ズームレンズは、第１レンズ群Ｇ１が１枚の負レンズ（第１レンズＬ１１）を有し、該負レンズのｄ線に対する屈折率およびアッベ数をそれぞれ、ｎｄ１ｎ、νｄ１ｎとしたとき、以下の条件式
　　　１．４８＜ｎｄ１ｎ＜１．５６　…（７）
　　　５０＜νｄ１ｎ＞６０　…（８）
を満足している。 Further, in this zoom lens, when the first lens group G1 has one negative lens (first lens L11) and the refractive index and Abbe number of the negative lens with respect to the d-line are nd1n and νd1n, respectively, Conditional expression of 1.48 <nd1n <1.56 (7)
50 <νd1n> 60 (8)
Is satisfied.
　また本ズームレンズは、第２レンズ群Ｇ２が２枚の正レンズ（第３レンズＬ２１および第５レンズＬ２３）を有し、該正レンズのｄ線に対する屈折率およびアッベ数をそれぞれ、ｎｄ２ｐ、νｄ２ｐしたとき、以下の条件式
　　　１．４８＜ｎｄ２ｐ＜１．５６　…（９）
　　　５０＜νｄ２ｐ＜６０　…（１０）
を満足している。 In this zoom lens, the second lens group G2 has two positive lenses (third lens L21 and fifth lens L23), and the refractive index and Abbe number of the positive lens with respect to the d-line are nd2p and νd2p, respectively. Then, the following conditional expression 1.48 <nd2p <1.56 (9)
50 <νd2p <60 (10)
Is satisfied.
　また本ズームレンズにおいては、第１レンズ群Ｇ１が物体側より順に、負の屈折力を有する第１レンズＬ１１、正の屈折力を有する第２レンズＬ１２から構成され、第１レンズＬ１１のｄ線に対する屈折率、アッベ数を各々ｎｄ１１、νｄ１１とし、第２レンズＬ１２のｄ線に対する屈折率、アッベ数を各々ｎｄ１２、νｄ１２としたとき、それらのレンズは下記条件
　　　１．４８＜ｎｄ１１＜１．６１　…（１１）
　　　５０＜νｄ１１　…（１２）
　　　１．５６＜ｎｄ１２＜１．６６　…（１３）
　　　νｄ１２＜３３　…（１４）
を満足するプラスチック材料から形成されている。 In this zoom lens, the first lens group G1 is composed of a first lens L11 having negative refractive power and a second lens L12 having positive refractive power in order from the object side. Where the refractive index and Abbe number for nd are nd11 and νd11, respectively, and the refractive index and Abbe number for the d-line of the second lens L12 are nd12 and νd12, respectively. ... (11)
50 <νd11 (12)
1.56 <nd12 <1.66 (13)
νd12 <33 (14)
It is formed from a plastic material that satisfies the requirements.
　なお上記条件式（１２）および（１４）が規定する条件内でより望ましい値の範囲はそれぞれ下記
　　　５２＜νｄ１１　…（１２’）
　　　νｄ１２＜２９　…（１４’）
の通りであるが、本実施例ではこれらの条件式（１２’）および（１４’）も満足されている。 The range of more desirable values within the conditions defined by the conditional expressions (12) and (14) is 52 <νd11 (12 ′)
νd12 <29 (14 ′)
However, in this embodiment, these conditional expressions (12 ′) and (14 ′) are also satisfied.
　また本ズームレンズにおいては、第２レンズ群Ｇ２が物体側より順に、正の屈折力を有する第３レンズＬ２１、負の屈折力を有する第４レンズＬ２２、正の屈折力を有する第５レンズＬ２３から構成され、第３レンズＬ２１のｄ線に対する屈折率、アッベ数を各々ｎｄ２１、νｄ２１とし、第４レンズＬ２２のｄ線に対する屈折率、アッベ数を各々ｎｄ２２、νｄ２２とし、第５レンズＬ２３のｄ線に対する屈折率、アッベ数を各々ｎｄ２３、νｄ２３としたとき、それらのレンズは下記条件
　　　１．４８＜ｎｄ２１＜１．６１　…（１５）
　　　５０＜νｄ２１　…（１６）
　　　１．５６＜ｎｄ２２＜１．６８　…（１７）
　　　νｄ２２＜３３　…（１８）
　　　１．４８＜ｎｄ２３＜１．６１　…（１９）
　　　５０＜νｄ２３　…（２０）
を満足するプラスチック材料から形成されている。なお上記条件式（１６）、（１８）および（２０）が規定する条件内でより望ましい値の範囲はそれぞれ下記
　　　５２＜νｄ２１　…（１６’）
　　　νｄ２２＜２９　…（１８’）
　　　５２＜νｄ２３　…（２０’）
の通りであるが、本実施例ではこれらの条件式（１６’）、（１８’）および（２０’）も満足されている。 In this zoom lens, the second lens group G2, in order from the object side, a third lens L21 having a positive refractive power, a fourth lens L22 having a negative refractive power, and a fifth lens L23 having a positive refractive power. The refractive index and Abbe number of the third lens L21 for the d-line are nd21 and νd21, respectively, and the refractive index and Abbe number of the fourth lens L22 for the d-line are nd22 and νd22, respectively, and d of the fifth lens L23. When the refractive index and Abbe number with respect to the line are nd23 and νd23, these lenses have the following conditions: 1.48 <nd21 <1.61 (15)
50 <νd21 (16)
1.56 <nd22 <1.68 (17)
νd22 <33 (18)
1.48 <nd23 <1.61 (19)
50 <νd23 (20)
It is formed from a plastic material that satisfies the requirements. The range of more desirable values within the conditions defined by the conditional expressions (16), (18) and (20) is 52 <νd21 (16 ′) below.
νd22 <29 (18 ′)
52 <νd23 (20 ′)
However, in this embodiment, these conditional expressions (16 ′), (18 ′), and (20 ′) are also satisfied.
　以下、上記各条件式で規定された構成による作用、効果について説明する。 Hereinafter, the operation and effect of the configuration defined by the above conditional expressions will be described.
　条件式（１）は、第２レンズ群Ｇ２の移動量と望遠端における全系の焦点距離との関係を規定しており、条件式の下限値以下になると、変倍比を大きくすることが困難になる。またその場合は、第２レンズ群Ｇ２のパワーを強くしなければならず、製造誤差や組立誤差の許容量が少なくなってしまうため好ましくない。さらにその場合は、プラスチックレンズのパワーが強くなり、温度による光学性能や特性の変化が大きくなるため、好ましくない。逆に、条件式の上限値以上になると、第２レンズ群Ｇ２の移動量が大きくなり、レンズ系が大型化するため好ましくない。条件式（１）を満足している場合は、以上の不具合を防止して、少ないレンズ枚数で３倍乃至４倍程度の変倍比を確保しつつ、各レンズのパワーを最適に設定することで良好な光学性能を実現可能となる。 Conditional expression (1) defines the relationship between the amount of movement of the second lens group G2 and the focal length of the entire system at the telephoto end. When the conditional expression (1) is below the lower limit of the conditional expression, the zoom ratio can be increased. It becomes difficult. In this case, it is not preferable because the power of the second lens group G2 must be increased, and an allowable amount of manufacturing error and assembly error is reduced. Further, in that case, the power of the plastic lens becomes strong, and the change in optical performance and characteristics due to temperature increases, which is not preferable. On the other hand, if the upper limit of the conditional expression is exceeded, the amount of movement of the second lens group G2 becomes large, and the lens system becomes large, which is not preferable. When the conditional expression (1) is satisfied, the above-mentioned problems are prevented, and the power of each lens is set optimally while securing a zoom ratio of about 3 to 4 times with a small number of lenses. With this, good optical performance can be realized.
　条件式（２）は、望遠端における全系の焦点距離と第１レンズ群Ｇ１の焦点距離の関係を規定しており、下限値以下になると、変倍時の移動量が大きくなり、レンズ系が大型化してしまうため好ましくない。逆に上限値以上になると、主に、広角端近傍での像面湾曲の補正が困難になる。また、プラスチックレンズのパワーが強くなり、温度による光学性能や特性の変化が大きくなるため、好ましくない。条件式（２）を満足している場合は、以上の不具合も防止できるので、上述の効果すなわち、少ないレンズ枚数で３倍乃至４倍程度の変倍比を確保しつつ、良好な光学性能を実現できるという効果をより顕著なものとすることができる。 Conditional expression (2) defines the relationship between the focal length of the entire system at the telephoto end and the focal length of the first lens group G1, and when it becomes less than the lower limit, the amount of movement during zooming increases, and the lens system Is unfavorable because it increases in size. On the other hand, when the upper limit value is exceeded, it becomes difficult to correct curvature of field mainly near the wide-angle end. Further, the power of the plastic lens becomes strong, and the optical performance and characteristics change with temperature, which is not preferable. When the conditional expression (2) is satisfied, the above-described problems can be prevented, so that the above-described effect, that is, good optical performance can be obtained while securing a zoom ratio of about 3 to 4 times with a small number of lenses. The effect of being realizable can be made more remarkable.
　条件式（３）は、第１レンズ群Ｇ１内に配置される正レンズ（第２レンズＬ１２）のアッベ数を規定しており、条件式の範囲を外れると、特に倍率色収差が大きくなるため、好ましくない。条件式（３）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (3) defines the Abbe number of the positive lens (second lens L12) disposed in the first lens group G1, and if the range of the conditional expression is outside the range, the chromatic aberration of magnification becomes particularly large. It is not preferable. When the conditional expression (3) is satisfied, the above problem can be prevented.
　条件式（４）は、第２レンズ群Ｇ２内に配置される負レンズ（第４レンズＬ２２）のアッベ数を規定しており、条件式の範囲を外れると、特に軸上色収差が大きくなるため、好ましくない。条件式（４）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (4) prescribes the Abbe number of the negative lens (fourth lens L22) disposed in the second lens group G2, and the axial chromatic aberration becomes particularly large if the conditional expression is outside the range. It is not preferable. When the conditional expression (4) is satisfied, the above problem can be prevented.
　条件式（５）は、第１レンズ群Ｇ１に配置される第１レンズＬ１１と第２レンズＬ１２の間隔と、広角端における全系の焦点距離との関係を規定しており、その下限値以下になると、コンパクト化には有利になるが、球面収差の補正が難しくなるため好ましくない。逆に上限値以上になると、第１レンズ群Ｇ１全体が大型化してしまうため、好ましくない。条件式（５）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (5) defines the relationship between the distance between the first lens L11 and the second lens L12 arranged in the first lens group G1 and the focal length of the entire system at the wide-angle end, and is below the lower limit value thereof. Then, it is advantageous for downsizing, but it is not preferable because correction of spherical aberration becomes difficult. On the other hand, if the upper limit value is exceeded, the entire first lens group G1 becomes large, which is not preferable. When the conditional expression (5) is satisfied, the above problem can be prevented.
　条件式（６）は、広角端および望遠端の各焦点距離の関係、つまり変倍比を規定しており、下限値以下になると、ズームレンズとしての有意性が小さくなってしまう。逆に上限値以上になると、レンズ系が大型化してしまう。また、このズームタイプにおいては、望遠端において明るさの低下が大きくなり過ぎてしまい、好ましくない。また、望遠端において、ある程度の明るさを確保しようとすれば、第２レンズ群Ｇ２への負担が大きくなり、少ないレンズ枚数での収差補正が困難になってしまう。条件式（６）を満足している場合は、上記の不具合を防止することができる。 Conditional expression (6) defines the relationship between the focal lengths at the wide-angle end and the telephoto end, that is, the zoom ratio, and if it is below the lower limit value, the significance as a zoom lens is reduced. On the other hand, if the upper limit is exceeded, the lens system becomes large. In addition, this zoom type is not preferable because the brightness decreases excessively at the telephoto end. Further, if it is attempted to secure a certain level of brightness at the telephoto end, the burden on the second lens group G2 increases, and it becomes difficult to correct aberrations with a small number of lenses. When the conditional expression (6) is satisfied, the above problem can be prevented.
　本ズームレンズでは、以上述べた条件式（３）、（４）、（５）および（６）が規定する範囲の中で特にそれぞれ前記条件式（３’）、（４’）、（５’）および（６’）が満足されているので、上記の効果がより顕著なものとなる。 In this zoom lens, the conditional expressions (3 ′), (4 ′), and (5 ′) are particularly preferable within the ranges defined by the conditional expressions (3), (4), (5), and (6) described above. ) And (6 ′) are satisfied, the above effect becomes more remarkable.
　また、第１レンズ群Ｇ１に配された負レンズ（第１レンズＬ１１）の屈折率ｎｄ１ｎが条件式（７）の下限値以下になると、レンズの曲率（近似曲率）が大きくなって像面湾曲および歪曲収差の補正が困難になる。逆に上限値以上になると、非点収差や倍率色収差の補正のバランスをとることが困難になり、好ましくない。本ズームレンズでは条件式（７）を満足しているので、上記の不具合を防止することができる。 Further, when the refractive index nd1n of the negative lens (first lens L11) arranged in the first lens group G1 is equal to or lower than the lower limit value of the conditional expression (7), the curvature of the lens (approximate curvature) increases and the curvature of field is increased. And it becomes difficult to correct distortion. On the other hand, if the value exceeds the upper limit, it is difficult to balance astigmatism and lateral chromatic aberration correction, which is not preferable. Since this zoom lens satisfies the conditional expression (7), the above-mentioned problem can be prevented.
　また、第１レンズ群Ｇ１に配された負レンズ（第１レンズＬ１１）のアッベ数νｄ１ｎが条件式（８）の範囲を外れると、特に広角端近傍での倍率色収差の補正が困難になるが、本ズームレンズは条件式（８）を満足しているので、この不具合を防止することができる。 If the Abbe number νd1n of the negative lens (first lens L11) arranged in the first lens group G1 is out of the range of the conditional expression (8), it is difficult to correct lateral chromatic aberration particularly near the wide-angle end. Since this zoom lens satisfies the conditional expression (8), this problem can be prevented.
　また、第２レンズ群Ｇ２に配された正レンズ（第３レンズＬ２１および第５レンズＬ２３）の屈折率ｎｄ２ｐが条件式（９）の下限値以下になると、レンズの曲率（近似曲率）が大きくなり、収差発生量が大きくなってしまう。逆に上限値以上になると、非点収差が大きくなるので好ましくない。本ズームレンズは、条件式（９）を満足しているので、上記の不具合を防止することができる。 Further, when the refractive index nd2p of the positive lens (the third lens L21 and the fifth lens L23) arranged in the second lens group G2 is equal to or lower than the lower limit value of the conditional expression (9), the lens curvature (approximate curvature) becomes large. As a result, the amount of aberration generated becomes large. On the other hand, when the value exceeds the upper limit, astigmatism increases, which is not preferable. Since this zoom lens satisfies the conditional expression (9), the above-described problem can be prevented.
　また、第２レンズ群Ｇ２に配された正レンズ（第３レンズＬ２１および第５レンズＬ２３）のアッベ数νｄ２ｐが条件式（１０）の範囲を外れると、軸上色収差の補正が困難になるが、本ズームレンズは条件式（１０）を満足しているので、この不具合を防止することができる。 Further, if the Abbe number νd2p of the positive lenses (the third lens L21 and the fifth lens L23) arranged in the second lens group G2 is out of the range of the conditional expression (10), it is difficult to correct axial chromatic aberration. Since this zoom lens satisfies the conditional expression (10), this problem can be prevented.
　また本ズームレンズでは、第１レンズ群Ｇ１が物体側より順に、負の屈折力を有する第１レンズＬ１１、正の屈折力を有する第２レンズＬ１２から構成された上で、前記条件式（１１）～（１４）を満足しているので、下記の効果を得ることができる。すなわち条件式（１１）および条件式（１３）はそれぞれ、第１レンズＬ１１の屈折率、第２レンズＬ１２の屈折率を規定しており、それらの条件式の下限値以下になると、収差の発生が大きくなってしまうとともに、レンズの曲率（近似曲率）が大きくなって、第１レンズ群Ｇ１が厚くなってしまうため好ましくない。また、低コスト化や軽量化等の目的によって、第１レンズ群Ｇ１に配置された２枚のレンズＬ１１およびＬ１２をプラスチックレンズで構成する場合、それらの条件式の上限値以上となるような材料で構成すると、非点収差や倍率色収差の補正のバランスをとることが困難になり、好ましくない。本ズームレンズは条件式（１１）および（１３）を満足しているので、以上の不具合を防止することができる。 In this zoom lens, the first lens group G1 includes, in order from the object side, the first lens L11 having a negative refractive power and the second lens L12 having a positive refractive power, and then the conditional expression (11 ) To (14) are satisfied, the following effects can be obtained. That is, conditional expression (11) and conditional expression (13) define the refractive index of the first lens L11 and the refractive index of the second lens L12, respectively. Is increased, the curvature of the lens (approximate curvature) is increased, and the first lens group G1 is thickened. In addition, when the two lenses L11 and L12 arranged in the first lens group G1 are made of plastic lenses for the purpose of cost reduction and weight reduction, a material that exceeds the upper limit value of these conditional expressions. This is not preferable because it is difficult to balance correction of astigmatism and lateral chromatic aberration. Since this zoom lens satisfies the conditional expressions (11) and (13), the above problems can be prevented.
　条件式（１２）および条件式（１４）はそれぞれ、第１レンズＬ１１のアッベ数、第２レンズＬ１２のアッベ数を規定しており、それらの条件式の範囲を外れると、第１レンズＬ１１と第２レンズＬ１２とのアッベ数の差が小さくなり、色収差の補正が困難になる。また、条件式（１２）あるいは（１４）の範囲を外れると、色収差補正のために、第１レンズ群Ｇ１に配置された他方のレンズ（条件式（１４）で第２レンズＬ１２のアッベ数を規定する場合は第１レンズＬ１１がこの「他方のレンズ」であり、条件式（１２）で第１レンズＬ１１のアッベ数を規定する場合は第２レンズＬ１２がこの「他方のレンズ」である）のパワーも強くする必要があり、特に、広角端において像面湾曲や歪曲収差の補正が困難になるため、好ましくない。本ズームレンズは条件式（１２）および（１４）を満足しているので、以上の不具合を防止することができる。 Conditional expression (12) and conditional expression (14) define the Abbe number of the first lens L11 and the Abbe number of the second lens L12, respectively. The difference in Abbe number from the second lens L12 becomes small, and correction of chromatic aberration becomes difficult. If the range of the conditional expression (12) or (14) is exceeded, the Abbe number of the second lens L12 in the other lens (conditional expression (14)) arranged in the first lens group G1 is corrected for chromatic aberration correction. The first lens L11 is this “other lens” when it is defined, and the second lens L12 is this “other lens” when the Abbe number of the first lens L11 is defined by the conditional expression (12)) Is also not preferable because it is difficult to correct curvature of field and distortion at the wide-angle end. Since this zoom lens satisfies the conditional expressions (12) and (14), the above problems can be prevented.
　本ズームレンズでは、条件式（１２）、（１４）の範囲の中で特にそれぞれ、条件式（１２’）、（１４’）が満足されているので、以上述べた効果がより顕著なものとなる。 In this zoom lens, conditional expressions (12 ′) and (14 ′) are satisfied particularly within the ranges of conditional expressions (12) and (14), respectively. Become.
　また本発明のズームレンズにおいて特に、第２レンズ群Ｇ２が物体側より順に、正の屈折力を有する第３レンズＬ２１、負の屈折力を有する第４レンズＬ２２、正の屈折力を有する第５レンズＬ２３より構成された上で、前記条件式（１５）～（２０）が満足されている場合は、像面湾曲や球面収差をバランス良く補正する上で有利となる。 In the zoom lens of the present invention, in particular, the second lens group G2, in order from the object side, a third lens L21 having a positive refractive power, a fourth lens L22 having a negative refractive power, and a fifth lens having a positive refractive power. When the conditional expressions (15) to (20) are satisfied after the lens L23 is configured, it is advantageous in correcting field curvature and spherical aberration in a well-balanced manner.
　本ズームレンズでは、条件式（１６）、（１８）、（２０）の範囲の中でも特にそれぞれ、条件式（１６’）、（１８’）、（２０’）が満足されているので、上記効果がより顕著なものとなる。 In the present zoom lens, the conditional expressions (16 ′), (18 ′), and (20 ′) are satisfied particularly within the ranges of the conditional expressions (16), (18), and (20). Becomes more prominent.
　また本ズームレンズでは、無限遠から近距離へのフォーカシングに際して、第２レンズ群Ｇ２全体を光軸Ｚに沿って移動させる構成となっているので、下記の効果を得ることができる。すなわち、第１レンズ群Ｇ１全体を繰り出してフォーカスする構成を採用した場合は、第１レンズ群Ｇ１の有効径が大きくなったり、外径の大きなレンズを動かす必要が生じたりするが、第２レンズ群Ｇ２全体を移動させる場合は、そのような問題を回避することが可能になる。 In addition, the zoom lens has a configuration in which the entire second lens group G2 is moved along the optical axis Z during focusing from infinity to a short distance, so that the following effects can be obtained. That is, when the configuration in which the entire first lens group G1 is extended and focused is adopted, the effective diameter of the first lens group G1 or the lens having a large outer diameter needs to be moved. Such a problem can be avoided when moving the entire group G2.
　なお、第２レンズ群Ｇ２全体ではなく、その一部のレンズ、例えば正の屈折力を有する第５レンズＬ２３のみを光軸Ｚに沿って移動させる構成とした場合も、上記の効果をより顕著なものとして得ることができる。 Note that the above-described effect is more conspicuous even when the configuration is such that only a part of the second lens group G2 is moved along the optical axis Z, for example, only a part of the second lens group G2, for example, the fifth lens L23 having a positive refractive power. Can be obtained.
　なお図１には、レンズ系と結像面との間に光学部材ＰＰを配置した例を示したが、ローパスフィルタや特定の波長域をカットするような各種フィルタ等を配置する代わりに、各レンズの間にこれらの各種フィルタを配置してもよく、あるいは、いずれかのレンズのレンズ面に、各種フィルタと同様の作用を有するコートを施してもよい。 FIG. 1 shows an example in which the optical member PP is disposed between the lens system and the imaging plane, but instead of disposing a low-pass filter, various filters that cut a specific wavelength range, etc. These various filters may be disposed between the lenses, or a coating having the same action as the various filters may be applied to the lens surface of any lens.
　次に、本発明のズームレンズの数値実施例について説明する。実施例１～７のズームレンズのレンズ断面図はそれぞれ図１～７に示したものである。 Next, numerical examples of the zoom lens according to the present invention will be described. Lens sectional views of the zoom lenses of Examples 1 to 7 are shown in FIGS. 1 to 7, respectively.
　そして、実施例１のズームレンズの基本レンズデータを表１に、ズームに関するデータを表２に、非球面データを表３に示す。同様に、実施例２～７のズームレンズの基本レンズデータ、ズームに関するデータ、非球面データを表４～表２１に示す。以下では、表中の記号の意味について、実施例１のものを例に挙げて説明するが、実施例２～７のものについても基本的に同様である。 Table 1 shows basic lens data of the zoom lens of Example 1, Table 2 shows data relating to zooming, and Table 3 shows aspherical data. Similarly, Tables 4 to 21 show basic lens data, zoom-related data, and aspherical data of the zoom lenses of Examples 2 to 7, respectively. In the following, the meaning of the symbols in the table will be described using the example 1 as an example, but the same applies to the examples 2 to 7.
　表１の基本レンズデータにおいて、Ｓｉの欄には最も物体側の構成要素の物体側の面を１番目として像側に向かうに従い順次増加するｉ番目（ｉ＝１、２、３、…）の面番号を示し、Ｒｉの欄にはｉ番目の面の曲率半径を示し、Ｄｉの欄にはｉ番目の面とｉ＋１番目の面との光軸Ｚ上の面間隔を示している。なお、曲率半径の符号は、面形状が物体側に凸の場合を正、像側に凸の場合を負としている。 In the basic lens data of Table 1, in the column of Si, the i-th (i = 1, 2, 3,...) That sequentially increases toward the image side with the object-side surface of the most object-side component as the first. The surface number is indicated, the Ri column indicates the radius of curvature of the i-th surface, and the Di column indicates the surface interval on the optical axis Z between the i-th surface and the i + 1-th surface. The sign of the radius of curvature is positive when the surface shape is convex on the object side and negative when the surface shape is convex on the image side.
　また、基本レンズデータにおいて、Ｎｄｊの欄には最も物体側のレンズを１番目として像側に向かうに従い順次増加するｊ番目（ｊ＝１、２、３、…）の構成要素のｄ線（波長５８７．６ｎｍ）に対する屈折率を示し、νｄｊの欄にはｊ番目の構成要素のｄ線に対するアッベ数を示している。なお、基本レンズデータには、開口絞りＳｔも含めて示しており、開口絞りＳｔに相当する面の曲率半径の欄には、∞（開口絞り）と記載している。 In the basic lens data, in the column Ndj, the d-line (wavelength) of the j-th component (j = 1, 2, 3,...) That increases sequentially toward the image side with the most object-side lens as the first lens. 587.6 nm), and the column νdj indicates the Abbe number of the j-th component with respect to the d-line. The basic lens data also includes the aperture stop St, and ∞ (aperture stop) is described in the column of the radius of curvature of the surface corresponding to the aperture stop St.
　表１の基本レンズデータにおけるＤ４、Ｄ１１は、変倍時に変化する面間隔である。Ｄ４は第１レンズ群Ｇ１と第２レンズ群Ｇ２との間隔であり、Ｄ１１は第２レンズ群Ｇ２と光学部材ＰＰとの間隔である。ただし実施例２、７では、上記Ｄ１１の代わりにＤ９を用いている。 D4 and D11 in the basic lens data in Table 1 are surface intervals that change during zooming. D4 is the distance between the first lens group G1 and the second lens group G2, and D11 is the distance between the second lens group G2 and the optical member PP. However, in Examples 2 and 7, D9 is used instead of D11.
　表２のズームに関するデータには、広角端、望遠端それぞれにおける、全系の焦点距離（ｆ）、Ｆ値（Ｆｎｏ．）、全画角（２ω）、変倍時に変化する各面間隔の値を示している。 The zoom-related data in Table 2 includes the focal length (f), F value (Fno.), Total angle of view (2ω), and the distance between each surface that changes during zooming at the wide-angle end and the telephoto end. Is shown.
　表１のレンズデータでは、非球面の面番号に＊印を付しており、非球面の曲率半径として近軸の曲率半径の数値を示している。表３の非球面データには、非球面の面番号と、各非球面に関する非球面係数を示す。表３の非球面データの数値の「Ｅ－ｎ」（ｎ：整数）は、「×１０－ｎ」を意味する。なお、非球面係数は、下記非球面式における各係数ＫＡ、ＲＡｍ（ｍ＝３、４、５、…１２）の値である。 In the lens data in Table 1, the surface number of the aspheric surface is marked with *, and the paraxial radius of curvature is shown as the radius of curvature of the aspheric surface. The aspheric data in Table 3 shows the surface number of the aspheric surface and the aspheric coefficient for each aspheric surface. The numerical value “E−n” (n: integer) of the aspherical data in Table 3 means “× 10− n ”. The aspheric coefficient is a value of each coefficient KA, RAm (m = 3, 4, 5,... 12) in the following aspheric expression.
　　Ｚｄ＝Ｃ・ｈ２／｛１＋（１－ＫＡ・Ｃ２・ｈ２）１/２｝＋ΣＲＡｍ・ｈｍ
ただし、
Ｚｄ：非球面深さ（高さｈの非球面上の点から、非球面頂点が接する光軸に垂直な平面に下ろした垂線の長さ）
ｈ：高さ（光軸からのレンズ面までの距離）
Ｃ：近軸曲率半径の逆数
ＫＡ、ＲＡｍ：非球面係数（ｍ＝３、４、５、…１２）
　以下に記載する表では、所定の桁で丸めた数値を記載している。また、以下に記載する表のデータにおいて、角度の単位としては度を用い、長さの単位としてはｍｍを用いているが、光学系は比例拡大又は比例縮小して使用することが可能であるので、他の適当な単位を用いることもできる。
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000012
Figure JPOXMLDOC01-appb-T000013
Figure JPOXMLDOC01-appb-T000014
Figure JPOXMLDOC01-appb-T000015
Figure JPOXMLDOC01-appb-T000016
Figure JPOXMLDOC01-appb-T000017
Figure JPOXMLDOC01-appb-T000018
Figure JPOXMLDOC01-appb-T000019
Figure JPOXMLDOC01-appb-T000020
Figure JPOXMLDOC01-appb-T000021
 Zd = C · h 2 / {1+ (1−KA · C 2 · h 2 ) 1/2 } + ΣRAm · h m
However,
Zd: Depth of aspheric surface (length of a perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis where the aspherical vertex contacts)
h: Height (distance from the optical axis to the lens surface)
C: Reciprocal number of paraxial radius of curvature KA, RAm: aspheric coefficient (m = 3, 4, 5,... 12)
In the table described below, values rounded to a predetermined digit are shown. Moreover, in the data of the table | surface described below, although the degree is used as a unit of angle and mm is used as a unit of length, an optical system can be used by proportional expansion or proportional reduction. Thus, other suitable units can be used.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000012
Figure JPOXMLDOC01-appb-T000013
Figure JPOXMLDOC01-appb-T000014
Figure JPOXMLDOC01-appb-T000015
Figure JPOXMLDOC01-appb-T000016
Figure JPOXMLDOC01-appb-T000017
Figure JPOXMLDOC01-appb-T000018
Figure JPOXMLDOC01-appb-T000019
Figure JPOXMLDOC01-appb-T000020
Figure JPOXMLDOC01-appb-T000021
　また表２２に、実施例１～７のズームレンズの条件式（１）～（２０）に対応する値を示す。この表２２の値はｄ線に関するものである。
Figure JPOXMLDOC01-appb-T000022
 Table 22 shows values corresponding to the conditional expressions (1) to (20) of the zoom lenses of Examples 1 to 7. The values in Table 22 relate to the d line.
Figure JPOXMLDOC01-appb-T000022
　ここで、実施例１のズームレンズの広角端における球面収差、非点収差、ディストーション（歪曲収差）、倍率色収差（倍率の色収差）をそれぞれ図８（Ａ）～図８（Ｄ）に示し、望遠端における球面収差、非点収差、ディストーション（歪曲収差）、倍率色収差（倍率の色収差）をそれぞれ図８（Ｅ）～図８（Ｈ）に示す。 Here, spherical aberration, astigmatism, distortion (distortion aberration) and lateral chromatic aberration (chromatic aberration of magnification) at the wide-angle end of the zoom lens of Example 1 are shown in FIGS. 8A to 8D, respectively. FIGS. 8E to 8H show spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration (chromatic aberration of magnification) at the edges, respectively.
　各収差図はｄ線（波長５８７．６ｎｍ）を基準としたものであるが、球面収差図では波長４６０．０ｎｍおよび６１５．０ｎｍに関する収差も示し、倍率色収差図では波長４６０．０ｎｍおよび６１５．０ｎｍに関する収差を示す。非点収差図では、サジタル方向については実線で、タンジェンシャル方向については点線で示している。球面収差図のＦｎｏ．はＦ値を意味し、その他の収差図のωは半画角を意味する。 Each aberration diagram is based on the d-line (wavelength 587.6 nm), but the spherical aberration diagram also shows aberrations relating to wavelengths 460.0 nm and 615.0 nm, and the lateral chromatic aberration diagram shows wavelengths 460.0 nm and 615.0 nm. The aberration about is shown. In the astigmatism diagram, the sagittal direction is indicated by a solid line, and the tangential direction is indicated by a dotted line. Fno. Of spherical aberration diagram. Means F value, and ω in other aberration diagrams means half angle of view.
　同様に、実施例２のズームレンズの広角端、望遠端における各収差図を図９（Ａ）～図９（Ｈ）に示し、以下全く同様にして実施例３～７の各収差図をそれぞれ図１０～図１４に示す。 Similarly, the aberration diagrams at the wide-angle end and the telephoto end of the zoom lens of Example 2 are shown in FIGS. 9A to 9H, and the aberration diagrams of Examples 3 to 7 are respectively the same in the same manner. It is shown in FIGS.
　次に、本発明の実施形態にかかる撮像装置について説明する。図１５に、本発明の実施形態の撮像装置の一例として、本発明の実施形態のズームレンズ１を用いた撮像装置１０の概略構成図を示す。撮像装置としては、例えば、監視カメラ、ビデオカメラ、電子スチルカメラ等を挙げることができる。 Next, an imaging apparatus according to an embodiment of the present invention will be described. FIG. 15 shows a schematic configuration diagram of an imaging apparatus 10 using the zoom lens 1 of the embodiment of the present invention as an example of the imaging apparatus of the embodiment of the present invention. Examples of the imaging device include a surveillance camera, a video camera, and an electronic still camera.
　図１５に示す撮像装置１０は、ズームレンズ１と、ズームレンズ１の像側に配置されて、ズームレンズ１により結像された被写体の像を撮像する撮像素子２と、撮像素子２からの出力信号を演算処理する信号処理部４と、ズームレンズ１の変倍を行うための変倍制御部５と、フォーカス調整を行うためのフォーカス制御部６とを備えている。なお、ズームレンズ１と撮像素子２との間に、適宜フィルタ等が配設されてもよい。 An image pickup apparatus 10 shown in FIG. 15 is arranged on the zoom lens 1, the image side of the zoom lens 1, an image pickup device 2 that picks up an image of a subject imaged by the zoom lens 1, and an output from the image pickup device 2. A signal processing unit 4 that performs signal processing, a zooming control unit 5 for zooming the zoom lens 1, and a focus control unit 6 for performing focus adjustment are provided. A filter or the like may be appropriately disposed between the zoom lens 1 and the image sensor 2.
　ズームレンズ１は、負の屈折力を有して、広角端から望遠端に変倍する際に像面側に凸状の軌跡を描くように移動する第１レンズ群Ｇ１と、正の屈折力を有して、広角端から望遠端に変倍する際に物体側に単調移動する第２レンズ群Ｇ２と、第２レンズ群Ｇ２と一体で移動するように構成された開口絞りＳｔとを有している。なお、図１５では各レンズ群を概略的に示している。 The zoom lens 1 has a negative refractive power, a first lens group G1 that moves so as to draw a convex locus on the image plane side when zooming from the wide angle end to the telephoto end, and a positive refractive power. And a second lens group G2 that moves monotonically toward the object side when zooming from the wide-angle end to the telephoto end, and an aperture stop St that is configured to move integrally with the second lens group G2. is doing. FIG. 15 schematically shows each lens group.
　撮像素子２は、ズームレンズ１により形成される光学像を撮像して電気信号を出力するものであり、その撮像面はズームレンズ１の像面に一致するように配置されている。撮像素子２としては例えばＣＣＤやＣＭＯＳ等からなるものを用いることができる。 The image pickup device 2 picks up an optical image formed by the zoom lens 1 and outputs an electric signal. As the image pickup element 2, for example, a CCD or CMOS can be used.
　なお、図１５では図示していないが、撮像装置１０は、例えば第２レンズ群Ｇ２の一部を構成する正の屈折力を有するレンズを光軸Ｚに垂直な方向に移動させて、振動や手振れ時の撮影画像のぶれを補正するぶれ補正機構をさらに備えるようにしてもよい。 Although not shown in FIG. 15, the imaging device 10 moves a lens having a positive refractive power that constitutes a part of the second lens group G2 in a direction perpendicular to the optical axis Z, for example. You may make it further provide the blurring correction mechanism which correct | amends the blurring of the picked-up image at the time of camera shake.
　以上、実施形態および実施例を挙げて本発明を説明したが、本発明は上記実施形態および実施例に限定されるものではなく、種々の変形が可能である。例えば、各レンズ成分の曲率半径、面間隔、屈折率、アッベ数、非球面係数等の値は、上記各数値実施例で示した値に限定されず、他の値をとり得るものである。 Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the values of the radius of curvature, the surface interval, the refractive index, the Abbe number, the aspherical coefficient, etc. of each lens component are not limited to the values shown in the above numerical examples, and can take other values.

Claims (13)

  1. 　実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて、
    　前記第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、
    　広角端から望遠端に変倍するときの第２レンズ群の移動量をＭ２、望遠端における全系の焦点距離をｆｔとしたとき、以下の条件式を満足することを特徴とするズームレンズ。
    　　　０．４５＜Ｍ２／ｆｔ＜０．８　…（１）     The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming. In zoom lenses where
    Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses,
    A zoom lens that satisfies the following conditional expression, where M2 is the amount of movement of the second lens unit when zooming from the wide-angle end to the telephoto end, and ft is the focal length of the entire system at the telephoto end.
    0.45 <M2 / ft <0.8 (1)
  2. 　望遠端における全系の焦点距離をｆｔ、第１レンズ群の焦点距離をｆ１としたとき、以下の条件式を満足することを特徴とする請求項１に記載のズームレンズ。
    　　　１．５＜｜ｆｔ／ｆ１｜＜２．３　…（２）     2. The zoom lens according to claim 1, wherein the following conditional expression is satisfied, where ft is the focal length of the entire system at the telephoto end, and f <b> 1 is the focal length of the first lens unit.
    1.5 <| ft / f1 | <2.3 (2)
  3. 　実質的に、物体側より順に、負の屈折力を有する第１レンズ群と、正の屈折力を有する第２レンズ群とからなり、変倍に際して前記第１レンズ群と第２レンズ群の間隔が変化するズームレンズにおいて、
    　前記第１レンズ群および第２レンズ群が、それぞれ、全てプラスチックレンズを適用して、少なくとも２枚のレンズから構成され、
    　望遠端における全系の焦点距離をｆｔ、第１レンズ群の焦点距離をｆ１としたとき、以下の条件式を満足することを特徴とするズームレンズ。
    　　　１．５＜｜ｆｔ／ｆ１｜＜２．３　…（２）     The first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the object side, and a distance between the first lens group and the second lens group at the time of zooming. In zoom lenses where
    Each of the first lens group and the second lens group is composed of at least two lenses by applying all plastic lenses,
    A zoom lens that satisfies the following conditional expression, where ft is the focal length of the entire system at the telephoto end, and f1 is the focal length of the first lens unit.
    1.5 <| ft / f1 | <2.3 (2)
  4. 　前記第１レンズ群が少なくとも１枚の正レンズを有し、該正レンズのｄ線に対するアッベ数をνｄ１ｐとしたとき、以下の条件式を満足することを特徴とする請求項１から３のいずれか１項に記載のズームレンズ。
    　　　νｄ１ｐ＜２９　…（３）     4. The system according to claim 1, wherein the first lens group includes at least one positive lens, and the following conditional expression is satisfied when the Abbe number of the positive lens with respect to the d-line is νd1p. The zoom lens according to claim 1.
    νd1p <29 (3)
  5. 　以下の条件式を満足することを特徴とする請求項４に記載のズームレンズ。
    　　　νｄ１ｐ＜２６　…（３’）　　     The zoom lens according to claim 4, wherein the following conditional expression is satisfied.
    νd1p <26 (3 ′)
  6. 　前記第２レンズ群が少なくとも１枚の負レンズを有し、該負レンズのｄ線に対するアッベ数をνｄ２ｎとしたとき、以下の条件式を満足することを特徴とする請求項１から５のいずれか１項に記載のズームレンズ。
    　　　νｄ２ｎ＜２９　…（４）     6. The system according to claim 1, wherein the second lens group includes at least one negative lens, and the following conditional expression is satisfied when the Abbe number of the negative lens with respect to the d-line is νd2n. The zoom lens according to claim 1.
    νd2n <29 (4)
  7. 　以下の条件式を満足することを特徴とする請求項６に記載のズームレンズ。
    　　　νｄ２ｎ＜２６　…（４’）     The zoom lens according to claim 6, wherein the following conditional expression is satisfied.
    νd2n <26 (4 ′)
  8. 　前記第１レンズ群が実質的に、物体側より順に、負の屈折力を有する第１レンズおよび正の屈折力を有する第２レンズの２枚より構成され、
    　該２枚のレンズの光軸上での空気間隔をｄ２、広角端における全系の焦点距離をｆｗとしたとき、以下の条件式を満足することを特徴とする請求項１から７のいずれか１項に記載のズームレンズ。
    　　　０．３１＜ｄ２／ｆｗ＜０．７０　…（５）     The first lens group is substantially composed of two lenses, a first lens having a negative refractive power and a second lens having a positive refractive power, in order from the object side.
    The following conditional expression is satisfied, where d2 is an air interval on the optical axis of the two lenses, and fw is a focal length of the entire system at the wide angle end. The zoom lens according to item 1.
    0.31 <d2 / fw <0.70 (5)
  9. 　以下の条件式を満足することを特徴とする請求項８に記載のズームレンズ。
    　　　０．３１＜ｄ２／ｆｗ＜０．６０　…（５’）     The zoom lens according to claim 8, wherein the following conditional expression is satisfied.
    0.31 <d2 / fw <0.60 (5 ′)
  10. 　広角端および望遠端の焦点距離をそれぞれｆｗ、ｆｔとしたとき、以下の条件式を満足することを特徴とする請求項１から９のいずれか１項に記載のズームレンズ。
    　　　２．０＜ｆｔ／ｆｗ＜５．０　…（６）     10. The zoom lens according to claim 1, wherein the following conditional expressions are satisfied when the focal lengths at the wide-angle end and the telephoto end are fw and ft, respectively.
    2.0 <ft / fw <5.0 (6)
  11. 　以下の条件式を満足することを特徴とする請求項１０に記載のズームレンズ。
    　　　２．３＜ｆｔ／ｆｗ＜５．０　…（６’）     The zoom lens according to claim 10, wherein the following conditional expression is satisfied.
    2.3 <ft / fw <5.0 (6 ′)
  12. 　前記第１レンズ群が２枚以下のレンズから構成され、前記第２レンズ群が３枚以下のレンズから構成されていることを特徴とする請求項１から１１のいずれか１項に記載のズームレンズ。 The zoom according to any one of claims 1 to 11, wherein the first lens group includes two or less lenses, and the second lens group includes three or less lenses. lens.
  13. 　請求項１から１２のいずれか１項に記載のズームレンズを備えたことを特徴とする撮像装置。 An imaging apparatus comprising the zoom lens according to any one of claims 1 to 12.
PCT/JP2012/004058 2011-06-24 2012-06-22 Zoom lens and imaging device WO2012176470A1 (en)

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Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01210914A (en) * 1988-02-19 1989-08-24 Olympus Optical Co Ltd Variable power lens
JPH02109009A (en) * 1988-10-18 1990-04-20 Nikon Corp Kepler-type zoom finder optical system
JPH0446310A (en) * 1990-06-13 1992-02-17 Minolta Camera Co Ltd Compact zoom lens
JPH0446308A (en) * 1990-06-14 1992-02-17 Minolta Camera Co Ltd Compact zoom lens
JPH0456814A (en) * 1990-06-22 1992-02-24 Minolta Camera Co Ltd Compact zoom lens
JPH0467113A (en) * 1990-07-06 1992-03-03 Minolta Camera Co Ltd Compact zoom lens
JPH05281470A (en) * 1992-03-30 1993-10-29 Olympus Optical Co Ltd Small-sized two-group zoom lens
JP2002169089A (en) * 2001-12-05 2002-06-14 Olympus Optical Co Ltd Small-seized two-group zoom lens
JP2004264638A (en) * 2003-03-03 2004-09-24 Fuji Photo Optical Co Ltd Two-group zoom lens
JP2005173542A (en) * 2003-11-18 2005-06-30 Nagano Kogaku Kenkyusho:Kk Zoom lens
JP2005208566A (en) * 2003-12-22 2005-08-04 Sony Corp Zoom lens and imaging apparatus
JP2005275175A (en) * 2004-03-25 2005-10-06 Miyota Kk Small zoom lens

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01210914A (en) * 1988-02-19 1989-08-24 Olympus Optical Co Ltd Variable power lens
JPH02109009A (en) * 1988-10-18 1990-04-20 Nikon Corp Kepler-type zoom finder optical system
JPH0446310A (en) * 1990-06-13 1992-02-17 Minolta Camera Co Ltd Compact zoom lens
JPH0446308A (en) * 1990-06-14 1992-02-17 Minolta Camera Co Ltd Compact zoom lens
JPH0456814A (en) * 1990-06-22 1992-02-24 Minolta Camera Co Ltd Compact zoom lens
JPH0467113A (en) * 1990-07-06 1992-03-03 Minolta Camera Co Ltd Compact zoom lens
JPH05281470A (en) * 1992-03-30 1993-10-29 Olympus Optical Co Ltd Small-sized two-group zoom lens
JP2002169089A (en) * 2001-12-05 2002-06-14 Olympus Optical Co Ltd Small-seized two-group zoom lens
JP2004264638A (en) * 2003-03-03 2004-09-24 Fuji Photo Optical Co Ltd Two-group zoom lens
JP2005173542A (en) * 2003-11-18 2005-06-30 Nagano Kogaku Kenkyusho:Kk Zoom lens
JP2005208566A (en) * 2003-12-22 2005-08-04 Sony Corp Zoom lens and imaging apparatus
JP2005275175A (en) * 2004-03-25 2005-10-06 Miyota Kk Small zoom lens

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