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WO2012176470A1 - Objectif à focale variable et dispositif d'imagerie - Google Patents

Objectif à focale variable et dispositif d'imagerie 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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English (en)
Japanese (ja)
Inventor
大樹 河村
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Fujifilm Corp
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Fujifilm Corp
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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.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)

Abstract

La présente invention a pour objet un objectif à focale variable plus économique dont les performances optiques sont satisfaisantes. Un objectif à focale variable d'après la présente invention est essentiellement constitué, dans l'ordre depuis le côté objet, d'un premier groupe de lentilles (G1) ayant une puissance réfractive négative et d'un second groupe de lentilles (G2) ayant une puissance réfractive positive. Une modification du grossissement entraîne une modification de l'espace entre le premier groupe de lentilles (G1) et le second groupe de lentilles (G2). Toutes les lentilles des premier (G1) et second (G2) groupes de lentilles sont en plastique. Les deux groupes sont constitués d'au moins deux lentilles (le premier groupe de lentilles (G1) comportant les lentilles (L11, L12) et le second groupe de lentilles comportant les lentilles (L21, L22, L23)). De plus, soit M2 la quantité de déplacement du second groupe de lentilles (G2) lorsqu'on modifie le grossissement depuis le côté grand-angle vers le côté téléobjectif et ft la distance focale de l'ensemble du système au niveau du côté téléobjectif, l'expression conditionnelle suivante est satisfaite : 0,45 < M2/ft < 0,8.
PCT/JP2012/004058 2011-06-24 2012-06-22 Objectif à focale variable et dispositif d'imagerie Ceased WO2012176470A1 (fr)

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Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01210914A (ja) * 1988-02-19 1989-08-24 Olympus Optical Co Ltd 変倍レンズ
JPH02109009A (ja) * 1988-10-18 1990-04-20 Nikon Corp ケプラー式ズームファインダー光学系
JPH0446308A (ja) * 1990-06-14 1992-02-17 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0446310A (ja) * 1990-06-13 1992-02-17 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0456814A (ja) * 1990-06-22 1992-02-24 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0467113A (ja) * 1990-07-06 1992-03-03 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH05281470A (ja) * 1992-03-30 1993-10-29 Olympus Optical Co Ltd 小型の２群ズームレンズ
JP2002169089A (ja) * 2001-12-05 2002-06-14 Olympus Optical Co Ltd 小型の２群ズームレンズ
JP2004264638A (ja) * 2003-03-03 2004-09-24 Fuji Photo Optical Co Ltd ２群ズームレンズ
JP2005173542A (ja) * 2003-11-18 2005-06-30 Nagano Kogaku Kenkyusho:Kk ズームレンズ
JP2005208566A (ja) * 2003-12-22 2005-08-04 Sony Corp ズームレンズ及び撮像装置
JP2005275175A (ja) * 2004-03-25 2005-10-06 Miyota Kk 小型ズームレンズ

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01210914A (ja) * 1988-02-19 1989-08-24 Olympus Optical Co Ltd 変倍レンズ
JPH02109009A (ja) * 1988-10-18 1990-04-20 Nikon Corp ケプラー式ズームファインダー光学系
JPH0446310A (ja) * 1990-06-13 1992-02-17 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0446308A (ja) * 1990-06-14 1992-02-17 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0456814A (ja) * 1990-06-22 1992-02-24 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH0467113A (ja) * 1990-07-06 1992-03-03 Minolta Camera Co Ltd コンパクトなズームレンズ
JPH05281470A (ja) * 1992-03-30 1993-10-29 Olympus Optical Co Ltd 小型の２群ズームレンズ
JP2002169089A (ja) * 2001-12-05 2002-06-14 Olympus Optical Co Ltd 小型の２群ズームレンズ
JP2004264638A (ja) * 2003-03-03 2004-09-24 Fuji Photo Optical Co Ltd ２群ズームレンズ
JP2005173542A (ja) * 2003-11-18 2005-06-30 Nagano Kogaku Kenkyusho:Kk ズームレンズ
JP2005208566A (ja) * 2003-12-22 2005-08-04 Sony Corp ズームレンズ及び撮像装置
JP2005275175A (ja) * 2004-03-25 2005-10-06 Miyota Kk 小型ズームレンズ

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