JP2010197860A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide-angle and high variable magnification zoom lens with a simple configuration, while maintaining excellent optical performance and reducing the size of an optical system. <P>SOLUTION: The zoom lens includes: a first lens group G<SB>11</SB>having positive refractive power; a second lens group G<SB>12</SB>having negative refractive power; a third lens group G<SB>13</SB>having positive refractive power; a fourth lens group G<SB>14</SB>having negative refractive power; and a fifth lens group G<SB>15</SB>having positive refractive power, which are arranged in order from the object side. The first lens group G<SB>11</SB>includes: a negative lens L<SB>111</SB>, a positive lens L<SB>112</SB>, a positive lens L<SB>113</SB>and a positive lens L<SB>114</SB>, which are arranged in order from the object side. The negative lens L<SB>111</SB>and the positive lens L<SB>112</SB>are cemented to each other. A predetermined condition is satisfied, to attain a compact, wide-angle, and high variable magnification zoom lens while maintaining high optical performance that effectively corrects aberrations over the whole variable magnification range. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a compact, lightweight, high-magnification zoom lens that is optimal for mounting on electronic imaging devices such as video cameras and surveillance cameras.

  In recent years, various electronic imaging devices such as video cameras and surveillance cameras have become widespread. Many of such electronic imaging apparatuses are equipped with a zoom lens as a photographing lens. With the recent miniaturization of electronic imaging devices, zoom lenses mounted on electronic imaging devices are also required to be further miniaturized. In addition, as the demand for higher zooming of electronic imaging devices becomes stronger, further zooming of zoom lenses that can achieve this is expected.

  A zoom lens having a four-group configuration is well known as a zoom lens capable of high zooming. For example, in a zoom lens having a four-group configuration in which lens groups having positive, negative, positive and positive refractive powers are arranged in order from the object side, zooming is performed by moving the second group, and the fourth group is moved. Focusing can be performed. If the zoom lens having such a configuration realizes a magnification change of about 25 times, since there are two movable groups, the structure of the lens barrel can be simplified and the overall length of the optical system can be shortened. it can.

  However, in recent years, there has been a demand for a zoom lens that can further increase the magnification. Therefore, when an even higher zoom ratio is realized with a zoom lens having a four-group configuration, the movement amount of the lens group for zooming increases, so that the entire length of the optical system becomes longer and the outer diameter of the lens also increases. In addition, since the amount of movement of the lens group for performing focusing increases, the aberration variation becomes large. As described above, in the zoom lens having the four-group configuration, it is difficult to realize high zooming while maintaining the downsizing of the optical system and the optical performance.

  Therefore, in order to solve such a problem, a zoom lens having a five-group configuration has been proposed. In such a zoom lens having a five-group configuration, the first, third, and fifth groups are fixed, the zoom is performed by moving the second group in one direction, and the zoom is performed by moving the fourth group. It is common to perform correction and focusing of image plane fluctuations accompanying the above (for example, see Patent Documents 1 to 4).

  For example, in the zoom lens described in Patent Document 1, a lens group having positive, negative, positive and negative refractive powers is arranged in order from the object side, the field angle is 71 °, and the zoom ratio is about 20 times. In the zoom lens described in Patent Document 2, a lens group having positive, negative, positive and negative refractive powers is arranged in order from the object side, the angle of view is 63 °, and the zoom ratio is 20 to 30 times, which is a higher zoom ratio. It is possible. In the zoom lens described in Patent Document 3, a lens group having positive, negative, positive and negative refractive powers is arranged in order from the object side, the angle of view is 70.9 °, and the zoom ratio is about 35 times. Yes. In the zoom lens described in Patent Document 4, a lens group having positive, negative, positive and negative refractive powers is arranged in order from the object side, the angle of view is 70 °, and the zoom ratio is 50 times. Double is possible.

Japanese Patent No. 3453007 JP 2000-180722 A JP 2007-178598 A Japanese Patent Laid-Open No. 2000-23310

  However, in the zoom lens described in each of the above-mentioned patent documents, if the angle of view is to be made larger than 60 °, the front lens diameter increases, and accordingly, the entire optical system also increases. Further, when the zoom ratio and resolution are increased, not only the total length of the optical system increases, but also the occurrence of chromatic aberration at the telephoto end becomes remarkable, and sufficient resolution cannot be obtained. In particular, in a large-aperture zoom lens, it is difficult to maintain optical performance over the entire zoom range, including that the Petzval sum is biased too negatively to make correction of field curvature difficult. .

  In order to eliminate the above-mentioned problems caused by the prior art, the present invention has a simple configuration, a zoom capable of high magnification with a wide angle of view while maintaining excellent optical performance and downsizing the optical system. The object is to provide a lens.

In order to solve the above-described problems and achieve the object, a zoom lens according to a first aspect of the present invention has a first lens group having a positive refractive power and a negative refractive power, which are arranged in order from the object side. A second lens group; a third lens group having a positive refractive power; a fourth lens group having a negative refractive power; and a fifth lens group having a positive refractive power; and the first lens group. Includes a cemented lens composed of a negative lens and a positive lens, and two lenses having a positive refractive power, and the Abbe number in the d-line of the negative lens constituting the cemented lens is represented by ν _ln . When the Abbe number at the d-line of the positive lens is ν _lp , the following conditional expression is satisfied.
(1) 35 <ν _lp −ν _ln <44

  According to the first aspect of the present invention, various aberrations can be effectively corrected over the entire zooming range.

According to a second aspect of the present invention, in the zoom lens according to the first aspect, the focal length of the first lens group is f ₁ and the focal length at the telephoto end of the entire zoom lens system is f _t . The following conditional expression is satisfied.
_{(2) 0.27 <f 1 /} f t <0.33

  According to the second aspect of the invention, the overall length of the optical system can be shortened, and the refractive power of the first lens group can be optimized to correct various aberrations.

A zoom lens according to a third aspect of the present invention is the zoom lens according to the first or second aspect, wherein the focal length of the third lens group is f ₃ and the focal length at the wide angle end of the entire zoom lens system is f _w The following conditional expression is satisfied.
(3) 3.5 <f ₃ / f _w <4.0

  According to the third aspect of the present invention, the overall length of the optical system can be shortened, and the refractive power of the third lens group can be optimized to satisfactorily correct various aberrations.

A zoom lens according to a fourth aspect of the present invention is the zoom lens according to any one of the first to third aspects, wherein the focal length of the fourth lens group is f ₄ and the focal length of the fifth lens group is the same. When f ₅ , the following conditional expression is satisfied.
(4) 0.7 <| f ₄ / f ₅ | <1.0

  According to the fourth aspect of the present invention, it is possible to satisfactorily correct various aberrations caused by the variation in the focus distance.

  According to the present invention, it is possible to provide a zoom lens capable of maintaining a high optical performance capable of effectively correcting various aberrations over the entire zoom range, and having a small size, a wide angle, and a high zoom ratio. There is an effect.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 1; FIG. 6 is a diagram illustrating various aberrations at an intermediate end of the zoom lens according to the first example. FIG. 7 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 1; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 2; FIG. 10 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 2; FIG. 6 is a diagram illustrating various aberrations at an intermediate end of the zoom lens according to the second example. FIG. 10 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 2; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to Example 3; FIG. 10 is a diagram illustrating all aberrations at the wide-angle end of the zoom lens according to Example 3; FIG. 9 is a diagram illustrating various aberrations at an intermediate end of the zoom lens according to the third example. FIG. 10 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to Example 3;

  Preferred embodiments of a zoom lens according to the present invention will be described below in detail with reference to the accompanying drawings.

  The zoom lens according to this embodiment includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side. It includes a lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power.

  The zoom lens according to this embodiment performs zooming from the wide angle end to the telephoto end by moving the second lens group from the object side to the image plane side along the optical axis. Further, the fourth lens group is moved along the optical axis to correct or focus on image plane fluctuation (image forming position) accompanying zooming. The first lens group, the third lens group, and the fifth lens group are always fixed.

  An object of the present invention is to provide a zoom lens that maintains high optical performance over the entire zoom range, is small, has a wide angle, and is capable of high zooming of about 55 times. Therefore, in order to achieve this purpose, various conditions as shown below are set.

The first lens group includes a cemented lens composed of a negative lens and a positive lens, and two positive lenses in order from the object side. When the Abbe number of the negative lens constituting the cemented lens is ν _ln and the Abbe number of the positive lens constituting the cemented lens is ν _lp , the following conditional expression is satisfied. preferable.
(1) 35 <ν _lp −ν _ln <44

  Conditional expression (1) is an expression that defines a difference in Abbe number between the negative lens and the positive lens constituting the cemented lens in the first lens group at the d-line. If the upper limit of conditional expression (1) is exceeded, it will be difficult to correct axial chromatic aberration of the g-line at the telephoto end of the zoom lens. On the other hand, if the lower limit of conditional expression (1) is not reached, the refractive power of each lens must be increased in order to correct axial chromatic aberration, and as a result, correction of various aberrations including spherical aberration becomes difficult. Inconvenience occurs.

The zoom lens of this embodiment, the focal length f ₁ of the first lens group, the focal length at the telephoto end of the zoom lens system and f _t, to satisfy the following condition: preferable.
_{(2) 0.27 <f 1 /} f t <0.33

  Conditional expression (2) is an expression that defines the ratio between the focal length of the first lens group and the focal length at the telephoto end of the entire zoom lens system, and achieves shortening of the total length of the optical system. This shows the conditions for realizing good correction of various aberrations by optimizing the refractive power of one lens unit. If the lower limit of conditional expression (2) is not reached, the refractive power of the first lens group becomes too strong, and it becomes difficult to correct various aberrations including spherical aberration at the telephoto end of the zoom lens. On the other hand, if the upper limit in conditional expression (2) is exceeded, the refractive power of the first lens group becomes too weak and the total length of the optical system increases.

  The second lens group includes, in order from the object side, a negative lens and a cemented lens including a negative lens and a positive lens. Alternatively, a negative lens, a cemented lens including a negative lens and a positive lens, and a negative lens are arranged in this order from the object side. Here, chromatic aberration can be favorably corrected by disposing a cemented lens in the second lens group.

  The third lens group includes, in order from the object side, a positive lens, a cemented lens including a negative lens and a positive lens, and a positive lens. An aspherical surface is formed on at least one of the positive lenses constituting the third lens group. In this way, various aberrations including spherical aberration can be corrected satisfactorily.

The third lens group having a focal length of f _3, when the focal length at the wide-angle end of the zoom lens system and f _w, it is preferable to satisfy the following condition.
(3) 3.5 <f ₃ / f _w <4.0

  Conditional expression (3) defines the ratio between the focal length of the third lens group and the focal length at the wide-angle end of the entire zoom lens system, and achieves a reduction in the overall length of the optical system. This shows the conditions for achieving good correction of various aberrations by optimizing the refractive powers of the three lens groups. If the lower limit of conditional expression (3) is not reached, the refractive power of the third lens group becomes too strong, making it difficult to correct various aberrations including spherical aberration at the wide angle end of the zoom lens. On the other hand, if the upper limit in conditional expression (3) is exceeded, the refractive power of the third lens group becomes too weak, and the rear lens group (after the third lens group) cannot be reduced, and the fourth lens group. It is difficult to ensure the amount of movement necessary for image plane correction and focusing.

  The fourth lens group includes a positive lens and a negative lens arranged in this order from the object side. An aspherical surface is formed on at least one surface of the negative lens constituting the fourth lens group. By providing an aspherical surface in the fourth lens group, it is possible to correct various aberrations with a small number of lenses. In addition, a sufficient amount of movement of the fourth lens group can be ensured, and correction of image plane variation (imaging position) accompanying zooming and focusing can be performed effectively.

  The fifth lens group includes a negative lens and a positive lens arranged in this order from the object side.

When the focal length of the fourth lens group is f ₄ and the focal length of the fifth lens group is f ₅ , it is preferable that the following conditional expression is satisfied.
(4) 0.7 <| f ₄ / f ₅ | <1.0

  Conditional expression (4) defines the ratio between the focal length of the fourth lens group and the focal length of the fifth lens group. If the lower limit of conditional expression (4) is not reached, the refractive power of the fourth lens group becomes too strong, making it difficult to correct various aberrations including spherical aberration due to fluctuations in focus distance. On the other hand, if the upper limit of conditional expression (4) is exceeded, the refractive power of the fourth lens group becomes too weak, and it is difficult to ensure the amount of movement necessary for image plane correction and focusing by the fourth lens group. become. In addition, when the refractive power of the fifth lens group becomes too strong compared to the fourth lens group, the back focus becomes too short, and there is a disadvantage that it is difficult to secure a space for inserting a filter or a cover glass.

  As described above, since the zoom lens according to this embodiment has the above-described features, it is possible to effectively reduce various aberrations over the entire zooming range without impairing the compactness of the optical system. High magnification can be achieved while maintaining high optical performance that can be corrected. In particular, the zoom lens according to this embodiment satisfies the above-described conditional expressions, so that it is possible to overcome the difficulty of aberration correction that has been a problem with wide-angle and high-magnification zoom lenses.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the first embodiment. The zoom lens includes a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and a third lens group G ₁₃ having a positive refractive power in order from an object side (not shown). The fourth lens group G ₁₄ having a negative refractive power and the fifth lens group G ₁₅ having a positive refractive power are arranged. Further, the second lens group G ₁₂ between the third lens group G _13, stop STP is disposed. Between the fifth lens group G ₁₅ and the image plane IMG, in order from the object side, the filter FT made of an infrared cut filter or a low pass filter, a cover glass CG is disposed. The filter FT and the cover glass CG are arranged as necessary, and can be omitted if unnecessary. In addition, a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₁₁ is constituted from the object side, a negative lens L _111, a positive lens L _112, a positive lens L _113, and the positive lens L ₁₁₄ are arranged. The negative lens L ₁₁₁ and the positive lens L ₁₁₂ are cemented.

The second lens group G ₁₂ includes a negative lens L ₁₂₁ , a negative lens L ₁₂₂ , and a positive lens L ₁₂₃ arranged in this order from the object side. The negative lens L ₁₂₂ and the positive lens L ₁₂₃ are cemented.

The third lens group G ₁₃ includes a positive lens L ₁₃₁ , a negative lens L ₁₃₂ , a positive lens L ₁₃₃ , and a positive lens L ₁₃₄ arranged in order from the object side. The negative lens L ₁₃₂ and the positive lens L ₁₃₃ are cemented. Further, aspheric surfaces are formed on the object side surfaces of the positive lens L ₁₃₁ and the positive lens L ₁₃₄ , respectively.

The fourth lens group G ₁₄ includes, in order from the object side, a positive lens L _141, configured negative lens L ₁₄₂ are arranged. The positive lens L ₁₄₁ and the negative lens L ₁₄₂ are cemented. Further, an aspheric surface is formed on the side surface of the image plane IMG of the negative lens L ₁₄₂ .

The fifth lens group G ₁₅ includes a negative lens L ₁₅₁ and a positive lens L ₁₅₂ arranged in order from the object side. The negative lens L ₁₅₁ and the positive lens L ₁₅₂ are cemented.

The zoom lens, by moving from the object side along the second lens group G ₁₂ in the optical axis toward the image plane IMG side performs zooming from the wide-angle end to the telephoto end. Further, by moving along the fourth lens group G ₁₄ to the optical axis is corrected and focusing of image plane variation due to magnification (imaging position). The first lens group G ₁₁ , the third lens group G ₁₃ , and the fifth lens group G ₁₅ are always fixed.

  Various numerical data related to the zoom lens according to Example 1 will be described below.

Focal length (f _w ) = 6.00 mm at the wide-angle end of the entire zoom lens system
Focal length at the middle end of the entire zoom lens system = 45.1 mm
Focal length at the telephoto end of the zoom lens system (f _t) = 330mm
F number = 1.82 (wide-angle end) to 2.23 (intermediate end) to 6.12 (telephoto end)
Angle of view (2ω) = 62.2 ° (wide-angle end) to 8.1 ° (intermediate end) to 1.1 ° (telephoto end)

(Numerical values related to conditional expression (1))
Abbe number (ν _ln ) at the d-line of the negative lens L ₁₁₁ = 42.71
Abbe number (ν _lp ) = 81.54 in the d-line of the positive lens L ₁₁₂
ν _lp −ν _ln = 38.83

(Numerical value related to conditional expression (2))
Focal length (f ₁ ) = 107.82 of the first lens group G ₁₁
f ₁ / f _t = 0.327

(Numerical values related to conditional expression (3))
Focal length (f ₃ ) of the third lens group G ₁₃ = 23.28
f ₃ / f _w = 3.880

(Numerical values related to conditional expression (4))
Focal length (f ₄ ) of fourth lens group G ₁₄ = −19.25
Focal length (f ₅ ) of the fifth lens group G ₁₅ = 23.26
| F ₄ / f ₅ | = 0.828

r ₁ = 628.629
d ₁ = 2.500 nd ₁ = 1.83481 νd ₁ = 42.71
r ₂ = 80.402
d ₂ = 8.688 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = −365.347
d ₃ = 0.200
r ₄ = 87.972
d ₄ = 6.267 nd ₃ = 1.49700 νd ₃ = 81.54
r ₅ = 2937.246
d ₅ = 0.200
r ₆ = 79.204
d ₆ = 5.610 nd ₄ = 1.49700 νd ₄ = 81.54
r ₇ = 449.643
d ₇ = 1.970 (wide angle end) to 63.659 (intermediate end) to 87.798 (telephoto end)
r ₈ = −339.143
d ₈ = 1.500 nd ₅ = 1.88300 νd ₅ = 40.76
r ₉ = 18.066
d ₉ = 4.200
r ₁₀ = −22.191
d ₁₀ = 1.200 nd ₆ = 1.77250 νd ₆ = 49.60
r ₁₁ = 18.958
d ₁₁ = 3.247 nd ₇ = 1.92286 νd ₇ = 20.88
r ₁₂ = 1250.168
d ₁₂ = 87.854 (wide-angle end) to 26.166 (intermediate end) to 2.027 (telephoto end)
r ₁₃ = ∞ (aperture)
d ₁₃ = 1.800
r ₁₄ = 21.761 (aspherical surface)
d ₁₄ = 0.200 nd ₈ = 1.53610 νd ₈ = 41.21
r ₁₅ = 23.133
d ₁₅ = 5.580 nd ₉ = 1.61800 νd ₉ = 63.39
r ₁₆ = 145.555
d ₁₆ = 4.971
r ₁₇ = 58.051
d ₁₇ = 1.500 nd ₁₀ = 1.92286 νd ₁₀ = 20.88
r ₁₈ = 25.973
d ₁₈ = 4.727 nd ₁₁ = 1.49700 νd ₁₁ = 81.54
r ₁₉ = −113.813
d ₁₉ = 0.200
r ₂₀ = 26.258 (aspherical surface)
d ₂₀ = 0.200 nd ₁₂ = 1.53610 νd ₁₂ = 41.21
r ₂₁ = 31.514
d ₂₁ = 3.355 nd ₁₃ = 1.61800 νd ₁₃ = 63.39
r ₂₂ = −1442.190
d ₂₂ = 2.848 (wide-angle end) to 13.961 (intermediate end) to 2.900 (telephoto end)
r ₂₃ = −2250.446
d ₂₃ = 4.0000 nd ₁₄ = 1.84666 νd ₁₄ = 23.78
r ₂₄ = −25.866
d ₂₄ = 1.200 nd ₁₅ = 1.77250 νd ₁₅ = 49.60
r ₂₅ = 14.035
d ₂₅ = 0.200 nd ₁₆ = 1.53610 νd ₁₆ = 41.21
r ₂₆ = 14.267 (aspherical surface)
d ₂₆ = 21.119 (wide-angle end) to 10.006 (intermediate end) to 21.067 (telephoto end)
r ₂₇ = 12.056
d ₂₇ = 1.200 nd ₁₇ = 1.84666 νd ₁₇ = 23.78
r ₂₈ = 8.142
d ₂₈ = 3.879 nd ₁₈ = 1.61800 νd ₁₈ = 63.39
r ₂₉ = 1255.591
d ₂₉ = 1.000
r ₃₀ = ∞
d ₃₀ = 0.500 nd ₁₉ = 1.51633 νd ₁₉ = 64.14
r ₃₁ = ∞
d ₃₁ = 4.500
r ₃₂ = ∞
d ₃₂ = 3.500 nd ₂₀ = 1.51633 νd ₂₀ = 64.14
r ₃₃ = ∞
d ₃₃ = 0.107
r ₃₄ = ∞ (image plane)

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(14th page)
ε = 1.0000,
A = 0
B = −5.223637 × 10 ⁻⁶ , C = −1.71971 × 10 ⁻⁸ ,
D = 1.07328 × 10 ⁻¹¹ , E = −4.888864 × 10 ⁻¹⁴
(20th page)
ε = 1.0000,
A = 0
B = -2.47065 × 10 ⁻⁵ , C = −7.771176 × 10 ⁻⁸ ,
D = 4.088847 × 10 ⁻¹⁰ , E = −2.61922 × 10 ⁻¹²
(26th page)
ε = 1.0000,
A = 0
B = -1.35793 × 10 ⁻⁵ , C = −5.61543 × 10 ⁻⁸ ,
D = −8.2418 × 10 ⁻⁹ , E = 1.56660 × 10 ⁻¹⁰

  FIG. 2 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the first example. FIG. 3 is a diagram illustrating various aberrations at the intermediate end of the zoom lens according to the first example. FIG. 4 is a diagram illustrating various aberrations at the telephoto end of the zoom lens according to the first example. In the figure, FNo represents the F number, and 2ω represents the angle of view. G represents g-line (λ = 435.83 nm), d represents d-line (λ = 587.56 nm), and c represents aberration of a wavelength corresponding to c-line (λ = 656.27 nm). Symbols ΔS and ΔM in the astigmatism diagrams represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the second embodiment. The zoom lens includes a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a negative refractive power, and a third lens group G ₂₃ having a positive refractive power in order from an object side (not shown). The fourth lens group G ₂₄ having a negative refractive power and the fifth lens group G ₂₅ having a positive refractive power are arranged. A stop STP is disposed between the second lens group G ₂₂ and the third lens group G ₂₃ . Between the fifth lens group G ₂₅ and the image plane IMG, a filter FT composed of an infrared cut filter, a low-pass filter, and the like, and a cover glass CG are arranged in this order from the object side. The filter FT and the cover glass CG are arranged as necessary, and can be omitted if unnecessary. In addition, a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₂₁ includes a negative lens L ₂₁₁ , a positive lens L ₂₁₂ , a positive lens L ₂₁₃ , and a positive lens L ₂₁₄ arranged in order from the object side. The negative lens L ₂₁₁ and the positive lens L ₂₁₂ are cemented.

The second lens group G ₂₂ includes, formed from said object side, a negative lens L _221, a negative lens L _222, a positive lens L _223, and a negative lens L ₂₂₄ are arranged. The negative lens L ₂₂₂ and the positive lens L _223, and is joined.

The third lens group G ₂₃ is constituted from the object side, a positive lens L _231, a negative lens L _232, a positive lens L _233, and the positive lens L ₂₃₄ is disposed. The negative lens L ₂₃₂ and the positive lens L ₂₃₃ are cemented. In addition, aspheric surfaces are formed on the object side surfaces of the positive lens L ₂₃₁ and the positive lens L ₂₃₄ , respectively.

The fourth lens group G ₂₄ includes a positive lens L ₂₄₁ and a negative lens L ₂₄₂ arranged in this order from the object side. The positive lens L ₂₄₁ and the negative lens L ₂₄₂ are cemented. On the image plane IMG side of the negative lens L _242, aspheric surface is formed.

The fifth lens group G ₂₅ includes a negative lens L ₂₅₁ and a positive lens L ₂₅₂ arranged in order from the object side. The negative lens L ₂₅₁ and the positive lens L ₂₅₂ are cemented.

The zoom lens, by moving from the object side along the second lens group G ₂₂ in the optical axis toward the image plane IMG side performs zooming from the wide-angle end to the telephoto end. Further, by moving along the fourth lens group G ₂₄ to the optical axis is corrected and focusing of image plane variation accompanying the magnification (imaging position). The first lens group G ₂₁ , the third lens group G ₂₃ , and the fifth lens group G ₂₅ are always fixed.

  Various numerical data related to the zoom lens according to Example 2 will be described below.

Focal length (f _w ) = 6.00 mm at the wide-angle end of the entire zoom lens system
Focal length at the middle end of the entire zoom lens = 44.1 mm
Focal length at the telephoto end of the zoom lens system (f _t) = 330mm
F number = 1.82 (wide angle end) to 2.25 (intermediate end) to 6.10 (telephoto end)
Angle of view (2ω) = 60.0 ° (wide-angle end) to 8.3 ° (intermediate end) to 1.1 ° (telephoto end)

(Numerical values related to conditional expression (1))
Abbe number (ν _ln ) at the d-line of the negative lens L ₂₁₁ = 42.71
Abbe number (ν _lp ) = 81.54 in the d-line of the positive lens L ₂₁₂
ν _lp −ν _ln = 38.83

(Numerical value related to conditional expression (2))
Focal length (f ₁ ) of the first lens group G ₂₁ = 95.50
f ₁ / f _t = 0.289

(Numerical values related to conditional expression (3))
Focal length (f ₃ ) of the third lens group G ₂₃ = 22.50
f ₃ / f _w = 3.750

(Numerical values related to conditional expression (4))
Focal length (f ₄ ) of fourth lens group G ₂₄ = -15.72
Focal length (f ₅ ) = 20.94 of the fifth lens group G ₂₅
| F ₄ / f ₅ | = 0.750

r ₁ = 873.775
d ₁ = 2.500 nd ₁ = 1.83481 νd ₁ = 42.71
r ₂ = 73.535
d ₂ = 12.200 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = −257.818
d ₃ = 0.200
r ₄ = 81.531
d ₄ = 8.0000 nd ₃ = 1.49700 νd ₃ = 81.54
r ₅ = 6696.081
d ₅ = 0.200
r ₆ = 71.004
d ₆ = 6.800 nd ₄ = 1.49700 νd ₄ = 81.54
r ₇ = 431.378
d ₇ = 1.987 (wide angle end) to 55.951 (intermediate end) to 76.261 (telephoto end)
r ₈ = 157.153
d ₈ = 1.500 nd ₅ = 1.88300 νd ₅ = 40.76
r ₉ = 14.203
d ₉ = 4.0000
r ₁₀ = −50.906
d ₁₀ = 1.200 nd ₆ = 1.77250 νd ₆ = 49.60
r ₁₁ = 13.178
d ₁₁ = 3.800 nd ₇ = 1.92286 νd ₇ = 20.88
r ₁₂ = 99.974
d ₁₂ = 2.500
r ₁₃ = −16.428
d ₁₃ = 1.200 nd ₈ = 1.80610 νd ₈ = 33.27
r ₁₄ = −25.765
d ₁₄ = 76.316 (wide-angle end) to 22.351 (intermediate end) to 2.042 (telephoto end)
r ₁₅ = ∞ (aperture)
d ₁₅ = 1.300
r ₁₆ = 24.505 (aspherical surface)
d ₁₆ = 0.200 nd ₉ = 1.53610 νd ₉ = 41.21
r ₁₇ = 26.591
d ₁₇ = 7.200 nd ₁₀ = 1.61800 νd ₁₀ = 63.39
r ₁₈ = −1147.714
d ₁₈ = 4.726
r ₁₉ = 53.199
d ₁₉ = 1.500 nd ₁₁ = 1.92286 νd ₁₁ = 20.88
r ₂₀ = 25.167
d ₂₀ = 6.00 nd ₁₂ = 1.49700 νd ₁₂ = 81.54
r ₂₁ = −349.403
d ₂₁ = 0.200
r ₂₂ = 2.951 (aspherical surface)
d ₂₂ = 0.200 nd ₁₃ = 1.53610 νd ₁₃ = 41.21
r ₂₃ = 24.974
d ₂₃ = 5.000 nd ₁₄ = 1.48749 νd ₁₄ = 70.24
r ₂₄ = −60.537
d ₂₄ = 2.899 (wide-angle end) ～12.912 (middle end) ～2.861 (telephoto end)
r ₂₅ = −753.567
d ₂₅ = 3.000 nd ₁₅ = 1.84666 νd ₁₅ = 23.78
r ₂₆ = −22.060
d ₂₆ = 1.200 nd ₁₆ = 1.77250 νd ₁₆ = 49.60
r ₂₇ = 11.766
d ₂₇ = 0.200 nd ₁₇ = 1.53610 νd ₁₇ = 41.21
r ₂₈ = 11.741 (aspherical surface)
d ₂₈ = 19.259 (wide-angle end) to 9.245 (intermediate end) to 19.296 (telephoto end)
r ₂₉ = 1.907
d ₂₉ = 1.200 nd ₁₈ = 1.84666 νd ₁₈ = 23.78
r ₃₀ = 8.010
d ₃₀ = 4.0000 nd ₁₉ = 1.61800 νd ₁₉ = 63.39
r ₃₁ = −134.663
d ₃₁ = 1.000
r ₃₂ = ∞
d ₃₂ = 0.500 nd ₂₀ = 1.51633 νd ₂₀ = 64.14
r ₃₃ = ∞
d ₃₃ = 5.200
r ₃₄ = ∞
d ₃₄ = 2.500 nd ₂₁ = 1.51633 νd ₂₁ = 64.14
r ₃₅ = ∞
d ₃₅ = 0.110
r ₃₆ = ∞ (image plane)

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(16th surface)
ε = 1.0000,
A = 0
B = −6.335402 × 10 ⁻⁶ , C = −2.424383 × 10 ⁻⁸ ,
D = 3.62247 × 10 ⁻¹¹ , E = −8.777579 × 10 ⁻¹⁴
(Twenty-second surface)
ε = 1.0000,
A = 0
B = -2.75341 × 10 ⁻⁵ , C = −3.118129 × 10 ⁻⁸ ,
D = 8.55421 × 10 ⁻¹¹ , E = −5.666320 × 10 ⁻¹³
(Section 28)
ε = 1.0000,
A = 0
B = −2.18710 × 10 ⁻⁵ , C = −9.28709 × 10 ⁻⁷ ,
D = 1.71800 × 10 ⁻⁸ , E = −1.23004 × 10 ⁻¹⁰

  FIG. 6 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the second example. FIG. 7 is a diagram of various aberrations at the intermediate end of the zoom lens according to the second example. FIG. 8 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to the second example. In the figure, FNo represents the F number, and 2ω represents the angle of view. G represents g-line (λ = 435.83 nm), d represents d-line (λ = 587.56 nm), and c represents aberration of a wavelength corresponding to c-line (λ = 656.27 nm). Symbols ΔS and ΔM in the astigmatism diagrams represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

FIG. 9 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the third example. The zoom lens includes a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and a third lens group G ₃₃ having a positive refractive power in order from an object side (not shown). The fourth lens group G ₃₄ having negative refractive power and the fifth lens group G ₃₅ having positive refractive power are arranged. A stop STP is disposed between the second lens group G ₃₂ and the third lens group G ₃₃ . Between the fifth lens group G ₃₅ and the image plane IMG, a filter FT composed of an infrared cut filter, a low-pass filter, and the like, and a cover glass CG are arranged in this order from the object side. The filter FT and the cover glass CG are arranged as necessary, and can be omitted if unnecessary. In addition, a light receiving surface of an image sensor such as a CCD or a CMOS is disposed on the image plane IMG.

The first lens group G ₃₁ includes a negative lens L ₃₁₁ , a positive lens L ₃₁₂ , a positive lens L ₃₁₃ , and a positive lens L ₃₁₄ arranged in order from the object side. The negative lens L ₃₁₁ and the positive lens L ₃₁₂ are cemented.

The second lens group G ₃₂ is constituted from the object side, a negative lens L _321, a negative lens L _322, a positive lens L _323, and a negative lens L ₃₂₄ are arranged. The negative lens L ₃₂₂ and the positive lens L ₃₂₃ are cemented.

The third lens group G ₃₃ includes a positive lens L ₃₃₁ , a negative lens L ₃₃₂ , a positive lens L ₃₃₃ , and a positive lens L ₃₃₄ arranged in order from the object side. The negative lens L ₃₃₂ and the positive lens L ₃₃₃ are cemented. Further, aspheric surfaces are formed on the object side surfaces of the positive lens L ₃₃₁ and the positive lens L ₃₃₄ , respectively.

The fourth lens group G ₃₄ includes a positive lens L ₃₄₁ and a negative lens L ₃₄₂ arranged in order from the object side. The positive lens L ₃₄₁ and the negative lens L ₃₄₂ are cemented. On the image plane IMG side of the negative lens L _342, aspheric surface is formed.

The fifth lens group G ₃₅ includes a negative lens L ₃₅₁ and a positive lens L ₃₅₂ arranged in this order from the object side. The negative lens L ₃₅₁ and the positive lens L ₃₅₂ are cemented.

The zoom lens, by moving from the object side along the second lens group G ₃₂ in the optical axis toward the image plane IMG side performs zooming from the wide-angle end to the telephoto end. Further, by moving along the fourth lens group G ₃₄ to the optical axis we are corrected and focusing of image plane variation due to magnification (imaging position). The first lens group G ₃₁ , the third lens group G ₃₃ , and the fifth lens group G ₃₅ are always fixed.

  Various numerical data relating to the zoom lens according to Example 3 will be described below.

Focal length (f _w ) = 6.00 mm at the wide-angle end of the entire zoom lens system
Focal length at the middle end of the entire zoom lens system = 44.4 mm
Focal length at the telephoto end of the zoom lens system (f _t) = 330mm
F number = 1.82 (wide angle end) to 2.24 (intermediate end) to 6.12 (telephoto end)
Angle of view (2ω) = 61.1 ° (wide-angle end) to 8.3 ° (intermediate end) to 1.1 ° (telephoto end)

(Numerical values related to conditional expression (1))
Abbe number (ν _ln ) of the negative lens L _{311 at} the d-line = 42.71
Abbe number (ν _lp ) = 81.54 in the d-line of the positive lens L ₃₁₂
ν _lp −ν _ln = 38.83

(Numerical value related to conditional expression (2))
Focal length (f ₁ ) of the first lens group G ₃₁ = 95.28
f ₁ / f _t = 0.289

(Numerical values related to conditional expression (3))
Focal length (f ₃ ) of the third lens group G ₃₃ = 22.37
f ₃ / f _w = 3.729

(Numerical values related to conditional expression (4))
Focal length (f ₄ ) of fourth lens group G ₃₄ = −16.09
Focal length (f ₅ ) of the fifth lens group G ₃₅ = 21.36
| F ₄ / f ₅ | = 0.553

r ₁ = 79.673
d ₁ = 2.500 nd ₁ = 1.83481 νd ₁ = 42.71
r ₂ = 73.778
d ₂ = 10.174 nd ₂ = 1.49700 νd ₂ = 81.54
r ₃ = −263.780
d ₃ = 0.200
r ₄ = 80.175
d ₄ = 7.181 nd ₃ = 1.49700 νd ₃ = 81.54
r ₅ = 4029.349
d ₅ = 0.200
r ₆ = 70.278
d ₆ = 6.308 nd ₄ = 1.49700 νd ₄ = 81.54
r ₇ = 396.810
d ₇ = 1.962 (wide-angle end) to 55.974 (intermediate end) to 76.302 (telephoto end)
r ₈ = −598.754
d ₈ = 1.500 nd ₅ = 1.88300 νd ₅ = 40.76
r ₉ = 15.686
d ₉ = 4.0000
r ₁₀ = −43.914
d ₁₀ = 1.200 nd ₆ = 1.77250 νd ₆ = 49.60
r ₁₁ = 14.136
d ₁₁ = 3.500 nd ₇ = 1.92286 νd ₇ = 20.88
r ₁₂ = 116.272
d ₁₂ = 2.035
r ₁₃ = −21.060
d ₁₃ = 1.200 nd ₈ = 1.83400 νd ₈ = 37.16
r ₁₄ = −33.746
d ₁₄ = 76.372 (wide-angle end) to 22.360 (intermediate end) to 2.033 (telephoto end)
r ₁₅ = ∞ (aperture)
d ₁₅ = 1.300
r ₁₆ = 23.367 (aspherical surface)
d ₁₆ = 0.200 nd ₉ = 1.53610 νd ₉ = 41.21
r ₁₇ = 25.239
d ₁₇ = 5.971 nd ₁₀ = 1.61800 νd ₁₀ = 63.39
r ₁₈ = 34290.588
d ₁₈ = 6.144
r ₁₉ = 83.169
d ₁₉ = 1.500 nd ₁₁ = 1.92286 νd ₁₁ = 20.88
r ₂₀ = 30.105
d ₂₀ = 4.527 nd ₁₂ = 1.49700 νd ₁₂ = 81.54
r ₂₁ = −104.257
d ₂₁ = 0.200
r ₂₂ = 21.542 (aspherical surface)
d ₂₂ = 0.200 nd ₁₃ = 1.53610 νd ₁₃ = 41.21
r ₂₃ = 24.092
d ₂₃ = 4.787 nd ₁₄ = 1.48749 νd ₁₄ = 70.24
r ₂₄ = −84.407
d ₂₄ = 2.809 (wide-angle end) to 12.915 (intermediate end) to 2.856 (telephoto end)
r ₂₅ = −1485.826
d ₂₅ = 2.957 nd ₁₅ = 1.84666 νd ₁₅ = 23.78
r ₂₆ = −24.241
d ₂₆ = 1.200 nd ₁₆ = 1.77250 νd ₁₆ = 49.60
r ₂₇ = 12.870
d ₂₇ = 0.200 nd ₁₇ = 1.53610 νd ₁₇ = 41.21
r ₂₈ = 11.594 (aspherical surface)
d ₂₈ = 20.044 (wide-angle end) to 9.939 (intermediate end) to 19.998 (telephoto end)
r ₂₉ = 11.743
d ₂₉ = 1.200 nd ₁₈ = 1.84666 νd ₁₈ = 23.78
r ₃₀ = 8.088
d ₃₀ = 4.0000 nd ₁₉ = 1.61800 νd ₁₉ = 63.39
r ₃₁ = −311.620
d ₃₁ = 1.000
r ₃₂ = ∞
d ₃₂ = 0.500 nd ₂₀ = 1.51633 νd ₂₀ = 64.14
r ₃₃ = ∞
d ₃₃ = 4.500
r ₃₄ = ∞
d ₃₄ = 3.500 nd ₂₁ = 1.51633 νd ₂₁ = 64.14
r ₃₅ = ∞
d ₃₅ = 0.050
r ₃₆ = ∞ (image plane)

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(16th surface)
ε = 1.0000,
A = 0
B = −6.62093 × 10 ⁻⁶ , C = −1.87750 × 10 ⁻⁸ ,
D = 3.39027 × 10 ⁻¹² , E = −1.87213 × 10 ⁻¹⁴
(Twenty-second surface)
ε = 1.0000,
A = 0
B = −2.669258 × 10 ⁻⁵ , C = −9.28801 × 10 ⁻⁸ ,
D = 6.67082 × 10 ⁻¹⁰ , E = −3.335828 × 10 ⁻¹²
(Section 28)
ε = 1.0000,
A = 0
B = −2.43565 × 10 ⁻⁵ , C = −6.77926 × 10 ⁻⁷ ,
D = 1.55754 × 10 ⁻⁹ , E = 1.290309 × 10 ⁻¹⁰

  FIG. 10 is a diagram illustrating various aberrations at the wide-angle end of the zoom lens according to the third example. FIG. 11 is a diagram illustrating various aberrations at the intermediate end of the zoom lens according to the third example. FIG. 12 is a diagram illustrating all aberrations at the telephoto end of the zoom lens according to the third example. In the figure, FNo represents the F number, and 2ω represents the angle of view. G represents g-line (λ = 435.83 nm), d represents d-line (λ = 587.56 nm), and c represents aberration of a wavelength corresponding to c-line (λ = 656.27 nm). Symbols ΔS and ΔM in the astigmatism diagrams represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively.

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the respective lenses and diaphragm surfaces, and d ₁ , d ₂ ,. Thickness or distance between them, nd ₁ , nd ₂ ,... Is the refractive index at d-line (λ = 587.56 nm) of each lens, νd ₁ , νd ₂ ,. The Abbe number at d line (λ = 587.56 nm) is shown.

  Each of the aspherical shapes is expressed by the following expression when the optical axis direction is X, the height from the optical axis is H, and the light traveling direction is positive.

  Here, R is a paraxial radius of curvature, ε is a conical coefficient, and A, B, C, D, and E are second-order, fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.

  As described above, according to the zoom lenses of the above-described embodiments, by satisfying the above conditional expressions, it is possible to correct aberrations over the entire zoom range, and to reduce the size and zoom ratio ( About 55 times) and widening (about 60 °) can be achieved.

  In addition, since the zoom lens according to each of the embodiments includes a lens having an aspherical surface, various aberrations can be favorably corrected with a small number of lenses.

  As described above, the zoom lens of the present invention is useful for video cameras, surveillance cameras, and the like that require miniaturization, high zoom ratio, and wide angle, and is particularly suitable when high optical performance is required. It is.

G ₁₁ 1st lens group G ₁₂ 2nd lens group G ₁₃ 3rd lens group G ₁₄ 4th lens group G ₁₅ 5th lens group IMG Image surface STP Aperture FT Filter CG Cover glass

Claims (4)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a negative refractive power, which are arranged in order from the object side. A fourth lens group, and a fifth lens group having positive refractive power,
The first lens group includes a cemented lens including a negative lens and a positive lens, and two lenses having a positive refractive power,
When the Abbe number of the negative lens constituting the cemented lens is ν _ln and the Abbe number of the positive lens constituting the cemented lens is ν _lp , the following conditional expression is satisfied: Zoom lens to be used.
(1) 35 <ν _lp −ν _ln <44 2. The zoom lens according to claim ₁ , wherein the following conditional expression is satisfied, where f _{1 is} a focal length of the first lens unit and f _t is a focal length at the telephoto end of the entire zoom lens system. .
_{(2) 0.27 <f 1 /} f t <0.33 Focal length f ₃ of the third lens group, when the focal length at the wide angle end of the zoom lens system and f _w, according to claim 1 or 2, characterized by satisfying the following condition: Zoom lens.
(3) 3.5 <f ₃ / f _w <4.0 Wherein the focal length of the fourth lens group f _4, a focal length of the fifth lens group when the f _5, in any one of claims 1 to 3, characterized by satisfying the following condition: The described zoom lens.
(4) 0.7 <| f ₄ / f ₅ | <1.0

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