# Patent

## Title
Zoom lens

## Abstract

A zoom lens includes sequentially from an object side, a positive first lens group; a negative second lens group; a diaphragm; a positive third lens group; a positive fourth lens group; and a positive fifth lens group, wherein a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied. SLW is a distance from the diaphragm at a wide angle edge to an imaging plane; SLM is a distance from the diaphragm at an intermediate zoom position to the imaging plane; SLT is a distance from the diaphragm at a telephoto edge to the imaging plane; FW is optical system focal length for infinity at the wide angle edge; and F14t is a combined focal length for the first to the fourth lens groups at the telephoto edge.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-158657, filed on Jul. 3, 2009, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a large diameter, high power zoom lens.
2. Description of the Related Art
Conventionally, a large number of variable focus lenses aimed at achieving high zoom ratios have been proposed. Such variable focus lenses, for example, include sequentially from an object side at least a positive first lens group, a negative lens group, a positive third lens group, a positive fourth lens group, and a positive fifth lens group, and focuses an image of an object by moving the fifth lens group (refer to Japanese Patent Application Laid-Open Publication Nos. 2005-345714 and 2001-75008).
The zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2005-345714 includes at least 5 lens groups that are positive, negative, positive, positive, and positive respectively from the object side, has an angle of view exceeding 62° at the wide angle edge, and realizes a zoom ratio of 11.3 or greater. Further, the zoom lens recited in Japanese Patent Application Laid-Open Publication No. 2001-75008 includes at least 6 lens groups that are positive, negative, positive, positive, negative, and positive respectively from the object side, has an angle of view exceeding 42° at the wide angle edge, and realizes a zoom ratio of 11.1 or greater.
Although the zoom lenses recited respectively in Japanese Patent Application Laid-Open Publication Nos. 2005-345714 and 2001-75008 realize high zoom ratios of 11 or greater, the F number also significantly increases accompanying zoom and thus, enlarged images become dark. Furthermore, the angle of view is insufficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to at least solve the above problems in the conventional technologies.
A zoom lens according to one aspect of the present invention includes sequentially from an object side, a positive first lens group; a negative second lens group; a diaphragm; a positive third lens group; a positive fourth lens group; and a positive fifth lens group, wherein a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied. SLW is a distance from the diaphragm at a wide angle edge to an imaging plane; SLM is a distance from the diaphragm at an intermediate zoom position to the imaging plane; SLT is a distance from the diaphragm at a telephoto edge to the imaging plane; FW is optical system focal length for infinity at the wide angle edge; and F14t is a combined focal length for the first to the fourth lens groups at the telephoto edge.
The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view (along the optical axis) of a zoom lens according to a first example;
FIG. 2 is a diagram of various types of aberration of the zoom lens according to the first example;
FIG. 3 is a cross sectional view (along the optical axis) of a zoom lens according to a second example;
FIG. 4 is a diagram of various types of aberration of the zoom lens according to the second example;
FIG. 5 is a cross sectional view (along the optical axis) of a zoom lens according to a third example;
FIG. 6 is a diagram of various types of aberration of the zoom lens according to the third example;
FIG. 7 is a cross sectional view (along the optical axis) of a zoom lens according to a fourth example;
FIG. 8 is a diagram of various types of aberration of the zoom lens according to the fourth example;
FIG. 9 is a cross sectional view (along the optical axis) of a zoom lens according to a fifth example;
FIG. 10 is a diagram of various types of aberration of the zoom lens according to the fifth example;
FIG. 11 is a cross sectional view (along the optical axis) of a zoom lens according to a sixth example; and
FIG. 12 is a diagram of various types of aberration of the zoom lens according to the sixth example.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the accompanying drawings, exemplary embodiments according to the present invention are explained in detail below.
The zoom lens according to the embodiment includes sequentially from the object side, a positive first lens group, a negative second lens group, a diaphragm, a positive third lens group, a positive fourth lens group, and a positive fifth lens group. By moving any among the second to the fourth lens groups along the optical axis, the zoom lens zooms from the wide angle edge to the telephoto edge. By moving the fifth lens group along the optical axis, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image.
One object of the present invention is to provide a large diameter, high zoom ratio zoom lens that ensures a wide angle of view and is able to maintain a small F number over the entire zoom range. To achieve this object, various conditions are set as indicated below.
The zoom lens according to the embodiment preferably satisfies the following conditional expression, where a distance from the diaphragm at the wide angle edge to the imaging plane is SLW, a distance from the diaphragm at the intermediate zoom position to the imaging plane is SLM, and a distance from the diaphragm at the telephoto edge to the imaging plane is SLT, where the focal length of the entire optical system for infinity at the wide angle edge is FW.

0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0  (1)

Conditional expression (1) prescribes a condition to reduce the effective diameter of the first lens group while maintaining an angle of view of 70° or greater at the wide angle edge. By satisfying conditional expression (1), both wide angle and a reduction of the diameter of the first lens group are achievable. Below the lower limit of conditional expression (1), the effective diameter of the first lens group at the intermediate zoom position of the zoom lens becomes too large, making it difficult to achieve a reduction in the diameter of the first lens group while maintaining a wide angle of view. Above the upper limit of conditional expression (1), the effective diameter of the fifth lens group, which has a function of focusing, must be increased, resulting in an increased diameter of the fifth lens group and hence, the disadvantage of reduced focusing speed.
Further, the zoom lens according to the embodiment preferably satisfies the following conditional expression, where a combined focal length of the first to the fourth lens groups at the telephoto edge is F14.

F14t≦0  (2)

Conditional expression (2) prescribes a condition to reduce the effective diameters of the fourth and the fifth lens groups disposed behind the diaphragm, while maintaining a large diameter at the telephoto edge. By satisfying conditional expression (2), a bright image can be obtained even at the telephoto edge while at the same time, a reduction in the diameters of the fourth and the fifth lens groups can be achieved. Above the upper limit of conditional expression (2), reduction of the diameters of the fourth and the fifth lens groups becomes difficult and thus, values exceeding the upper limit are undesirable.
The zoom lens according to the embodiment preferably satisfies the following conditional expression, where among the lenses in the second lens group, the lens that is farthest on the object side has a surface on the object side that is formed to be aspheric, deviation of the paraxial curvature radius and the aspheric shape is S10 at a height that is 100% of the effective diameter of the aspheric surface, and the height of 100% of the effective diameter is H.

S10/H≧0.005  (3)

Conditional expression (3) prescribes the aspheric shape of the lens in the second lens group. In the second lens group, by forming the surface on the object side of the lens that is farthest on the object side to have an aspheric surface satisfying conditional expression (3), various types of aberration such as spherical aberration, astigmatism, distortion, etc. can be corrected well, over the entire zoom range. In the second lens group, if the surface on the object side of the lens that is farthest on the object side does not have an aspheric surface satisfying conditional expression (3), the correction of various types of aberration cannot be sufficiently performed.
As described above, by satisfying conditional expression (1) and (2), diameter reduction and maintenance of a wide angle of view are possible, making the zoom lens according to the present embodiment a large diameter zoom lens that is capable of high zoom ratios. Furthermore, in the second lens group, by forming the surface on the object side of the lens that is farthest on the object side to have an aspheric surface satisfying conditional expression (3), various types of aberration can be effectively corrected over the entire zoom range without sacrificing the compactness of the optical system.
FIG. 1 is a cross sectional view (along the optical axis) of a zoom lens according to a first example. The zoom lens includes, sequentially from a non-depicted object side, a positive first lens group G11, a negative second lens group G12, a positive third lens group G13, a positive fourth lens group G14; a positive fifth lens group G15, and a negative sixth G16. Further, a diaphragm STP is disposed between the second lens group G12 and the third lens group G13. A cover glass CG (or filter) is disposed between the sixth lens group G16 and an imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, an optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G11 includes, sequentially from the object side, a negative lens L111, a positive lens L112, a positive lens L113, and a positive lens L114. The negative lens L111 and the positive lens L112 are cemented together.
The second lens group G12 includes, sequentially from the object side, a negative lens L121, a negative lens L122, a positive lens L123, and a negative lens L124. The negative lens L122 and the positive lens L123 are cemented together. Further, a surface on the object side of the negative lens L121 is formed to be aspheric.
The third lens group G13 includes, sequentially from the object side, a positive lens L131 and a negative lens L132 that are cemented together.
The fourth lens group G14 includes, sequentially from the object side, a positive lens L141, a positive lens L142 and a negative lens L143. A surface on the object side of the positive lens L142 is aspheric. Further, the positive lens L142 and the negative lens L143 are cemented together.
The fifth lens group G15 includes, sequentially from the object side, a positive lens L151, a negative lens L152, and a positive lens L153. Both surfaces of the positive lens L151 are aspheric. Further, the negative lens L152 and the positive lens L153 are cemented together.
The sixth lens group G16 includes, sequentially from the object side, a negative lens L161 and a positive lens L162 that are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G12, the third lens group G13, and the fourth lens group G14 along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G15 along the optical axis. The first lens group G11 and the sixth lens group G16 remain fixed.
Various values related to the zoom lens according to the first example are indicated below.

    focal length of entire zoom lens=8.42 (wide angle edge) to 22.75 (intermediate zoom position) to 62.70 (telephoto edge)
    F number=2.85
    angle of view (2ω)=70.1° (wide angle edge) to 27.64° (intermediate zoom position) to 10.26° (telephoto edge)
    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=64.382
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=74.473
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=62.736
    focal length (FW) of entire optical system for infinity at wide angle edge=8.42
    (SLM−(SLW+SLT)/2)/FW=1.296
    (Values Related to Conditional Expression (2))
    F14t=−274.22
    (Values Related to Conditional Expression (3))
    deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G12=0.550
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G12=29.700
    S10/H=0.019
    r1=134.2328
    
        d1=1.6500 nd1=1.80610 υd1=33.27
    
    
    r2=60.3060
    
        d2=8.6001 nd2=1.49700 υd2=81.61
    
    
    r3=607.0146
    
        d3=0.1500
    
    
    r4=60.8304
    
        d4=6.2517 nd3=1.49700 υd3=81.61
    
    
    r5=281.3437
    
        d5=0.1500
    
    
    r6=63.3658
    
        d6=4.3249 nd4=1.61800 υd4=63.39
    
    
    r7=146.8250
    
        d7=0.9000 (wide angle edge) to 25.4067 (intermediate zoom position) to 45.0224 (telephoto edge)
    
    
    r8=309.6078 (aspheric surface)
    
        d8=0.3000 nd5=1.53610 υd5=41.00
    
    
    r9=149.0172
    
        d9=1.2000 nd6=1.88300 υd6=40.80
    
    
    r10=16.0674
    
        d10=7.6090
    
    
    r11=−26.6578
    
        d11=1.0000 nd7=1.49700 υd7=81.61
    
    
    r12=26.6578
    
        d12=5.4742 nd8=1.90366 υd8=31.31
    
    
    r13=−35.0742
    
        d13=1.2590
    
    
    r14=−22.9708
    
        d14=0.8000 nd9=1.48749 υd9=70.44
    
    
    r15=37.6804
    
        d15=45.9494 (wide angle edge) to 11.3508 (intermediate zoom position) to 3.4718 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.2000
    
    
    r17=44.1399
    
        d17=3.0954 nd10=1.61800 υd10=63.39
    
    
    r18=−16.0964
    
        d18=0.8000 nd11=1.56732 υd11=42.84
    
    
    r19=81.5134
    
        d19=6.2937 (wide angle edge) to 16.3856 (intermediate zoom position) to 4.6489 (telephoto edge)
    
    
    r20=17.4600
    
        d20=2.5000 nd12=1.84666 υd12=23.78
    
    
    r21=57.9358
    
        d21=0.1500
    
    
    r22=27.8066 (aspheric surface)
    
        d22=2.4494 nd13=1.61800 υd13=63.39
    
    
    r23=−99.1785
    
        d23=0.8000 nd14=1.90366 υd14=31.31
    
    
    r24=15.9500
    
        d24=12.7128 (wide angle edge) to 6.7148 (intermediate zoom position) to 5.8692 (telephoto edge)
    
    
    r25=16.7429 (aspheric surface)
    
        d25=6.0463 nd15=1.61800 υd15=63.39
    
    
    r26=−31.9401 (aspheric surface)
    
        d26=0.1500
    
    
    r27=−86.2525
    
        d27=1.0000 nd16=1.90366 υd16=31.31
    
    
    r28=19.3000
    
        d28=6.8470 nd17=1.45650 υd17=90.27
    
    
    r29=−19.3000
    
        d29=8.2372 (wide angle edge) to 14.2351 (intermediate zoom position) to 15.0808 (telephoto edge)
    
    
    r30=−14.5534
    
        d30=0.8000 nd18=1.80610 υd18=33.27
    
    
    r31=75.8757
    
        d31=3.0000 nd19=1.92286 υd19=20.88
    
    
    r32=−19.9968
    
        d32=0.8000
    
    
    r33=∞
    
        d33=1.0000 nd20=1.51680 υd20=64.20
    
    
    r34=∞
    
        d34=4.4970 (wide angle edge) to 4.5081 (intermediate zoom position) to 4.4907 (telephoto edge)
    
    
    r35=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=344.0097,
    A=1.13202×10−5, B=−2.26973×10−8,
    C=6.79562×10−11, D=−9.81657×10−14 
    (twenty-second plane)
    K=−0.9482,
    A=−5.12429×10−6, B=−1.21508×10−7,
    C=1.69189×10−9, D=−9.91420×10−12 
    (twenty-fifth plane)
    K=−0.1842,
    A=−2.67312×10−5, B=1.32767×10−7,
    C=−9.76063×10−10, D=−4.41242×10−13
    (twenty-sixth plane)
    K=0.0482,
    A=3.21221×10−5, B=1.32020×10−7,
    C=−1.61331×10−9, D=3.26315×10−32 


FIG. 2 is a diagram of various types of aberration of the zoom lens according to the first example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 2 indicating astigmatism, represent aberration with respect to a sagittal image plane and a meridional image plane, respectively.
FIG. 3 is a cross sectional view (along the optical axis) of a zoom lens according to a second example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G21, a negative second lens group G22, a positive third lens group G23, a positive fourth lens group G24, a positive fifth lens group G25, and a negative sixth lens group G26. Further, the diaphragm STP is disposed between the second lens group G22 and the third lens group G23. The cover glass CG (or filter) is disposed between the sixth lens group G26 and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G21 includes, sequentially from the object side, a negative lens L211, a positive lens L212, a positive lens L213, and a positive lens L214. The negative lens L211 and the positive lens L212 are cemented together.
The second lens group G22 includes, sequentially from the object side, a negative lens L221, a negative lens L222, a positive lens L223, and a negative lens L224. The negative lens L222 and the positive lens L223 are cemented together. Further, a surface on the object side of the negative lens L221 is formed to be aspheric.
The third lens group G23 includes, sequentially from the object side, a positive lens L231 and a negative lens L232 that are cemented together.
The fourth lens group G24 includes, sequentially from the object side, a positive lens L241, a positive lens L242, and a negative lens L243. A surface on the object side of the positive lens L242 is aspheric. Further, the positive lens L242 and the negative lens L243 are cemented together.
The fifth lens group G25 includes, sequentially from the object side, a positive lens L251, a negative lens L252, and a positive lens L253. Both surfaces of the positive lens L251 are aspheric. Further, the negative lens L252 and the positive lens L253 are cemented together.
The sixth lens group G26 includes, sequentially from the object side, a negative lens L261 and a positive lens L262 that are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G22, the third lens group G23, and the fourth lens group G24 along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G25 along the optical axis. The first lens group G21 and the sixth lens group G26 remain fixed.
Various values related to the zoom lens according to the second example are indicated below.

    focal length of entire zoom lens=7.58 (wide angle edge) to 22.75 (intermediate zoom position) to 54.25 (telephoto edge)
    F number=2.40
    angle of view (2ω)=75.9° (wide angle edge) to 27.22° (intermediate zoom position) to 11.87° (telephoto edge)
    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=60.888
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=76.383
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=66.587
    focal length (FW) of entire optical system for infinity at wide angle edge=7.58
    (SLM−(SLW+SLT)/2)/FW=1.669
    (Values Related to Conditional Expression (2))
    F14t=−167.758
    (Values Related to Conditional Expression (3))
    deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G22=0.809
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G22=31.300
    S10/H=0.026
    r1=207.0000
    
        d1=1.6000 nd1=1.90366 υd1=31.31
    
    
    r2=68.9000
    
        d2=8.5664 nd2=1.49700 υd2=81.61
    
    
    r3=970.0000
    
        d3=0.1500
    
    
    r4=74.8900
    
        d4=6.1637 nd3=1.49700 υd3=81.61
    
    
    r5=370.0000
    
        d5=0.1500
    
    
    r6=62.6000
    
        d6=4.9877 nd4=1.75700 υd4=47.71
    
    
    r7=167.0000
    
        d7=1.0000 (wide angle edge) to 30.0775 (intermediate zoom position) to 47.5000 (telephoto edge)
    
    
    r8=442.8586 (aspheric surface)
    
        d8=0.2000 nd5=1.53920 υd5=41.21
    
    
    r9=103.6181
    
        d9=1.0000 nd6=1.88300 υd6=40.80
    
    
    r10=15.0018
    
        d10=9.0225
    
    
    r11=−24.0001
    
        d11=0.7000 nd7=1.49700 υd7=81.61
    
    
    r12=38.3759
    
        d12=5.7015 nd8=1.90366 υd8=31.31
    
    
    r13=−28.8899
    
        d13=0.5664
    
    
    r14=−24.0930
    
        d14=0.7000 nd9=1.49700 υd9=81.61
    
    
    r15=71.3234
    
        d15=55.3046 (wide angle edge) to 10.7360 (intermediate zoom position) to 3.1168 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.2000
    
    
    r17=44.5619
    
        d17=4.2309 nd10=1.61800 υd10=63.39
    
    
    r18=−20.7679
    
        d18=0.6000 nd11=1.56732 υd11=42.84
    
    
    r19=53.6764
    
        d19=4.2562 (wide angle edge) to 13.7276 (intermediate zoom position) to 1.5000 (telephoto edge)
    
    
    r20=19.4936
    
        d20=2.7141 nd12=1.84666 υd12=23.78
    
    
    r21=46.1822
    
        d21=1.4399
    
    
    r22=20.7222 (aspheric surface)
    
        d22=3.0000 nd13=1.61800 υd13=63.39
    
    
    r23=629.2796
    
        d23=0.6000 nd14=1.90366 υd14=31.31
    
    
    r24=16.2600
    
        d24=7.7197 (wide angle edge) to 6.9446 (intermediate zoom position) to 5.8651 (telephoto edge)
    
    
    r25=17.1547 (aspheric surface)
    
        d25=5.0000 nd15=1.61800 υd15=63.39
    
    
    r26=−44.7408 (aspheric surface)
    
        d26=0.1502
    
    
    r27=−125.5194
    
        d27=1.0000 nd16=1.90366 υd16=31.31
    
    
    r28=20.1000
    
        d28=8.0000 nd17=1.45650 υd17=90.27
    
    
    r29=−20.1000
    
        d29=8.2228 (wide angle edge) to 15.0177 (intermediate zoom position) to 18.5215 (telephoto edge)
    
    
    r30=−18.3070
    
        d30=0.6000 nd18=1.80610 υd18=33.27
    
    
    r31=78.3700
    
        d31=2.1531 nd19=1.92286 υd19=20.88
    
    
    r32=−25.6495
    
        d32=0.8000
    
    
    r33=∞
    
        d33=2.2000 nd20=1.51680 υd20=64.20
    
    
    r34=∞
    
        d34=5.0014 (wide angle edge) to 5.0169 (intermediate zoom position) to 4.9946 (telephoto edge)
    
    
    r35=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=−16.9314,
    A=1.77203×10−5, B=−1.88816×10−8,
    C=−1.37289×10−11, D=8.40961×10−14 
    (twenty-second plane)
    K=−0.4655,
    A=−1.30488×10−6, B=−7.35853×10−8,
    C=4.47932×10−10, D=−1.92734×10−12 
    (twenty-fifth plane)
    K=−0.1215,
    A=−2.29865×10−5, B=1.22648×10−7,
    C=−9.70568×10−10, D=1.17703×10−11 
    (twenty-sixth plane)
    K=0.7178,
    A=3.15598×10−5, B=7.93060×10−8,
    C=−7.35002×10−10, D=1.18983×10−11 


FIG. 4 is a diagram of various types of aberration of the zoom lens according to the second example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 4 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.
FIG. 5 is a cross sectional view (along the optical axis) of a zoom lens according to a third example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G31, a negative second lens group G32, a positive third lens group G33, a positive fourth lens group G34, a positive fifth lens group G35, and a negative sixth lens group G36. Further, the diaphragm STP is disposed between the second lens group G32 and the third lens group G33. The cover glass CG (or filter) is disposed between the sixth lens group G36 and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G31 includes, sequentially from the object side, a negative lens L311, a positive lens L312, a positive lens L313, and a positive lens L314. The negative lens L311 and the positive lens L312 are cemented together.
The second lens group G32 includes, sequentially from the object side, a negative lens L321, a negative lens L322, a positive lens L323, and a negative lens L324. The negative lens L322 and the positive lens L323 are cemented together. Further, a surface on the object side of the negative lens L321 is formed to be aspheric.
The third lens group G33 includes, sequentially from the object side, a positive lens L331 and a negative lens L332 that are cemented together.
The fourth lens group G34 includes, sequentially from the object side, a positive lens L341, a positive lens L342, and a negative lens L343. A surface on the object side of the positive lens L342 is aspheric. Further, the positive lens L342 and the negative lens L343 are cemented together.
The fifth lens group G35 includes, sequentially from the object side, a positive lens L351, a negative lens L352, and a positive lens L353. Both surfaces of the positive lens L351 are aspheric. Further, the negative lens L352 and the positive lens L353 are cemented together.
The sixth lens group G36 includes, sequentially from the object side, a negative lens L361 and a positive lens L362 that are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G32, the third lens group G33, and the fourth lens group G34 along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G35 along the optical axis. The first lens group G31 and the sixth lens group G36 remain fixed.
Various values related to the zoom lens according to the third example are indicated below.

    focal length of entire zoom lens=8.35 (wide angle edge) to 22.75 (intermediate zoom position) to 60.1 (telephoto edge)
    F number=2.25
    angle of view (2ω)=70.53° (wide angle edge) to 27.68° (intermediate zoom position) to 10.70° (telephoto edge)
    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=63.719
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=71.544
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=65.961
    focal length (FW) of entire optical system for infinity at wide angle edge=8.35
    (SLM−(SLW+SLT)/2)/FW=0.803
    (Values Related to Conditional Expression (2))
    F14t=−213.922
    (Values Related to Conditional Expression (3))
    deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G32=0.571
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G32=29.500
    S10/H=0.019
    r1=148.6615
    
        d1=1.6500 nd1=1.80610 υd1=33.27
    
    
    r2=61.1938
    
        d2=9.6601 nd2=1.49700 υd2=81.61
    
    
    r3=674.9250
    
        d3=0.1500
    
    
    r4=64.5400
    
        d4=6.4576 nd3=1.49700 υd3=81.61
    
    
    r5=257.1029
    
        d5=0.1500
    
    
    r6=59.8878
    
        d6=5.3883 nd4=1.61800 υd4=63.39
    
    
    r7=167.5508
    
        d7=0.9000 (wide angle edge) to 26.2588 (intermediate zoom position) to 43.4318 (telephoto edge)
    
    
    r8=306.7263 (aspheric surface)
    
        d8=0.2500 nd5=1.53610 υd5=41.00
    
    
    r9=108.4733
    
        d9=1.2000 nd6=1.88300 υd6=40.80
    
    
    r10=14.5265
    
        d10=7.8961
    
    
    r11=−25.8103
    
        d11=1.0000 nd7=1.49700 υd7=81.61
    
    
    r12=25.8103
    
        d12=5.2867 nd8=1.90366 υd8=31.31
    
    
    r13=−39.5598
    
        d13=1.3138
    
    
    r14=−24.5665
    
        d14=0.8000 nd9=1.48749 υd9=70.44
    
    
    r15=62.0539
    
        d15=47.7845 (wide angle edge) to 14.5972 (intermediate zoom position) to 3.0080 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.2000
    
    
    r17=49.1025
    
        d17=4.3624 nd10=1.61800 υd10=63.39
    
    
    r18=−16.3370
    
        d18=0.8000 nd11=1.56732 υd11=42.84
    
    
    r19=66.0271
    
        d19=1.9335 (wide angle edge) to 9.7620 (intermediate zoom position) to 4.1799 (telephoto edge)
    
    
    r20=19.0834
    
        d20=2.9583 nd12=1.84666 υd12=23.78
    
    
    r21=68.4183
    
        d21=0.1500
    
    
    r22=28.8247 (aspheric surface)
    
        d22=2.8694 nd13=1.61800 υd13=63.39
    
    
    r23=−100.6680
    
        d23=0.8000 nd14=1.90366 υd14=31.31
    
    
    r24=17.4858
    
        d24=13.3625 (wide angle edge) to 8.0360 (intermediate zoom position) to 5.8027 (telephoto edge)
    
    
    r25=17.5351 (aspheric surface)
    
        d25=5.0724 nd15=1.61800 υd15=63.39
    
    
    r26=−33.4907 (aspheric surface)
    
        d26=1.2961
    
    
    r27=−97.1180
    
        d27=1.0000 nd16=1.90366 υd16=31.31
    
    
    r28=18.8323
    
        d28=7.7198 nd17=1.45650 υd17=90.27
    
    
    r29=−18.8323
    
        d29=8.3857 (wide angle edge) to 13.7122 (intermediate zoom position) to 15.9455 (telephoto edge)
    
    
    r30=−14.8301
    
        d30=0.8000 nd18=1.80610 υd18=33.27
    
    
    r31=875.2519
    
        d31=3.0000 nd19=1.92286 υd19=20.88
    
    
    r32=−19.0866
    
        d32=0.5000
    
    
    r33=∞
    
        d33=1.0000 nd20=1.51680 υd20=64.20
    
    
    r34=∞
    
        d34=4.4800 (wide angle edge) to 4.5124 (intermediate zoom position) to 4.4780 (telephoto edge)
    
    
    r35=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=326.5969,
    A=1.45864×10−5, B=−3.27413×10−8,
    C=8.21551×10−11, D=−1.78052×10−13 
    (twenty-second plane)
    K=−1.0471,
    A=−6.42643×10−6, B=−5.52441×10−8,
    C=4.13340×10−10, D=−1.57709×10−12 
    (twenty-fifth plane)
    K=−0.1413,
    A=−2.40303×10−5, B=1.28161×10−7,
    C=−1.08450×10−9, D=3.69783×10−12 
    (twenty-sixth plane)
    K=0.1817,
    A=3.28626×10−5, B=1.15663×10−7,
    C=−1.39748×10−9, D=5.65410×10−12 


FIG. 6 is a diagram of various types of aberration of the zoom lens according to the third example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 6 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.
FIG. 7 is a cross sectional view (along the optical axis) of a zoom lens according to a fourth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G41, a negative second lens group G42, a positive third lens group G43, a positive fourth lens group G44, and a positive fifth lens group G45. Further, the diaphragm STP is disposed between the second lens group G42 and the third lens group G43. The cover glass CG (or filter) is disposed between the fifth lens group G45 and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G41 includes, sequentially from the object side, a negative lens L411, a positive lens L412, a positive lens L413, and a positive lens L414. The negative lens L411 and the positive lens L412 are cemented together.
The second lens group G42 includes, sequentially from the object side, a negative lens L421, a negative lens L422, a positive lens L423, and a negative lens L424. The positive lens L423 and the negative lens L424 are cemented together. Further, a surface on the object side of the negative lens L421 is aspheric.
The third lens group G43 includes, sequentially from the object side, a positive lens L431 and a negative lens L432 that are cemented together.
The fourth lens group G44 includes, sequentially from the object side, a positive lens L441, a positive lens L442, and a negative lens L443. A surface on the object side of the positive lens L442 is aspheric. Further, the positive lens L442 and the negative lens L443 are cemented together.
The fifth lens group G45 includes, sequentially from the object side, a positive lens L451, a negative lens L452, and a positive lens L453. Both surfaces of the positive lens L451 are aspheric. Further, the negative lens L452 and the positive lens L453 are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G42 and the fourth lens group G44 along the optical axis. At this time, the diaphragm STP is also moved. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G45 along the optical axis. The first lens group G41 and the third lens group G43 remain fixed.
Various values related to the zoom lens according to the fourth example are indicated below.

    focal length of entire zoom lens=8.14 (wide angle edge) to 22.75 (intermediate zoom position) to 60.60 (telephoto edge) F number=2.85


angle of view (2ω)=72.42° (wide angle edge) to 27.47° (intermediate zoom position) to 10.66° (telephoto edge)

    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=58.376
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=65.379
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=58.356
    focal length (FW) of entire optical system for infinity at wide angle edge=8.14
    (SLM−(SLW+SLT)/2)/FW=0.861
    (Values Related to Conditional Expression (2))
    F14t=−218.45
    (Values Related to Conditional Expression (3))
    deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G42=0.307
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G42=27.420
    S10/H=0.011
    r1=319.7966
    
        d1=1.6500 nd1=1.90366 υd1=31.31
    
    
    r2=72.5656
    
        d2=10.7848 nd2=1.49700 υd2=81.61
    
    
    r3=−311.7970
    
        d3=0.1497
    
    
    r4=64.5319
    
        d4=7.9428 nd3=1.49700 υd3=81.61
    
    
    r5=517.6623
    
        d5=0.1504
    
    
    r6=62.9561
    
        d6=4.8145 nd4=1.83481 υd4=42.72
    
    
    r7=125.2065
    
        d7=1.0515 (wide angle edge) to 28.3835 (intermediate zoom position) to 46.0511 (telephoto edge)
    
    
    r8=202.1496 (aspheric surface)
    
        d8=0.3000 nd5=1.53610 υd5=41.20
    
    
    r9=158.8874
    
        d9=1.2000 nd6=1.88300 υd6=40.80
    
    
    r10=13.6525
    
        d10=7.7684
    
    
    r11=−22.2902
    
        d11=0.8000 nd7=1.49700 υd7=81.61
    
    
    r12=28.9611
    
        d12=1.8315
    
    
    r13=34.0302
    
        d13=5.2187 nd8=1.88300 υd8=40.80
    
    
    r14=−27.8585
    
        d14=0.7997 nd9=1.49700 υd9=81.61
    
    
    r15=85.7544
    
        d15=47.1745 (wide angle edge) to 12.8409 (intermediate zoom position) to 2.1755 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.0013 (wide angle edge) to 10.0026 (intermediate zoom position) to 3.0001 (telephoto edge)
    
    
    r17=48.7738
    
        d17=1.4336 nd10=1.72916 υd10=54.67
    
    
    r18=−150.0000
    
        d18=0.8000 nd11=1.64769 υd11=33.84
    
    
    r19=52.3545
    
        d19=5.1946 (wide angle edge) to 3.0000 (intermediate zoom position) to 2.00334 (telephoto edge)
    
    
    r20=16.0966
    
        d20=2.1227 nd12=1.84666 υd12=23.78
    
    
    r21=51.9417
    
        d21=0.1500
    
    
    r22=20.9928 (aspheric surface)
    
        d22=3.0358 nd13=1.61800 υd13=63.39
    
    
    r23=−54.8038
    
        d23=1.4774 nd14=1.90366 υd14=31.31
    
    
    r24=12.8327
    
        d24=8.0538 (wide angle edge) to 6.4772 (intermediate zoom position) to 7.0282 (telephoto edge)
    
    
    r25=16.9803 (aspheric surface)
    
        d25=4.8893 nd15=1.61800 υd15=63.39
    
    
    r26=−38.2034 (aspheric surface)
    
        d26=0.1499
    
    
    r27=−101.4054
    
        d27=0.8000 nd16=1.90366 υd16=31.31
    
    
    r28=22.1937
    
        d28=7.0000 nd17=1.45650 υd17=90.27
    
    
    r29=−19.4717
    
        d29=13.2585 (wide angle edge) to 17.0370 (intermediate zoom position) to 17.4265 (telephoto edge)
    
    
    r30=∞
    
        d30=2.0000 nd18=1.51680 υd18=64.20
    
    
    r31=∞
    
        d31=5.0092 (wide angle edge) to 5.0029 (intermediate zoom position) to 5.0090 (telephoto edge)
    
    
    r32=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=−475.5474,
    A=2.30384×10−5, B=−9.02107×10−8,
    C=2.44012×10−10, D=−3.43957×10−13 
    (twenty-second plane)
    K=−0.1382,
    A=3.54823×10−6, B=−7.49188×10−8,
    C=1.47759×10−9, D=−1.06171×10−11 
    (twenty-fifth plane)
    K=−0.2034,
    A=−2.79047×10−5, B=9.40720×10−8,
    C=−2.20786×10−9, D=1.32509×10−11 
    (twenty-sixth plane)
    K=−0.7196,
    A=3.44659×10−5, B=−1.31505×10−8,
    C=−1.47468×10−9, D=1.07727×10−11 


FIG. 8 is a diagram of various types of aberration of the zoom lens according to the fourth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 8 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.
FIG. 9 is a cross sectional view (along the optical axis) of a zoom lens according to a fifth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G51, a negative second lens group G52, a positive third lens group G53, a positive fourth lens group G54, and a positive fifth lens group G55. Further, the diaphragm STP is disposed between the second lens group G52 and the third lens group G53. The cover glass CG (or filter) is disposed between the fifth lens group G55 and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G51 includes, sequentially from the object side, a negative lens L511, a positive lens L512, a positive lens L513, and a positive lens L514. The negative lens L511 and the positive lens L512 are cemented together.
The second lens group G52 includes, sequentially from the object side, a negative lens L521, a negative lens L522, a positive lens L523, and a negative lens L524. The positive lens L523 and the negative lens L524 are cemented together. Further, a surface on the object side of the negative lens L521 is aspheric.
The third lens group G53 includes, sequentially from the object side, a positive lens L531 and a negative lens L532 that are cemented together.
The fourth lens group G54 includes, sequentially from the object side, a positive L541, a positive lens L542, and a negative lens L543. A surface on the object side of the positive lens L542 is aspheric. Further, the positive lens L542 and the negative lens L543 are cemented together.
The fifth lens group G55 includes, sequentially from the object side, a positive lens L551, a negative lens L552, and a positive lens L553. Both surfaces of the positive lens L551 are aspheric. Further, the negative lens L552 and the positive lens L553 are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G52, the third lens group G53, and the fourth lens group G54 along the optical axis. Furthermore, zooms lens corrects imaging plane (image location) variation accompanying zoom and focuses the image, by moving the fifth lens group G55 along the optical axis. The first lens group G51 remains fixed.
Various values related to the zoom lens according to the fifth example are indicated below.

    focal length of entire zoom lens=7.80 (wide angle edge) to 22.75 (intermediate zoom position) to 58.04 (telephoto edge)
    F number=2.85
    angle of view (2ω)=74.29° (wide angle edge) to 27.90° (intermediate zoom position) to 11.22° (telephoto edge)
    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=53.038
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=63.160
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=54.477
    focal length (FW) of entire optical system for infinity at wide angle edge=7.80
    (SLM−(SLW+SLT)/2)/FW=1.205
    (Values Related to Conditional Expression (2))
    F14t=−222.24
    (Values Related to Conditional Expression (3)) deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G52=0.354
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G52=29.700
    S10/H=0.012
    r1=282.5658
    
        d1=1.6500 nd1=1.90366 υd1=31.31
    
    
    r2=71.7229
    
        d2=11.1441 nd2=1.49700 υd2=81.61
    
    
    r3=−269.6826
    
        d3=0.1500
    
    
    r4=58.2686
    
        d4=7.4164 nd3=1.49700 υd3=81.61
    
    
    r5=258.2745
    
        d5=0.1500
    
    
    r6=60.2403
    
        d6=4.2271 nd4=1.88300 υd4=40.80
    
    
    r7=101.8945
    
        d7=0.9000 (wide angle edge) to 27.8306 (intermediate zoom position) to 45.9000 (telephoto edge)
    
    
    r8=111.4890 (aspheric surface)
    
        d8=0.3000 nd5=1.53610 υd5=41.20
    
    
    r9=93.8724
    
        d9=1.2000 nd6=1.88300 υd6=40.80
    
    
    r10=13.2527
    
        d10=8.8423
    
    
    r11=−21.3522
    
        d11=0.8000 nd7=1.49700 υd7=81.61
    
    
    r12=28.9461
    
        d12=1.2651
    
    
    r13=31.9998
    
        d13=5.6440 nd8=1.88300 υd8=40.80
    
    
    r14=−28.3373
    
        d14=0.8000 nd9=1.49700 υd9=81.61
    
    
    r15=80.7396
    
        d15=48.6273 (wide angle edge) to 11.5723 (intermediate zoom position) to 2.1726 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.0000
    
    
    r17=90.9268
    
        d17=1.6008 nd10=1.77250 υd10=49.62
    
    
    r18=−50.0000
    
        d18=0.8000 nd11=1.62004 υd11=36.30
    
    
    r19=82.9067
    
        d19=1.5000 (wide angle edge) to 7.2696 (intermediate zoom position) to 1.5000 (telephoto edge)
    
    
    r20=15.4903
    
        d20=2.1378 nd12=1.84666 υd12=23.78
    
    
    r21=33.7883
    
        d21=0.1500
    
    
    r22=16.2526 (aspheric surface)
    
        d22=2.9662 nd13=1.61800 υd13=63.39
    
    
    r23=−104.1231
    
        d23=1.4133 nd14=1.90366 υd14=31.31
    
    
    r24=11.8086
    
        d24=8.4563 (wide angle edge) to 8.2596 (intermediate zoom position) to 5.9201 (telephoto edge)
    
    
    r25=16.0302 (aspheric surface)
    
        d25=5.7946 nd15=1.61800 υd15=63.39
    
    
    r26=−38.5894 (aspheric surface)
    
        d26=0.1500
    
    
    r27=−113.2219
    
        d27=0.8000 nd16=1.90366 υd16=31.31
    
    
    r28=22.6876
    
        d28=6.0000 nd17=1.45650 υd17=90.27
    
    
    r29=−20.1597
    
        d29=11.2692 (wide angle edge) to 15.8183 (intermediate zoom position) to 15.2442 (telephoto edge)
    
    
    r30=∞
    
        d30=2.0000 nd18=1.51680 υd18=64.20
    
    
    r31=∞
    
        d31=5.0000
    
    
    r32=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=−137.2586,
    A=2.62265×10−5, B=−9.31163×10−8,
    C=2.21275×10−10, D=−2.81522×10−13 
    (twenty-second plane)
    K=−0.0855,
    A=5.22861×10−6, B=−6.95276×10−8,
    C=1.84884×10−9, D=−1.44193×10−11 
    (twenty-fifth plane)
    K=−0.2776,
    A=−3.12577×10−5, B=8.20931×10−8,
    C=−1.91427×10−9, D=1.61775×10−11 
    (twenty-sixth plane)
    K=−0.6048,
    A=3.43639×10−5, B=−7.14301×10−9,
    C=−1.47690×10−9, D=1.55904×10−11 


FIG. 10 is a diagram of various types of aberration of the zoom lens according to the fifth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 10 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.
FIG. 11 is a cross sectional view (along the optical axis) of a zoom lens according to a sixth example. The zoom lens includes, sequentially from the object side (not depicted), a positive first lens group G61, a negative second lens group G62, a positive third lens group G63, a positive fourth lens group G64, a positive fifth lens group G65, and a negative sixth lens group G66. Further, the diaphragm STP is disposed between the second lens group G62 and the third lens group G63. The cover glass CG (or filter) is disposed between the sixth lens group G66 and the imaging plane IMG. The cover glass CG (or filter) is disposed as needed and may be omitted when not necessary. Further, at the imaging plane IMG, the optical receiving surface of an imaging element such as a CCD, a CMOS, etc. is disposed.
The first lens group G61 includes, sequentially from the object side, a negative lens L611, a positive lens L612, a positive lens L613, and a positive lens L614. The negative lens L611 and the positive lens L612 are cemented together.
The second lens group G62 includes, sequentially from the object side, a negative lens L621, a negative lens L622, a positive lens L623, and a negative lens L624. The negative lens L622 and the positive lens L623 are cemented together. Further, a surface on the object side of the negative lens L621 is aspheric.
The third lens group G63 includes, sequentially from the object side, a positive lens L631 and a negative lens L632 that are cemented together.
The fourth lens group G64 includes, sequentially from the object side, a positive L641, a positive lens L642, and a negative lens L643. A surface on the object side of the positive lens L642 is aspheric. Further, the positive lens L642 and the negative lens L643 are cemented together.
The fifth lens group G65 includes, sequentially from the object side, a positive lens L651, a negative lens L652, and a positive lens L653. Both surfaces of the positive lens L651 are aspheric. Further, the negative lens L652 and the positive lens L653 are cemented together.
The sixth lens group G66 includes, sequentially from the object side, a negative lens L661 and a positive lens L662 that are cemented together.
The zoom lens zooms from the wide angle edge to the telephoto edge by moving the second lens group G62 and the third lens group G63 along the optical axis. Furthermore, the zoom lens corrects imaging plane (image location) variation accompanying zoom, by moving the fifth lens group G65 along the optical axis. The first lens group G61, the fourth lens group G64, and the sixth lens group G66 remain fixed.
Various values related to the zoom lens according to the sixth example are indicated below.

    focal length of entire zoom lens=8.38 (wide angle edge) to 22.75 (intermediate zoom position) to 62.39 (telephoto edge)
    F number=2.85
    angle of view (2ω)=70.28° (wide angle edge) to 27.57° (intermediate zoom position) to 10.30° (telephoto edge)
    (Values Related to Conditional Expression (1))
    distance (SLW) from diaphragm STP at wide angle edge to imaging plane IMG=63.190
    distance (SLM) from diaphragm STP at intermediate zoom position to imaging plane IMG=74.408
    distance (SLT) from diaphragm STP at telephoto edge to imaging plane IMG=62.659
    focal length (FW) of entire optical system for infinity at wide angle edge=8.38
    (SLM−(SLW+SLT)/2)/FW=1.370
    (Values Related to Conditional Expression (2))
    F14t=−265.26
    (Values Related to Conditional Expression (3))
    deviation (S10) of paraxial curvature radius and aspheric shape at height that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G62=0.544
    height (H) that is 100% of effective diameter of aspheric surface on object side of lens that is farthest on object side in second lens group G62=30.100
    S10/H=0.018
    r1=138.8718
    
        d1=1.6500 nd1=1.80610 υd1=33.27
    
    
    r2=61.9153
    
        d2=8.5663 nd2=1.49700 υd2=81.61
    
    
    r3=1028.2950
    
        d3=0.1500
    
    
    r4=60.3545
    
        d4=6.3671 nd3=1.49700 υd3=81.61
    
    
    r5=295.8558
    
        d5=0.1500
    
    
    r6=65.2190
    
        d6=4.1407 nd4=1.61800 υd4=63.39
    
    
    r7=139.5672
    
        d7=0.9000 (wide angle edge) to 25.2786 (intermediate zoom position) to 44.9569 (telephoto edge)
    
    
    r8=262.0586 (aspheric surface)
    
        d8=0.3000 nd5=1.53610 υd5=41.21
    
    
    r9=138.6589
    
        d9=1.2000 nd6=1.88300 υd6=40.80
    
    
    r10=16.2318
    
        d10=7.7691
    
    
    r11=−26.5932
    
        d11=1.0000 nd7=1.49700 υd7=81.61
    
    
    r12=26.5932
    
        d12=5.5008 nd8=1.90366 υd8=31.31
    
    
    r13=−36.2017
    
        d13=1.2996
    
    
    r14=−23.2275
    
        d14=0.8000 nd9=1.48749 υd9=70.44
    
    
    r15=38.1766
    
        d15=47.0041 (wide angle edge) to 11.4261 (intermediate zoom position) to 3.4734 (telephoto edge)
    
    
    r16=∞ (diaphragm)
    
        d16=3.2000
    
    
    r17=47.7891
    
        d17=3.0763 nd10=1.61800 υd10=63.39
    
    
    r18=−16.0874
    
        d18=0.8000 nd11=1.56732 υd11=42.84
    
    
    r19=96.4756
    
        d19=4.7246 (wide angle edge) to 15.9240 (intermediate zoom position) to 4.1984 (telephoto edge)
    
    
    r20=18.3644
    
        d20=2.4991 nd12=1.84666 υd12=23.78
    
    
    r21=59.3603
    
        d21=0.1500
    
    
    r22=28.9811 (aspheric surface)
    
        d22=2.6325 nd13=1.61800 υd13=63.39
    
    
    r23=−104.8188
    
        d23=0.8000 nd14=1.90366 υd14=31.31
    
    
    r24=16.9149
    
        d24=12.7613 (wide angle edge) to 6.7184 (intermediate zoom position) to 5.8228 (telephoto edge)
    
    
    r25=17.1503 (aspheric surface)
    
        d25=6.1084 nd15=1.61800 υd15=63.39
    
    
    r26=−34.1345 (aspheric surface)
    
        d26=0.1538
    
    
    r27=−111.6006
    
        d27=1.0000 nd16=1.90366 υd16=31.31
    
    
    r28=19.4748
    
        d28=6.9286 nd17=1.45650 υd17=90.27
    
    
    r29=−19.4749
    
        d29=8.2678 (wide angle edge) to 14.3106 (intermediate zoom position) to 15.2062 (telephoto edge)
    
    
    r30=−14.0575
    
        d30=0.8000 nd18=1.80610 υd18=33.27
    
    
    r31=160.0140
    
        d31=3.0000 nd19=1.92286 υd19=20.88
    
    
    r32=−18.9554
    
        d32=2.2900
    
    
    r33=∞
    
        d33=1.0000 nd20=1.51680 υd20=64.20
    
    
    r34=∞
    
        d34=2.9983 (wide angle edge) to 3.0167 (intermediate zoom position) to 2.9932 (telephoto edge)
    
    
    r35=∞ (imaging plane)
    constant of cone (K) and aspheric coefficients (A, B, C, D)
    (eighth plane)
    K=235.8261,
    A=9.85751×10−6, B=−1.48380×10−8,
    C=2.78366×10−11, D=−3.08842×10−14 
    (twenty-second plane)
    K=−0.8891,
    A=−4.81420×10−6, B=−1.21584×10−7,
    C=1.73658×10−9, D=−1.08127×10−11 
    (twenty-fifth plane)
    K=−0.1835,
    A=−2.65316×10−5, B=1.26633×10−7,
    C=−1.04068×10−9, D=−1.23932×10−12 
    (twenty-sixth plane)
    K=0.4017,
    A=3.09450×10−5, B=1.21550×10−7,
    C=−1.69140×10−9, D=2.67818×10−12 


FIG. 12 is a diagram of various types of aberration of the zoom lens according to the sixth example. In the diagram “g”, “d”, and “c” respectively represent aberrations for wavelengths corresponding to g-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). ΔS and ΔM, in a portion of FIG. 12 indicating astigmatism, represent aberration with respect to the sagittal image plane and the meridional image plane, respectively.
Among the values for each of the examples above, r1, r2, . . . indicate radii of curvature for each lens, diaphragm surface, etc.; d1, d2, . . . indicate the thickness of the lenses, diaphragm, etc. or the distance between surfaces thereof; nd1, nd2, . . . indicates the refraction index of each lens with respect to the d-line (λ=587.56 nm); υd1, υd2, . . . indicates the Abbe number with respect to the d-line (λ=587.56 nm) of each lens.
Each of the aspheric surfaces above can be expressed by equation [1], where Z=the depth of the aspheric surface, y=the height from the optical axis, and the direction of travel of light is positive.




  
    
      
        Z
        =
        
          
            
              y
              2
            
            
              
                R
                ⁡
                
                  (
                  
                    1
                    +
                    
                      
                        1
                        +
                        
                          
                            (
                            
                              1
                              +
                              K
                            
                            )
                          
                          ⁢
                          
                            y
                            /
                            
                              R
                              2
                            
                          
                        
                      
                    
                  
                  )
                
              
              2
            
          
          +
          
            Ay
            4
          
          +
          
            By
            6
          
          +
          
            Cy
            8
          
          +
          
            Dy
            10
          
        
      
    
    
      
        [
        1
        ]
      
    
  




And where, R is paraxial radii of curvature; K is constant of the cone; and A, B, C, D are the fourth, sixth, eighth, and tenth aspheric coefficients, respectively.
As described above, the zoom lens according to each of the examples above satisfies conditional expressions (1) and (2), whereby diameter reduction, a wide angle of view (70° or more), and maintenance of the F number at a constant value or below (2.9 or less) over the entire zoom range is achieved, making the zoom lens a large diameter zoom lens that is capable of high zoom rations (6 or more). Further, by forming a surface on the object side of the lens farthest on the object side in the second lens group, to be an aspheric surface that satisfies conditional expression (3) above, various types of aberration can be effectively corrected over the entire zoom range without sacrificing the compactness of the optical system.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.

## Claims

1. A zoom lens comprising, sequentially from an object side:
a positive first lens group;
a negative second lens group;
a diaphragm;
a positive third lens group;
a positive fourth lens group; and
a positive fifth lens group, wherein

a first condition 0.8≦(SLM−(SLW+SLT)/2)/FW≦2.0 and a second condition F14t≦0 are satisfied, SLW being a distance from the diaphragm at a wide angle edge to an imaging plane, SLM being a distance from the diaphragm at an intermediate zoom position to the imaging plane, SLT being a distance from the diaphragm at a telephoto edge to the imaging plane, FW being optical system focal length for infinity at the wide angle edge, and F14t being a combined focal length for the first to the fourth lens groups at the telephoto edge.

2. The zoom lens according to claim 1, wherein:
in the second lens group, a lens farthest on the object side among lenses in the second lens group, has on the object side, an aspheric surface satisfying a third condition S10/H≧0.005, S10 being deviation of paraxial curvature radius and aspheric shape at a height that is 100% of an effective diameter of the aspheric surface and H being the height of 100% of the effective diameter of the aspheric surface.