JPH03233422A - Small-sized zoom lens - Google Patents

Abstract

PURPOSE:To obtain this zoom lens which has small fluctuation in chromatic aberration of magnification attending on zooming by specifying the focal lengths of respective groups and the Abbe numbers of 2nd and 3rd lenses in a 3rd group. CONSTITUTION:A 1st group I has a negative focal length f1, a 2nd group II has a positive focal length f2, and the 3rd group III has a negative focal length f3; and the 1st - 3rd groups I - III move toward an object while varying in mutual interval to carry out the variable magnification from the wide-angle side to the telephoto side. When the focal length of the whole system on the object side is denoted as fw, the conditions shown by inequalities I - III are satisfied with f1 - f3 and fw. Then the conditions of nu3N > nu3P are satisfied where nu3N is the Abbe number of the 2nd negative lens in the 3rd group III and nu3P is the Abbe number of the 3rd positive lens. Consequently, the chromatic aberration of the magnification of the 3rd group is compensated and the fluctuation in the chromatic aberration of the magnification of the whole system attending on zooming can be suppressed small.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a compact zoom lens.

[Prior Art] As a zoom lens with a high variable power ratio of about 3, a zoom lens with a negative, positive, and negative three group configuration is known. [Problems to be Solved by the Invention] This zoom lens has the following problems: There is a problem in that the chromatic aberration of magnification is large.

An object of the present invention is to provide a compact zoom lens that has a negative, positive, and negative three-group structure and has small fluctuations in chromatic aberration of magnification due to zooming.

[Means for Solving the Problems] Hereinafter, as shown in FIG. 1, the compact zoom lens of claim 1.2 which characterizes the present invention will be described from the object side (left side in FIG. 1) to the image side (right side in the same figure). A first group (2), a second group (IL), and a third group (III) are arranged in this order toward each other.

The first group has a negative focal length f1, the second group II has a positive focal length f2, and the third group III has a negative focal length f3.
has. and 1st to 3rd groups I, II, III
By moving toward the object side while changing the distance between them, the magnification is changed from the wide-angle side to the telephoto side.

When the focal length of the entire system at the wide-angle end is rW, as above, f1, f2, f3 and fw are (1) 0.3<1f
31/1f11<1.0(it) 1.2<1f
il/fw < 2.3 (iii) 0.9 < 1
The difference between the zoom lens according to claim 1.2, which is characterized by the condition f31/fw < 1.4, lies in the specific lens configuration of the third group.

That is, in the zoom lens according to claim 1, the third group III has a positive lens, a negative lens, and a positive lens arranged in this order from the object side to the image side, and the second lens is a negative lens, and the third lens is a negative lens. It is constructed by cementing a positive lens which is a lens of In addition, when the Abbe number of the negative lens that is the second lens in the third group III is ν3N% and the Abbe number of the positive lens that is the third lens is ν3P, these ν3
In the zoom lens according to claim 2, in which Nf ν3P is characterized by the following condition: (iv) ν3N>ν3P, the third group III includes a positive lens, a negative lens, a positive lens, and a negative lens in this order from the object side to the image side. The second lens, which is a negative lens, and the third lens, which is a positive lens, are cemented together. In addition, when the Abbe number of the second negative lens in the third group III is ν3N% and the Atsube number of the third positive lens is ν3P, these , N, and ν3P are As with the zoom lens in item 1,
The above condition (iv) is satisfied.

[Function] A negative first lens group is placed in front of the second lens group, which is a positive master lens group, and the first lens group is placed in front of the second lens group, which is a positive master lens group, and the first lens group is placed in front of the second lens group, which is a positive master lens group. By changing the interval between the second groups, the apparent diameter of the diaphragm of the master lens group, that is, the entrance pupil diameter, can be changed as the magnification is changed, making it possible to reduce the FNO during telephoto. At the wide-angle end, the first group and the second group are separated, but since the first group is a negative lens system, an increase in lens diameter is suppressed.

The negative first group and the positive second group constitute a retrofocus type two-group zoom system suitable for wide angles, and are responsible for part of zooming.

A composite system consisting of a negative first group and a second group with a negative lateral magnification has a positive focal length, and by following these with a negative third group, the entire system constitutes a telephoto type. be able to. This configuration allows the entire zoom lens to be made more compact.

Also, when changing the magnification from wide-angle to telephoto, the third group is used as the first and second group.
By rapidly approaching the synthetic threads of the group, it is possible to greatly change the lateral magnification and increase the variable power ratio.

The distance between the principal points of the first group and the second group is d12, the distance between the third group and the image plane, that is, the back focus is bfW, the focal length of the entire system is f, and the refractive powers of the first to third groups are each φ1 (=1
/f1), φ2 (three 1/f2), φ3 (three 1/f3),
If the refractive power of the entire system is φ (=1/f), then φ3・(1/bf) [1−(1/φ)(φ+(1d+
2φ2)+φ2)], and under the condition of d+2<1/φ2, φ3 and φ1 are inversely proportional.

Condition (i) is based on this relationship. This defines the relationship between the third lens group, and if the upper limit is exceeded, the compactness will be lost during telephoto operation, and if the lower limit is exceeded, the FNO during telephoto operation will become larger.

Conditions (ii) and (iii) are conditions (i) and (7) that place limits on fW and f3, and when the upper limit of condition (ii) is exceeded, the effect of making the first group negative fades; FN at telephoto
As O increases, the first. Since the combined refractive power of the second group increases and the lateral magnification of the third group increases, the amount of movement of the third group increases with zooming, making it difficult to maintain a sufficient distance between the groups during telephoto.

Moreover, if the lower limit of condition (ii) is exceeded, the second. Third
The distance between the groups increases, and the diameter of the third group increases, or the amount of peripheral light decreases.

If the upper limit of condition (iii) is exceeded, the telephoto property will decrease and the compactness of the system will be lost; if the lower limit is exceeded, the Petzval sum of the entire system will become small, making it difficult to obtain an appropriate image surface with a balance between the center and the periphery. It becomes difficult.

In order to achieve efficient zooming in the present invention, both the zoom lens of claim 1.2 and the following condition (V
), (iV) is desirable.

That is, the first one at wide-angle. The principal point interval d1□ of the second group, the second. The principal point interval d23W of the third group is (v)
d1zw/fz < 1(Vl) dz3W
/fw < 0.85.

Condition (v) is the first condition at wide-angle. This means that the second group interval is set to a certain value or more. This condition is related to the refractive power of the third group.

1st. If the wide-angle refractive power of the second group of synthetic threads is φ1□1, and the back focus is bfW, and the wide-angle refractive power of the entire system is φ, then between these, f: + l□ 1bfW/ [1 −((φ1+φ2
There is the following relationship: d12Wφ□φ2)/φ1).

In a system that effectively contributes to shortening the entire system by shortening the back focus, r31 becomes smaller when bfW is reduced. However, if d1□ increases beyond the range of condition (V), 1f31 becomes even smaller, making it difficult to maintain the Petzval sum of the entire system appropriately. There also arises the problem that the diameter of the I-th group becomes large when the lens is wide-angle.

Condition (vi) is the second condition at wide-angle. This specifies the distance between the third group, and when it goes out of the condition range, the ray height of the third group increases, and the third group
Either the diameter of the group becomes large or the amount of peripheral light is insufficient.

Since the present invention covers a variable power range from a wide angle with a half angle of view of about 31 degrees to a variable power ratio of about 3, the amount of movement of the third group toward the object side when zooming from wide angle to telephoto is large. Therefore, if the chromatic aberration of magnification of the third group is insufficiently corrected, the chromatic aberration of magnification due to zooming will fluctuate greatly and the performance will deteriorate.

Therefore, in the zoom lens of claim 1, the third group is composed of three lenses, positive, negative, and positive, in order from the object side, and the second lens is a negative lens, and the third lens is a positive lens. They were laminated together to form a cemented lens, and the magnitude relationship of the Abbe numbers ν3N and ν3P of the negative lens and positive lens in this cemented lens was defined as condition (iv).

In the zoom lens of claim 2, the third group is composed of four lenses, positive, negative, positive, and negative, in order from the object side, and the second lens is a negative lens, and the third lens is a positive lens. are laminated together to form a cemented lens, and the magnitude relationship of the Abbe numbers ν3N and ν3P of the negative lens and positive lens in this cemented lens is defined as condition (iv).

By satisfying condition (iv), it becomes possible to correct the positive magnification chromatic aberration that tends to occur in the third group, which has a large negative power, and suppresses fluctuations in the magnification chromatic aberration of the entire system due to zooming. be able to.

In the zoom lens of claim 1, among the three lenses constituting the third group, only one negative lens is the second lens in the group, so the object side surface of this negative lens is a surface with a small radius of curvature. As a result, the amount of higher-order aberrations generated increases. Therefore, the third
The object-side surface of the negative lens in the group is preferably an aspheric surface whose curvature becomes gentler as it moves away from the optical axis.

Furthermore, in both the zoom lenses of claims 1 and 2, the first group is composed of negative and positive lenses from the object side, and the negative lens has an Abbe number ν.
It is desirable that 1N and the Abbe number ν1P of the positive lens satisfy the following condition: (vii) shi, N−shi1p>17. By satisfying this condition, it becomes possible to correct axial and lateral chromatic aberrations in the first group, and it also becomes possible to correct various political differences.

[Example code] Specific examples will be given below.

In each embodiment, the radius of curvature of the i-th surface (including the aperture surface) counted from the object side is r8, and the distance between the i-th and i+1-th surfaces on the optical axis is d. In addition, the refractive index and Atsube number for the d-line of the j-th lens counting from the object side are respectively set as n1ν, and the composite focal length of the entire system is set as f.
Let one angle of view be ω (degrees).

First, two embodiments of the compact zoom lens according to claim 1 will be described. The lens configurations of these two examples are as shown in FIGS. 2 and 3. In the "aspherical surface" adopted in Example 1.2, Y is the coordinate axis perpendicular to the optical axis, 2 is the coordinate axis in the optical axis direction, r is the radius of curvature on the optical axis, and A, B, and C are As a higher-order aspheric coefficient, Z-(1/r)/[1+(1-(
This is a curved surface obtained by rotating the curve 1/r")Y2)"2]+AY'+BY'10Y8 around the optical axis. In Examples 1 and 2, an asterisk (*) is attached to the aspherical surface to represent the aspherical surface, and the aspherical coefficient A,
Specify the aspherical shape by giving B and C. In the display of aspherical coefficients, "powers" are represented by (E numbers). For example, if you read E-8, this symbol means 10-8, and this value is multiplied by the number before it.

Example 1 f: 36-102. FNo=3P23~7.70. ω=
63P4~23P91 rld+ J
nJl'j1 -63P377 1.400 1
1.75500 52.32 23P404 1.
140 3 25.115 4.590 2 1.6476
9 33P84 1765.771 Variable 5 21.326 3P520 3 1.7130
0 53P96 -40.733 0.700 4
1.84666 23P87 -70.732
0.900 3 co (aperture) 0.8009 17.5
40 2.080 5 1.58384 80.81
0 65.528 0.810 11 -41.120 3P700 6 1.834
00 37.312 15.319 2.400 13 32.276 2.560 7 1.563
84 60.814 -21.358 Variable 15 -31.459 4.260 8 1.
58144 40.816" -15,7713,4
99 17" -12,9792,17491,80420
46,51877,5356,256101,6989
530,019” -50,846 Aspherical surface (16th surface) A=9.244601E-6, B=1.594573E
-7, C=-1,715580E-9 Aspherical surface (17th surface) A=2.604209E-5, B=1.496540E
-7, C=-1, 165835E-11 aspherical surface (19th
surface) A=4.551905E-7, B=-8,629262
E-9, C = 2.035120E-11 variable amount f 36 60.597 102d
413P144 8.223 0.293d,
412.989 3P897 0.919 Condition value f3V1f11=0.686, IfW l/fw=
1.583P If31/fW=1.085 Also, the condition values for conditions (v) to (vii) that are desirable to satisfy are: dx2w/fz"o-858, d23w/fw"o,
809. SIIN-SI, p"18-5.

FIG. 2 shows the lens arrangement of Example 1 at the wide-angle end.

Example 2 f=36-102. FNo=3P23~7.7. ω:6
3P6~23P9ir,
d, J n−ν J
l -63,0831,40011,755005
2,3224,3541,140 325,7964,59021,8476933,84
827,455 variable 5 21.205 3P520 3 1.7130
0 53P96 -42.520 0.700 4
1.84666 23P87 -77.129
0.900 8 ■(Aperture) o, go.

9 17.643 2.080 5 1.5638
4 60.810 74.787 0.810 11 -40-770 3P700 6 1.834
00 3'1312 15.448 2.400 13 33P403 2.560 7 1.563
84 60.814 -21.094 Variable 15 -29.037 4.098 8 1.
58144 40.918" -15,5643,5
72 17” -13,1292,17491,80420
46,5181666,8603,316101,84
68623,819-61,090 Aspherical surface (16th surface) A=9.742750E-6, B=1.931299E
-7, C=-1,966416E-9 Aspherical surface (F-th surface) A2 2.084409E-5, B=2.096973E
-7,C=-6,287805E-10 variable amount f 36 60.597 102d
413P230 8.310 0.379d,
412.266 3P194 0.215 Condition value f3t/1f11=0.686, lfl/fW=1
．． 583P If31/fw・1.085 Furthermore, the condition values for conditions (V) to (vii) that are desirable to satisfy are: d□zw/f2=0.858, dz3w/fw=0.
809. S1N-S1p=18.5.

FIG. 3 shows the lens arrangement at the wide-angle end of this second embodiment.

An aberration diagram for Example 1 is shown in FIG. 4, and an aberration diagram for Example 2 is shown in FIG. 5.

4 and 5, (A) shows the aberration situation at the wide-angle end, (B) shows the intermediate focal length, and (C) shows the aberration situation at the telephoto end.

dsA and gSA represent spherical aberrations for the d-line and g-line, respectively, SC represents the sine condition, and S and M represent the sagittal and meridional image surfaces for the d-line, respectively.

In each example, aberrations are well corrected.

Next, two embodiments of the compact zoom lens according to claim 2 will be described. The lens configurations of these two examples are as shown in FIGS. 6 and 7.

Example 3 f: 36-102 １　　　　rl 1 -63P099 2 21.488 3 22.869 4 3112.066 5 21.745 6 ~ 36.401 7 -69.828 8 Q) (Aperture) 9 17.744 10 71.805 11 -41.227 12 15.442 13 30.802 14 -21.612 15 -46.434 16 -17.977 17 -17.620 , FN0=3P23~7.9 ,ω=61.5~23P7 d.

1,400 1,140 4,590 Variable 3,520 0,700 0,900 0,800 2,080 0.810 3,700 2,400 2,560 Variable 3,029 2,538 2,233 n, ν4 1.75500 52.3 1.64769 33P8 3 1.71300 53P9 4 1.84688 23P8 1.56384 60.8 1.83400 37.3 1.56384 60.8 1.51680 64.2 1.75500 52.3 18 41.394 5.598 101.69
895 30.019 -41.474 2.8
3320 -20.621 1.748 111
．． 69680 55.021 -71.549 Variable amount f 36 60.597 102d
412.644 8.572 1.631d1
411.438 4.127 1.704 Condition value f31/1fl=0.536, 1f11/fw4.5
83P1f31/fw=0.848 Furthermore, the condition values for conditions (V) to (vii) that are desirable to satisfy are a12W/T2=o, gs7. dz3w/fw:0.8
65. ν1N−ν, P=18.5.

FIG. 6 shows the lens arrangement at the wide-angle end of Example 3.

Example 4 f236~102, FNO"3P23~7.91
, ω=61.7~23P7□ r , d , j
nj νJ1 -63P501 1.4
00 1 1.75500 52.321.952 23P546 4362.477 21.613 -36.888 69.139 CxI (aperture) 17.576 70.297 40,979 15,260 31,032 -21.541 50,059 18,012 18,504 51,579 48.629 19,945 73,626 1.140 4,590 Variable 3,520 0,700 0,900 0.800 2.080 0,810 3,700 2,400 2 , 560 variable 3, 645 2, 553 2, 429 5, 212 3, 235 1, 324 1.64769 1.71300 1.84666 1.56384 1.83400 1.56384 1.51680 1.80420 1.76182 1. 64000 33P8 53P9 23P8 60.8 37.3 60.8 64.2 46.5 26.6 60.2 Variable amount f 36 60.597 102d
412.810 8.737 1.797d1
410.610 3P299 0.877 Condition value f3t/1f11”o, 536, 1f11/fw・1
, 583P1f31/fw=0.848 Furthermore, the condition values for conditions (v) to (vii) that are desirable to satisfy are d12W/f2=0.857. d23W/fW: 0.8
65. ν0,−shi, ,=18.5.

FIG. 7 shows the lens arrangement of the embodiment at the wide-angle end.

An aberration diagram for Example 3 is shown in FIG. 8, and an aberration diagram for Example 4 is shown in FIG. 9.

In Figures 8 and 9, (A) shows the aberration situation at the wide-angle end, (B) shows the intermediate focal length, and (C) shows the aberration situation at the telephoto end.
dsA and gsA represent spherical aberrations for the d-line and 9g-line, SC represents the sine condition, and S and M represent the sagittal and meridional image surfaces of the d-line, respectively.

As shown in FIGS. 4.5, 7, and 8, aberrations are well corrected in each example.

[Effects of the Invention] As described above, according to the present invention, a novel compact zoom lens can be provided. As mentioned above, this zoom lens has the chromatic aberration of magnification corrected in the third group, so it is possible to suppress fluctuations in the chromatic aberration of magnification of the entire system due to zooming.
Performance is good.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the group device and group movement during zooming in the small zoom lens of the present invention, and FIGS. 4 and 5 are aberration diagrams related to Example 1.2, and FIGS. 6 and 7 are lens grooves related to Example 3P4 regarding the zoom lens of claim 2. The bottom view, Figures 8 and 9 are for the above embodiments 3 and 4.
FIG. Figure ■ ■ ■ 俤 A Figure (C) (Actual sales example t Va) 178- , (= fl, 4' / Shishi Onanomu comatic aberration Fj, 2J Masahirojo Sumi (Sc) j1, 8' 3/, 6' 5000 500 1-track aberration ζri) F5, 1 Correct Daijoko (SC) 19B' ] Photo 5 Figure (F3 N Kabutage/IZIll) Darkness, 6, Distance) 19.8" -5, 000500 Distortion R (〆) F'1.7 14.'3'' It surface A'Z difference (UA) Correct husband condition (SC) Astigmatism 1 Figure 5 (C) [Extreme example 2. f injury) 119' Plan Ifl aberration r%) (Negative F, JG /F3P1' sine 14 cases (SC n ε Figure (I3) = Cell I voice 13 Chudan Jiao, Tun, Distance 1th) 194゛ Distortion number Base (-A) F'7.9 Seishikime* (SC) 8 Figure (C) Sales example 3 wish arrest 4) 778゛ Distorted difference (惺) F3P2.3 True Gojo Sen F (SC) 3θ9゛Figure 19 (A) = = Force 9 + 14° Non: angle ☆ 1 soldier) jO9° - 50005, ○O Distortion aAnu * (xnF 5.4G Correct name condition (5C) 19, 4° Diagram (B) J9.4° Distortion Curved Sword (2) 791 H, f3' -0500050 Spherical Aberration (SA) Positive Tegenyui (5Cn-0500050 Astigmatism, Aberration 6 9 Figure (ko) Example 4 Pu S! Haton 776゛Distortion a sword nu 21%)

Claims (1)

[Claims] 1. First to third groups are arranged sequentially from the object side to the image side, the first group has a negative focal length f_1, and the second group has a positive focal length. The third group has a negative focal length f_3, and the first to third groups move toward the object side while changing the distance between them, so that magnification is changed from the wide-angle side to the telephoto side. , The above third group has 3 positive, negative, and positive groups from the object side to the image side.
When the lenses are arranged in this order and the second lens is a negative lens and the third lens is a positive lens, and the focal length of the entire system at the wide-angle end is f_W, The above f_1, f_2, f_3 and f_W are (i) 0.3
<|f_3|/|f_1|<1.0(ii)1.2<|
f_1|/f_W<2.3(iii)0.9<|f_3
If the condition |/f_W<1.4 is satisfied, the Abbe number of the second negative lens in the third group is ν_3_N, and the Abbe number of the third positive lens is ν_3_P. When these ν_3
A small zoom lens characterized in that _N and ν_3_P satisfy the following condition: (iv) ν_3_N>ν_3_P. 2. The first to third groups are arranged sequentially from the object side to the image side, the first group has a negative focal length f_1, the second group has a positive focal length f_2, The third group has a negative focal length f_3, and as the first to third groups move toward the object side while changing the distance between them, magnification is changed from the wide-angle side to the telephoto side. Four lenses, positive, negative, positive, and negative, are arranged in this order from the object side to the image side, and the second lens, the negative lens, and the third lens, the positive lens, are cemented together. , when the focal length of the entire system at the wide-angle end is f_W, the above f_1, f_2, f_3 and f_W are (
i) 0.3<|f_3|/|f_1|<1.0(ii)
1.2<|f_1|/f_W<2.3(iii)0.9
<|f_3|/f_W<1.4, the Abbe number of the second negative lens in the third group is ν_3_N, and the Abbe number of the third positive lens is ν_3_N. When the number is ν_3_P, these ν_3
A small zoom lens characterized in that _N and ν_3_P satisfy the following condition: (iv) ν_3_N>ν_3_P.