JPH04146407A - High variable power zoom lens - Google Patents

Abstract

PURPOSE:To offer a zoom lens having a high variable power and further, the compact entire length by providing six lens groups and moving them so as to change the intervals of respective groups at the time of power variation. CONSTITUTION:The zoom lens is composed of a first lens group (I) having the positive refractive power, a second lens group (II) having the negative refractive power, a third lens group (III) having the positive refractive power, a fourth lens group (IV) having the negative refractive power, a fifth lens group (V) having the positive refractive power, and a six lens group (VI) having the negative refractive power in order from the object. Varying power is carried out by changing the intervals of respective lens groups. By this constitution, the high variable power can be obtained, and further, a moving quantity at the time of zooming is reduced, so that the zoom lens having a compact entire length is realized.

Description

[Detailed Description of the Invention] The present invention relates to a high variable magnification zoom lens,
In particular, the present invention relates to a high-power zoom lens that can be used as an interchangeable lens for an eye reflex camera or the like.

Shikama five techniques! In recent years, the market for interchangeable lenses for reflex cameras has been dominated by zoom lenses, and the gap in demand between them and single-focal-length lenses is widening. And the zoom lens is also a so-called standard zoom lens (for example, the focal length is 35 ~
The market needs have increased from 80mm, etc.) to zoom lenses that cover wide-angle to telephoto lenses and have high zoom ratios.

Various optical systems have been proposed in the past that cover the range from wide-angle to telephoto and have a high zoom ratio (for example, Japanese Patent Laid-Open No. 57-2014, Japanese Patent Application Laid-Open No. 57-164709,
No. 57-164710, No. 59-195214, No. 60-39613, No. 63-205629, No. 63
-266414, 64-10207, 63-2
No. 66415, No. 61-258219, JP-A-1-1
91819 etc.).

However, these zoom lenses had a five-group structure, and the length of the entire system was too large to achieve a high zoom ratio, making it difficult to call it compact.

Therefore, an object of the present invention is to provide a zoom lens having a large zoom ratio and a compact overall length.

In order to achieve the above object, the zoom lens of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a second lens group having a positive refractive power. 3 lens group, 4th lens group with negative refractive power, 5th lens group with positive refractive power, and 6th lens group with negative refractive power.
It consists of lens groups, and is characterized in that the magnification is changed by changing the distance between each of the lens groups.

In this way, six lens groups are provided, and the distance between each lens group changes during zooming, so the amount of movement of the entire lens system from the wide-angle end to the telephoto end is less than that of the conventional example. Compared to the case of such a five-group configuration, the number of units required is relatively small.

Among them, the distance between the first lens group and the second lens group, the third
The distance between the lens group and the fourth lens group and the distance between the fifth lens group and the sixth lens group are respectively increased, and the distance between the second lens group and the third lens group and the distance between the fourth lens group and the fifth lens group are increased. It is preferable that the zooming is performed from the wide-angle end to the telephoto end by moving each of the lens groups so as to decrease the distance between the two lens groups.

When changing the magnification from the wide-angle end to the telephoto end, the first lens group and the second
By moving the first lens group and the second lens group so that the distance between them becomes larger, the second lens group can have a large power changing effect.

Furthermore, when zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the third lens group is made smaller. 1st・
By moving the 2nd and 3rd lens groups in this way, it is possible to achieve a variable power ratio of approximately 10x from the wide-angle end to the telephoto end.

Furthermore, when changing the magnification from the wide-angle end to the telephoto end, by moving the third and fourth lens groups so that the distance between them becomes larger, the floating effect In particular, spherical aberration is well corrected.

Similarly, when changing the magnification from the wide-angle end to the telephoto end, the distance between the fourth lens group and the fifth lens group becomes smaller, and the distance between the fifth lens group and the sixth lens group becomes larger. By moving the lens group, the fifth lens group, and the sixth lens group, the curvature of field can be favorably corrected due to the floating effect.

As described above, when changing the magnification from the wide-angle end to the telephoto end, by moving each lens group so that the distance in front of each lens group becomes larger, a wide range of focal lengths can be covered from wide-angle to telephoto. Shitsuru, large variable magnification ratio (about 10x)
, and a zoom lens with good performance over the entire range can be realized.

Further, when changing the magnification from the wide-angle end to the telephoto end, by moving the lens groups other than the second lens group toward the object side, the total length of the lens at the wide-angle end can be suppressed to a compact size.

In order to achieve a zoom lens that has higher optical performance while achieving a higher zoom ratio and a more compact overall length, it is desirable to have a configuration that satisfies the following conditional expressions (1) to (2).

0.2<f+/fv<0.5...
...■0, 07< f3/ fT<0.15
・・・・・・■-50< (f+23)w
+ (fass) II (f, 23) vX (f4sa
)u/f-<0......■Here, fI = Focal length of the first lens group f3: Focal length of the third lens group fT: Focal length of the entire system at the telephoto end fII: At the wide-angle end Focal length of the entire system (f+23)w
``The first lens group, the second lens group, and the third lens group at the wide-angle end
Composite focal length (fass) of lens group: Composite focal length of the fourth lens group, fifth lens group, and sixth lens group at the wide-angle end.

In the conditional expression, if f+/fT exceeds the upper limit, the first
If the refractive power of the lens group becomes too weak, the amount of movement of the first lens group at the telephoto end becomes large, which goes against compact design and makes it difficult to accurately position the first lens group mechanically. Also, if f1/fv exceeds the lower limit, the first
If the refractive power of the lens group becomes too strong, the off-axis illuminance at the wide-angle end will drop significantly, and in order to secure the illuminance, it is necessary to increase the lens diameter of the first lens group, which goes against the trend of compact design. become. Furthermore, off-axis flare components are introduced, resulting in deterioration of off-axis MTF performance.

In conditional expression ■, if fs/f- exceeds the upper limit, the third
If the refractive power of the lens group becomes too weak, the distance between the second and third lens groups must be increased in order to obtain the variable power ratio at the wide-angle end, and the total length of the lens at the wide-angle end increases. At the same time, the illuminance outside the axis becomes insufficient. Furthermore, if h/fr exceeds the lower limit value and the refractive power of the third lens group becomes too strong, the amount of movement of the third lens group will become smaller when changing the magnification from the wide-angle end to the telephoto end, and the refractive power of the third lens group will become smaller. Although this contributes to compactness, it becomes difficult to properly correct spherical aberration.

Conditional expression (2) defines the distance between the third lens group and the fourth lens group at the wide-angle end in order to shorten the overall lens length. If the upper limit of conditional expression ■ is exceeded,
The overall length of the lens increases at the wide-angle end, making it impossible to achieve compactness. Furthermore, if the lower limit is exceeded, the third lens group and the fourth lens group interfere at the wide-angle end, making it physically impossible to configure.

According to the present invention, by satisfying the following conditional expression, a compact zoom lens with better performance can be realized.

0, 2< f2/ful < 0.9
...■ However, f2: focal length of the second lens group.

In conditional expression (■), if l h/f,l exceeds the upper limit value, in order to secure the focal length at the wide-angle end, the second and third
It is necessary to further widen the distance between the lens groups, which increases the overall length and makes it difficult to secure the illuminance ratio. Furthermore, if f2/fi+ exceeds the lower limit value, although it contributes to shortening the overall length at the wide-angle end, the amount of movement of the first group increases to ensure the focal length at the telephoto end, so the lens barrel configuration The above problem occurs. Furthermore, since the negative power of the second lens group becomes too strong, it becomes difficult to correct spherical aberration, especially at the telephoto end.

In this way, from the definition of the power of the second lens group in conditional expression (2), it is also possible to determine the condition for the distance between the 2° and the third lens group expressed by the following conditional expression.

10< (Tz, t)II/ (T2.3)T<50
・・・・・・■Here, (72,3)11
: Distance between the second lens group and third lens group at the wide-angle end (T2.3) T: Distance between the second lens group and the third lens group at the telephoto end.

When (72,3)i+/(T13)T exceeds the upper limit in conditional expression (2), the total length at the wide-angle end increases, and in addition, it becomes difficult to ensure the illuminance ratio. (Ta,s)l,/(
72,8) When T exceeds the lower limit, it is necessary to increase the power of the second group beyond the range of conditional expression (■) in order to secure the focal length at the wide-angle end, resulting in spherical aberration at the telephoto end. It becomes difficult to correct.

In order to achieve a zoom lens with higher magnification and higher performance than in the past, many lenses have a configuration of five lens groups. In the present invention, by adding the sixth lens group having negative refractive power, the amount of movement of the variator is reduced, making it easier to configure the lens barrel, and the fifth lens group is added during zooming. Aberrations are well corrected by changing the interval between the sixth lens groups.

At this time, it is desirable to satisfy the following conditional expression.

0,01<(Ta,s)i+/(T6.8)T<0
．． 5 ・・・・・・■Here, (Ts, e)u:
Distance between the fifth lens group and the sixth lens group at the wide-angle end (Ts, a)y: Distance between the fifth lens group and the sixth lens group at the telephoto end.

In conditional expression (0), if (Ts, a)i/(T5.6)T exceeds the upper limit, the total length will increase at the wide-angle end, which is against compactness. Also, from the wide-angle end to the telephoto end, the 5th. The floating effect of the sixth lens group becomes smaller, making it difficult to satisfactorily correct aberrations over the entire range. When (Ts, e)i+/(Ts,s)v exceeds the lower limit value, it becomes difficult to correct field curvature near the telephoto end.
Furthermore, in order to obtain a desired magnification ratio, the amount of movement of each group becomes large.

Male J [Example] Hereinafter, an example of a high variable power zoom lens according to the present invention will be shown.

However, in each example, rt (x=1.2.3.
, , , ) is the radius of curvature of the i-th surface counting from the object side, d, (i=1.2°3,,,,) is the distance on the i-th axis counting from the object side, and N: (14Jw3+01
．． )*ν+ (i=1.2.3. , , , ) is the refractive index for the d-line of the i-th lens counting from the object side.

Indicates the Atsube number. Further, f indicates the focal length of the entire system, and FNo indicates the open F number.

In the examples, a surface with a radius of curvature marked with * indicates that it is an aspherical surface, and is defined by the following equation representing the shape of the aspherical surface.

2, where, be.

Focal length f+, fz, fa, fa, fs of each lens group, etc.
, fa, (f123)11 and (fasa)v are also shown.

<Example 1> f = 28.8~100.0~290°OF No.
= 4.6~5.9~5.81"IL 凰-juJC"l
LL! 1 engineering Pego r+ 167.6J3 d, 2.800 Ns 1.84866 ν+
23.82r41~212.318 Σd=129.908~150.688~154.38
1 valve” [grandson 1 rss: ε=O, 100OOX 10A, =
-0,97183X 1O-7 Aa=-0,18452X 10-' As=-0.18756X 10-' A+ s:0.42606
,28124X 10-13 focus 1j1 curtain = L "87.01.
5.72. f4”-30,19°fs:44.14
．． fa” 103.5° (f+23h=13.
46. (fn5a) w=-53,47 <Example 2> f ~28.8~100°0~290.0 F N,
~4.64~5.80~5.8349.945 5,50O 1,77250 ν3 49.77 1,20O N141. '/'/Z51J ν144υ, ll 91.290 Σd= 130.107~149.894~154.2
88 directions'' 11 蓬1 r37: ε=0.10000X 10 A4=0.44058X 1O-8 As knee 0.13285X10-' As=0.24173x 1O-8 A+5=-0,22639X10 1 AIz; 0.74894X 10-”KunJj1茄-f+=85.42.fa mini-1,19,h”26
．． 41. ram-30,56゜ram50.75.
fe=-175,00°(f+23)l, z13.
24. (f4sg)4I=-58,25〈Example 3
〉 f=28.8~100.0~260. OFno=4.6
4-6.2-6゜m1" Soba] UJC Town" Prince Rei L
L ball 1r+ 239.549 d+ 2.800 N+ 1.84866 Shi 1 23.82 r3 100.993 ds 8.000 N2 1.49310 83.58 53.224 185.451 107.357 5.343 N3 1.80500 ν30.4
00~37.177~55.9550.840 Na
1.85000 ν440.97 40.04 -79.076 r++ -30,043 ds 3JOONs 1.80750 ν,
35.43dos 1.200 Ne 1.77
250 Va 49.77r+2 33.422 d+2 5,00O 1,75000 Schiff 25.14 37.391 3.70O Nt*1.51680 Sil964.20 r3a -20,879 sa 1.400 N211.84666 ν21I2
3.83r3s 123.032 SS 1.000~13.930~17.110rss-18
3,876 SS 3.500 Na+1.51680 Si2t64
．． 20rss*-29,459 d3m 1.500 Na21.83400ν2□
37.05 ram 31.158 d4s 3.50ON231.67339 shi2
329.25r4+-212.318 Σd=126.661~161.020~177.34
2 valve lit grandson 1 ram: s; 0.100OOX 10A4 knee 0.11056X 10-'As; 0.20644X 10-@ As"0.35397X 10-" Au+=0.19751X 10-" A+2= 0.18207X10 -” Jiao Ju1 Eggplant 2 f+=98.60. f2”-16,42,fa”2
5.05. f4=-30,21°fs”78.37
．． ram-250,0°(f+23)u=12.0
4. (f4st)w=-38,62 Next, f+/ry in the conditional expression (■) in Examples 1 to 3 above, and the conditional expression (■)
b/ft in and (f+2s)II+(f
Table 1 shows the values of as6)&l(f+2a)wX(Lsa)w/f-.

In addition, I fa in conditional expression (2) in Examples 1 to 3 above
/ful, (T2.3)+7/ (T
a, a) r and (Ts, a:) +/ (T
a, 6) The values of T are shown in Table 2.

Table 1 Table 2 Figures 1 to 3 are lens configuration diagrams corresponding to Examples 1 to 3, respectively, with arrows (ll), (m2
), (m3), (m=), (m5) and (m6)
are the wide-angle end (W) of the first group (1), second group (■), third group (■), fourth group (■), fifth group (V), and sixth group (VI).
) to the telephoto end (T).

In Example 1, the first lens group (I) to the sixth lens group (V
All the lens groups up to I) are moved independently, and in Example 2, the third lens group (III), the fifth lens group (V), the fourth lens group (IV), and the sixth lens group ( Vl)
are moved as one unit. In Embodiment 3, the first lens group (I) to the fifth lens group (V) are moved independently, and the sixth lens group (V) is fixed to perform zooming.

Note that a diaphragm (A) is provided behind the lens closest to the object in the third group (III).

In Example 1, the positive first group (I
) consists of a negative meniscus lens that is concave on the image side, a positive biconvex lens, and a positive meniscus lens that is convex on the object side, and the negative second group (n) is a negative meniscus lens that is concave on the image side.
It consists of a positive meniscus lens that is convex on the image side, a negative biconcave lens, a positive lens that is biconvex, and a negative WJ concave lens. A concave negative meniscus lens and a biconvex positive lens.

It consists of a negative meniscus lens that is concave on the image side and a positive biconvex lens.The negative fourth group (TV) consists of a negative meniscus lens that is biconcave, a positive lens that is biconvex, and a negative lens that is biconcave. The fifth group (V) consists of two biconvex positive lenses and a negative meniscus lens concave on the object side, and the negative sixth group (VI
) consists of a positive meniscus lens convex to the image side, a negative biconcave lens, and a positive biconvex lens.

Note that the object-side surface of the second lens in the sixth group (VI) is an aspherical surface.

In Example 2, the positive first group (I
) consists of a negative meniscus lens that is concave on the image side, a positive biconvex lens, and a positive meniscus lens that is convex on the object side, and the negative second group (n) is a negative meniscus lens that is concave on the image side.
Consisting of a WJ concave negative lens, a biconvex positive lens, and a biconcave negative lens, the positive third group (III) is a positive meniscus lens convex on the object side, an aperture stop, and a negative meniscus lens concave on the image side.

It consists of a biconvex positive lens, a negative meniscus lens concave on the image side, and a biconvex positive lens, and the negative fourth group (IV) consists of a biconcave negative lens, a biconvex positive lens, and a biconcave negative lens. The positive fifth group (V) consists of two biconvex positive lenses and two biconcave negative lenses, and the negative sixth group (VI) consists of a positive meniscus lens convex to the image side and a biconcave negative lens. It consists of a concave negative lens and a biconvex positive lens.

Note that the object-side surface of the second lens in the sixth group (VI) is an aspherical surface.

In Example 3, in order from the object side, the positive first group consists of a negative meniscus lens concave on the image side, a biconvex positive lens, and a positive meniscus lens convex on the object side. The second group (n) is a negative meniscus lens concave on the image side;
It consists of a positive meniscus lens that is convex on the image side, a negative biconcave lens, a positive lens that is biconvex, and a negative lens that is biconcave. Concave negative meniscus lens, biconvex positive lens.

It consists of a negative meniscus lens that is concave on the image side and a positive biconvex lens.The negative fourth group (IV) consists of a negative biconcave lens, a positive VI convex lens, and a negative biconcave lens. The fifth group (V) consists of two biconvex positive lenses and two biconcave negative lenses, and the negative sixth group (VI) consists of a positive meniscus lens convex to the image side, a biconcave negative lens, and a biconcave negative lens. It consists of a convex positive lens.

Note that the object-side surface of the second lens in the sixth group (VI) is an aspherical surface.

4 to 6 are aberration diagrams corresponding to Examples 1 to 3, respectively, in which (W) indicates the focal length at the wide-angle end,
(M) shows the aberration at the intermediate (middle) focal length Ill, and (T) shows the aberration at the focal length at the telephoto end.

In addition, the solid line (d) represents the aberration for the d-line, and the broken line (
SC) represents the sine condition. Furthermore, the dashed line (DI) and the solid line (
DS) represents astigmatism on the meridional plane and the sagittal plane, respectively.

As explained above, according to the present invention, in order from the object side, the first lens group has a positive refractive power, the second lens group has a negative refractive power, and the second lens group has a positive refractive power. 3 lens groups, a 4th lens group with negative refractive power, a 5th lens group with positive refractive power, and a 6th lens group with negative refractive power.
It consists of lens groups and is configured to change the magnification by changing the distance between each of the lens groups, so it is possible to obtain a large zoom ratio and to reduce the amount of movement during zooming. This makes it possible to realize a zoom lens with a compact overall length.

In particular, when changing the magnification from the wide-angle end to the telephoto end, if the lens groups other than the second lens group are moved toward the object side, the overall length at the wide-angle end can be made compact.

Further, if the configuration satisfies the above conditional expressions (1) to (2), it is possible to achieve a zoom lens that has higher optical performance while increasing the zoom ratio and making the overall length more compact.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are lens configuration diagrams corresponding to Examples 1 to 3 of the present invention, respectively. FIG. 4, FIG. 5, and FIG. 6 are aberration diagrams corresponding to Examples 1 to 3 of the present invention, respectively. Applicant Minolta Camera Co., Ltd.

Claims (1)

[Claims] (1) In order from the object side: a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a negative refractive power. A fourth lens group with power,
A zoom lens comprising a fifth lens group having a positive refractive power and a sixth lens group having a negative refractive power, the zoom lens being variable in power by changing the distance between each of the lens groups. (2) The zoom lens according to claim 1, wherein lens groups other than the second lens group are moved toward the object side during zooming from the wide-angle end to the telephoto end. (3) When changing magnification from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group, the distance between the third lens group and the fourth lens group, and the distance between the fifth and sixth lens groups The lens groups are moved so as to increase the distance between the two lens groups, respectively, and to decrease the distance between the second lens group and the third lens group, and the distance between the fourth lens group and the fifth lens group. A zoom lens according to claim 1. (4) The zoom lens according to claim 3, which satisfies the following conditions: 0.2<f_1/f_T<0.5 0.07<f_3/f_T<0.15 -50< (f_1_2_3)_w+(f_4_5_6)
＿w−(f_1_2_3)_w×(f_4_5_6)_
w/f_w<0 where, f_1: Focal length of the first lens group f_3: Focal length of the third lens group f_T: Focal length of the entire system at the telephoto end f_w: Focal length of the entire system at the wide-angle end (f_1_2_3)_w : Combined focal length of the 1st lens group, 2nd lens group, and 3rd lens group at the wide-angle end (f_4_5_6)_w: Combined focal length of the 4th lens group, 5th lens group, and 6th lens group at the wide-angle end .