JPS6055313A - Zoom lens - Google Patents

Abstract

PURPOSE:To shorten the overall length of a zoom lens for a single-lens reflex camera which has an about 4 F number and an about 3X zoom ratio from a wide angle to an intermediate telephoto range while reducing the movement extents of respective lens groups including a lens group to which the diaphragm of the zoom lens is attached. CONSTITUTION:The lens system consists of the 1st, the 2nd, the 3rd, and the 4th lens groups successively from an object side, and those four groups are all moved to vary the power. Said 1st lens group consists of the 1st positive lens, a negative meniscus lens having a convex surface on the object side, the 3rd negative lens, and the 4th positive lens cemented to the 3rd lens successively from the object side, and has negative refracting power on the whole. The 2nd lens group consists of the 4th positive lens, the 6th positive lens, and the 7th negative lens cemented to the 6th lens, and has positive refracting power on the whole. The 3rd lens group consists of the 8th positive lens, the 9th negative lens cemented to the 8th lens, and the 10th negative lens, and has negative refracting power on the whole. Further, the 4th lens group consists of the 11th positive lens, the 12th negative lens cemented to the 11th lens, and the 13th positive lens, and has positive refracting power on the whole. Then, the respective lenses satisfy inequalities.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens for a single-lens reflex camera having an F number of about 4 and a zoom ratio of about 3 times from wide angle to medium telephoto.

Regarding zoom lenses with specifications such as those mentioned above, so-called two-group type zoom lenses have been known that change the magnification by changing the mutual spacing between a front group with negative refractive power and a rear group with positive refractive power. There is.

However, when trying to achieve a two-group type with a zoom ratio of about 3x as described above, the amount of movement due to zooming of the rear group becomes too large, and the aperture that moves along with the rear group becomes too large. On the other hand, in order to maintain the precision of the automatic aperture mechanism at a high level, a complicated mechanism is required, resulting in drawbacks such as an increase in the size of the mechanical system, or when attempting to reduce the amount of movement of the rear group. The total length of the lens increases on the focal point side, and it becomes necessary to increase the lens diameter to secure the necessary amount of peripheral light, or to strengthen the refractive power of each lens group to reduce the total lens length, which reduces various aberrations. Does it increase the number of lenses or increase the number of lenses to correct aberrations? If you are forced to do so, you will have a number of disadvantages.

The present invention has focused on this point, and aims to provide a high-power zoom lens with excellent performance, in which the moving claws of each lens group including the lens group accompanied by the diaphragm are small, and the overall length is short.

First, the configuration of the present invention will be described. In order from the object side, there are a positive lens, a second lens, a negative meniscus threader with a convex surface facing the object side, a negative third lens, and the third lens. and a fourth lens which is a positive lens laminated together, and has a negative refractive power as a whole; a fifth lens which is a positive lens, and a sixth lens which is a positive lens;
a first lens group consisting of a seventh lens which is a negative lens bonded to the sixth lens and which exerts a positive bending force as a whole; an eighth lens which is a positive lens; and the eighth lens A 10th lens group consisting of a 9th lens, which is a negative lens, and a 10th lens, which is a negative lens, and which has negative refractive power as a whole, = a 1st lens that is a positive lens, and the 10th lens that is a positive lens; and a first lens group consisting of a twelfth lens, which is a negative lens, and a thirteenth lens, which is a positive lens, which are laminated together and have a positive refractive power as a whole, and all of the four groups are movable. This is an optical system that changes magnification according to the following, and is characterized by satisfying the following conditions.

(1) 1.1<l f r l/ f w<1.7
, f I<0' (2) 0.8<f■/f to ψ<1
．． 2(3)1.1<l fml/fw<1.7, f+
u<0(4) 1.8< f rv / f w <2
．． 4 (5) 8< f + / f w <50 (6)
n 4n 3 ) 0.2 (7) n B n 9 > 0.15 (8) nl 2 rz 1 > 0.2 (9) 0.4
5<l rl 9 l/fw<0.6, rl9<Of
l: Composite focal length of the first lens group f■: Composite focal length of the ■th lens group fm: Composite focal length of the ■th lens group f9: Composite focal length of the ■th lens group fw: Shortest hot spot distance of the entire system fl: Focal length history of the lens nl: Refractive index of the glass material used for the i-th lens r1. : The radius of curvature of the bonding surface of the first lens and the twelfth lens In the present invention configured in this way, based on the so-called two-group type, the rear group is further provided with three lens groups in order from the object side.
That is, the lens is divided into four lens groups as a whole, and the magnification is changed by changing all the intervals between the four lens groups. With this configuration, the degree of whiteness increases in the movement of each lens group during zooming, the Merino 1~ increases in aberration correction, and the movement of each lens group via the diaphragm group is controlled by a small claw. It becomes possible to l-roll.

Next, each of the above conditions will be explained.

Condition (1) relates to the refractive curve of the first lens 4. If the lower limit of condition (1) is exceeded, the refractive power of the first lens 112 becomes too strong, causing overcorrected spherical aberration and astigmatism, making it difficult to maintain good optical performance. Furthermore, if the upper limit of condition (1) is exceeded, the refractive power of the lens group weakens, and - the back focus necessary for an eye reflex camera lens cannot be secured, or the total length of the lens becomes long to secure the back focus. This brings about a drawback.

Conditions (2), (3) and (4) are respectively No.
Regarding the refractive power of the lens group (2), this is a necessary condition to jointly suppress the number of lenses constituting the lens to the minimum necessary amount and to suppress the movement (2) of each lens group to a small value.

If the lower limits of conditions (2), (3), and ('l) are exceeded, the refractive powers of the 1st, 2nd, and 1st V lens groups will become too strong, and various aberrations will increase, or This is undesirable since the lens structure becomes complicated in order to correct the generated aberration. Also, conditions (2) and (3).

If the upper limits of (4) are exceeded, the refractive powers of the 1st, 2nd, and 1st V lens groups will become too weak, and the amount of movement will become too large, causing the above-mentioned problems, or increasing the total lens length. This has the disadvantage of leading to

In the case of the present invention, by satisfying conditions (2), (3), and (4), the lens configuration of the 1st, 2nd, and tV lens groups can be reduced to 3 lenses each, and the required amount of 5N/ It is now possible to configure the number of sheets within the JX limit.

Condition (5) relates to the refractive power of the first lun. The lens is a positive lens with weak refractive power, and is particularly effective at correcting distortion on the short focal length side. Do J. Condition (5)
When the lower limit of is exceeded, the eyebrow 1 analysis power of the first rune becomes 1 ±
Correction of distortion aberration; (although it is more effective, it causes chromatic aberration of magnification for the 16-ray bundle number 3, which should be imaged at the periphery of the screen, which is not desirable). Moreover, if the upper limit of item (4-(5)) is exceeded, the refractive power of the first lunion +t 51i becomes too large, and the effect of the second lunion becomes weak, and the distortion cannot be corrected.

Condition (6) relates to the refractive index of the glass materials used for the third and fourth lenses. The third lens and the fourth lens are laminated in the first lens group, and the effect of the laminated surface mainly contributes to correction of spherical aberration and dichromatic aberration. If condition (6) is violated, the convergence effect on the bonded surfaces will be weakened, and overcorrected spherical aberration will remain in the entire lens group. In order to maintain good chromatic aberration, condition (6) must be satisfied, and the Abbe numbers of the glass materials used for the third and fourth lenses should be set to ν3. When set to v4, ya3-乍4>
It is desirable to satisfy 20.

Condition (7) relates to the refractive index of the glass material used for the eighth lens and the ninth lens. The eighth lens and the ninth lens are laminated together and used in the first lens group, and the effect of their mating surfaces mainly contributes to correction of spherical aberration and axial chromatic aberration. If condition (7) is violated, the convergence effect on the bonded surfaces will be weakened, and overcorrected spherical aberration and axial chromatic aberration will remain. In addition, in order to highly correct axial chromatic aberration, the condition (
7), and when the Atsube numbers of the glass materials used for the 8th lens and the 9th lens are each '1'8 + ν9, then Y. It is desirable to satisfy -νo>20.

Condition (8) relates to the refractive index of the glass material used for the first lens and the twelfth lens. The first lens and the twelfth lens are used in a bonded state within the first lens group, and the effect of the bonded surface mainly contributes to correction of spherical aberration and lateral chromatic aberration.

If condition (8) is violated, the divergence effect on the bonded surfaces will be weakened, and undercorrected spherical aberration and chromatic aberration of magnification will remain, which is not preferable. In addition, in order to correct lateral chromatic aberration to a higher degree, condition (8) should be satisfied, and the Atsbe number of the glass materials used for the first lens and the twelfth lens should be increased to 1. When ν12, it is desirable that 12-'I'll>to be satisfied.

Condition (9) relates to the radius of curvature of the bonding surfaces of the first lens and the twelfth lens. This condition (9), together with condition (8), contributes to correction of spherical aberration, dichromatic aberration, and distortion aberration. If the lower limit of condition (9) is exceeded, the radius of curvature of the bonded surface becomes small, the divergence effect increases too much, and overcorrected spherical aberration occurs, which is not preferable. On the other hand, when the upper limit of condition (9) is exceeded, the radius of curvature of the bonded surfaces becomes large, the divergence effect weakens, chromatic aberrations, especially lateral chromatic aberrations remain large, and the effect of correcting distortion aberrations decreases to 1. However, barrel-shaped distortion remains, particularly on the short focal length side, which is undesirable.

Examples of the present invention will be described below. , where r is the radius of curvature of each lens surface, d is the lens thickness or lens spacing, n is the refractive index of each lens, and ν is the Abbe number of each lens.

[Example 1] FNO1: '4 f = 28.8 ~ 8
2. Or, d n l 375.000 3.24 1.67790 . 5
5.32 -1670.668 0.10 3 t37. ci77 1.95 1.8g300 4
0.84 31.873 7.39 5 -975.783' 1.94 1.487/19
70.16 26.650 5.89 1.8051
8 25. /17 48.983 Variable 8 51.024 4.70],,67'790'
55.39 -t2a, s47 o, t.

10 37.727 6.98 1.72916 54
．． 711 31.514 1.77 1.80518
25.412 520';000 Variable 13 -52.842 3.55 1.75520 2
7.514 -22.119 1.40 1.5182
1 65.015 57.456 0.78 16 -348.158 1.22 1.79952
42.217 99.879 Variable 18 173.534 7,42 1.56873 6
3.219 -14.155 1.49 1.83/1
00 37.220, -33.334 0.10 21 -198.800 2.13 1.83400
37.222 -75.500 1 f I I =40.27=1.398・fwf
n=29.61=1.028・f wl f m l
=42.76=1.485・fwf, =60.54
=2.102・fwf 1=452.05=15.70
・fwn 4 − n 3 =0.318 n B −n g =0.237 n12 ni □ = 0.265 1 r 1! ] l =14.155=0.491・f
w [Example 21 FMO1: 4 f = 28.8
~g2. Or d n l 354.171 3.31 1.69100 5'
1.82 = -1766,390,10 :J, 148.147 1.97 1.83481
42.74 31.834 7.47 5 -607.300 1.94 1.48749 7
0.16 26.515 5.93 1.78472
25.77 50.157 Variable 8 53.467 4.05 1.62041. 60
．． 39 -97.436 0. ], 0 10 34.177 6.99 1.72916 54
．． 711 -33.472 1.77 1.8υ51g
25.412 240.699 Variable 13 -54.206 2.4o 1.75!520
27.514 -23.161 1.40 1.497
82 66.815 55.692 0.87 16 -259.290 1.22 1.79952
42.217 92.351 variable 18 x33. tr29 8.20 1.55963
61.219 -15.102 1.52 1.834
00 37.220 -37.89.3 0.10 21 2077.730. 2.55 1.83400
37.222 -102.532 l f x l =41.27=1.43L f wf
■=29.40=1.021- f wI f m
l =41.77=1.450- f wf P/=6
0.47-2.1oO-fwf, =867.5=
30.12- f wn 4n 3 = 0.297 n8~n 9 = 0.257 n 1 2 n 1 1 = (J, 2”141 r 19
1 = 15.102 = 0.524・f w [Example 3
1 FNO1: 4 f =;! 8. Ft~82.0r
d n L 35B, 042 3.37 1.67790 55
．． :'(2-1273,880,10 3141,1581,971,88300/10.84
31.662 7.32 5 -838.421 1.94 1. ．． 411749
70.16 26.583 5.85 1.805+
8 25. '17 49.448 Variable 8 52.0593.89 J, 137790 55
．． 39 -12/1.768 0.1.0 10 37.228 6.95. 1.729] 6 5
/1.711 30.945 1.77 1.8051
8 25. '412 785.392 Variable 13 50.586 2.33 J, 7fi182
26.614 -22.313 1. /10 1.51
[i:3:i 64.1], 5 58.770 0.7
8 16 -253.865 1.22 1.79952
42.21.7 99.861 Variable 18 96, 260 8.08 1, 5 (i87:1
till ]19 -15.752 1.49 J,
IL(4oo17.220 =42.978'0.1
0 21 -1.556.06 2.50 1.8:', /
! 00 37.222' -94,118 1f s I =40.30=1.39! l f wf
II =29.04=1.008・f wI f @
l =, 40.90 = 1.420 - f wf y
=60.25=2.092- f Wf 1 =886
．． 2=30.77・fwn a n 3 =0.31
8 n [+ 110 :0.245 n12 nl □ =0.265 1 r 19 1 =15.752 =0.547・f
lol

[Brief explanation of the drawing]

Figure 1 is a lens diagram of Example I, Figures 2 and 3 are aberration diagrams of Example 1 at the short focus side and long focus side, respectively, Figure 4 is a lens diagram of Example 2, and Figure 5 is a lens diagram of Example I. 6 are aberration diagrams on the short focus side and long focal point side of Example 2, FIG. 7 is a lens diagram of Example 3, and 8th and 1. FIG. 9 is an aberration diagram of the short focus side and the long focus side -C of Example 3, respectively. Fig. 1 Fig. 2 Sine condition Fig. 3 Sine condition Fig. 4 Fig. 5 I χ sine condition Fig. 6 Sine condition Fig. 2 Sine condition reaching bed

Claims (1)

[Claims] In order from the object side, a positive lens, a second lens, a negative meniscus second lens with a convex surface facing the object side, a negative third lens, and a bonded lens with the third lens. a fourth lens which is a positive lens; a fifth lens which is a positive lens; a fifth lens which is a positive lens; a sixth lens which is a positive lens; a first lens group consisting of a seventh lens which is a negative lens and which has positive refractive power as a whole; an eighth lens which is a positive lens;
a first lens group consisting of a negative ninth lens laminated with the eighth lens and a negative first O lens and having negative refractive power as a whole; a first positive lens; A first negative lens laminated with the first lens.
2 lenses and a 13th lens which is a positive lens, and has a positive refractive power as a whole,
A zoom lens that is an optical system that changes magnification by moving all of the four groups, and is characterized in that it satisfies the following conditions. (1) 1.1< I f ll / f w<1.7
, f<0(2) 0.8< f rr / f W
<1.2(3) 1.1<l fn+ l/fw<1.
7, fm<0(4) 1.8<f y/f
w<2.4(5) 8<f 1/f w<50(6
) n 4 n 3 )'0.2 (7) 1 day - n 9 ) 0.15 (8) nl 2 n+ + >0.2 (9) 0.4
5<l rl 9 l/fw<0.6, rl 9<O
fI: Composite focal length of the first lens group f■: Composite focal length of the ■th lens group f +u: Composite focal length of the 1st II lens group,
[f■: Synthetic focus j of the ■th lens group, I(j) folding f
w: Shortest focal length of the entire system fl: Focal length of the lens n,: Refractive index of the glass material used for the i-th lens r1. : Radius of curvature of the bonding surface of the first lens and the 12th lens