JPS5812567B2 - wide angle zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a front group with negative refractive power and a rear group with positive refractive power, and magnification is changed by changing the distance between the front group and the rear group. It is related to a zoom lens, and although it has an extremely simple configuration of 7 elements in 6 groups, the zoom ratio is approximately 2.
It is an object of the present invention to provide a zoom lens which has an angle of view of about 63 degrees at the double and wide end, and which can correct various aberrations in a well-balanced manner.

The configuration of the present invention will be explained below with reference to the attached drawings. As shown in FIGS. 1 and 5, in order from the object side, the front group ■ has a negative refractive power and the rear group ■ has a positive refractive power. In a zoom lens that performs magnification by changing the air gap between The rear group (2) is composed of, in order from the object side, a fourth lens group of convex lenses, a fifth lens group of cemented concave meniscus lenses of convex lenses and concave lenses, and a convex meniscus with a convex surface facing the image side. and a sixth lens group of lenses, and is characterized by satisfying the following conditions.

(1) 0.1 < n6 n5 < 0.35 (2
) 0.55 f l<l rlQ l<0.85 f
l(3) 0.3fn <d, +d1o<0.4
fn(4) 0.4fn < r,, <0.5
fll However, n5, n6: Refractive index of the glass of the convex lens and concave lens of the fifth lens group, respectively f■: Composite focal length of rear group ■ only d9+d1o: Composite thickness of the fifth lens group r10: Cemented surface of the fifth lens group radius of curvature r11: radius of curvature of the image-side surface of the fifth lens group Next, each of the above conditions will be explained in detail.

Condition (b) is related to the correction of the Petzval sum,
If the difference in refractive index between the concave and convex lenses in the fifth lens group is smaller than 0.1, the Petzval sum will be negative and large; if it is larger than 0.35, the Petzval sum will be positive and too large. This also makes it difficult to correct field curvature.

Condition (2) relates to correction of spherical aberration, and since Jto has a concave surface facing the aperture, it is mainly useful for correction of spherical aberration.

When lr10l becomes smaller than 0.55f■, spherical aberration becomes over-corrected, and conversely, when lr10l becomes larger than 0.85f■, spherical aberration becomes under-corrected.

Condition (3) is intended to bring the front principal point of the rear group (2) closer to the object side and to correct astigmatism and distortion in a well-balanced manner.

In order to make the lens system compact and to provide the front group 1 and the rear group (2) with an appropriate refractive power arrangement that facilitates aberration correction, it is necessary to move the front principal point of the rear group (2) closer to the object side.

To achieve this, it is sufficient to bring the 9th surface of the 5th lens group, which has positive refractive power, as close as possible to the 4th lens group, and to bring the 11th surface, which has negative refractive power, toward the image side. 1
It is sufficient if the distance between one surface, that is, d9+d10, is 0.3 f■ or more.

Furthermore, if the 11th surface is far from the aperture, the height of the principal ray incident on the 11th surface will become higher, which is effective for correcting barrel distortion at the wide end, but d9+d10 is 0.4
When the value is larger than f■, the curvature of the meridional image plane becomes large and correction becomes difficult.

(4) is a condition for correcting astigmatism and distortion in a well-balanced manner in relation to (3), and the radius of curvature r11 of the eleventh surface located at the position specified in (3) is 0.4f■ As the size becomes smaller, the curvature of the meridional image plane increases,
On the other hand, if it is larger than 0.5f, it becomes difficult to correct barrel distortion at the wide end.

Next, examples of the present invention will be shown.

Example 1 f-1~1.3 8 9 A-1.9 0 6 Back focus 1.17 2~1.4 3 2~1.7 7
7rl 1.7347 dt O. 0417 n, 1.71300ν, 53
．． 9r20.6838 d20.2283 r3 -4.3992 ds O. 0333 n2 1.60311 ν26
0.7r4 1.0652 d, 0.0625 ? 5 1.0137 d O. 1389 n3 1.74400 v
344.75 r6 41.1759 d61.1545~0.5163~0.0714r7
1.6252 d70.0778 n4 1.71300 ν,
53.9r8-2.9372 d80.0056 r9 0.6700 d, 0.4208 rl5 1.51742 ν
, 52.3r 10 0.7740 d O. 0417 1.74000 ν62
8.310 n6 rll O. 5732 d10.2161 r1-4.3114 d, 20.0778 n7 1.74950!
/735.3rl3 -0.9262 flI-1.234 lrto l-0.627f II, r1B-0.4
65 flId, 10 ct, o-0.3 7 5 f II
Example 2 f-1~1.389~1.906 Back focus 1.141~1.391~1.7 2
3rl 1.6503 d O. 0417 fJ 1.69350 ν,
53.21 r2 0.6736 d20.2465 r3 -3.6472 d O. 0333 1.60311 ν260
．． 73 n2 r4 1.1583 d40.0543 r5 1.0335 d O. 1528 n3 1.70154 v341
．． 15 r6 -27.7456 d61.1995^0.5367~0.0745r7
1.7112 d O. 0917 1.69350 ν453.
2? n4 r8-2.2452 d80.0056 rg O. 6520 do O. 2362 n5 1.53172 ν, 4
8.9rto -1.0242 d,0 0.235I n6 1.72151 ν6
29.2r 11 0.5279? 1, 0.2121 r1-3.221 1 d120.0778 rl7 1.701s4
ν741.1rl3 -0.9458 fn-1.233 lrtol-0, 831fll, rH-0.428
fnd, 10d, o- 0.3 8 2 f II

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of Example 1 of the present invention, and FIGS. 2 to 4 are aberration curve diagrams of spherical aberration, astigmatism, and distortion at the wide end, intermediate, and telephoto end of Example 1, FIG. 5 is a block diagram of a second embodiment of the present invention, and FIGS. 6 to 8 are aberration curve diagrams at the wide end, intermediate end, and telephoto end of the second embodiment.

Claims (1)

[Claims] 1. Consisting of a front group I having a negative refractive power and a rear group ■ having a positive refractive power in order from the object side, and changing the air distance between the front group I and the rear group ■. In a zoom lens that changes magnification with The rear group y includes, in order from the object side, a fourth lens group of a convex lens, a fifth lens group of a cemented concave meniscus lens of a convex lens and a concave lens, and a sixth lens group of a convex meniscus lens with a convex surface facing the image side. A wide-angle zoom lens comprising: a wide-angle zoom lens that satisfies the following conditions; (1) 0.1 < n6-n5 < 0.35 (2
) 0.5 5 f M< l rlQ l<0. B
5 f 1(3) 0.3 f II <d, +d
1o<0.4 f n(4) 0.4fll<
rtt <0.5fl However, n5, n6: Refractive index of the glass of the convex lens and concave lens of the 5th lens group, respectively f■: Composite focal length of only the 9th group ■ d9+d10: Composite thickness of the 5th lens group r10: 5th lens Radius of curvature of the cemented surface of the group r11: Radius of curvature of the image side surface of the fifth lens group