JPS5964809A - Wide angle lens - Google Patents

Abstract

PURPOSE:To provide a wide angle lens, where the telephoto ratio is low and aberrations are compensated well, only with spherical faces, by constituting a lens system with four lenses divided to four groups and satisfying specific conditions. CONSTITUTION:The lens system is constituted with the first group of a double convex lens whose stronger convex is directed to the object side, the second group of a double concave lens whose strong concave is directed to the image side, the third group of a double convex lens, and the fourth group of a negative meniscus lens which are arranged in order from the object side, and conditions of expressions 1-4 are satisfied when the focal length of the whole of the system, the resultant focal length of the first and the second groups, the resultant focal length of the first, the second, and the third groups, the interval between the third group and the fourth group, the radius of curvature of the object-side face of the fourth group, and the refractive index of the glass material of the first group are denoted as (f), f1.2, f1.2.3, D6, R7, and Ni respectively. Thus, the telephoto ratio is held down to <=1.2 without aspherical faces to attain a wide angle lens where aberrations are compensated well.

Description

Detailed Description of the Invention The present invention is a wide-angle lens with an angle of view of about 57 degrees and a brightness of F2.8, particularly a wide-angle lens that cannot be used in optical systems with relatively small screen sizes such as disk cameras and facsimiles. Regarding.

Conventionally, this camphor lens system had a small focal length, so no consideration was given to making the lens compact, and it was used as a large telephoto lens.
had. Recently, lenses for disc cameras have appeared that use aspherical surfaces to reduce the telephoto ratio.

The present invention has a configuration of 4 elements in 4 groups, and achieves an average of -1 in terms of spherical surfaces without using an aspherical surface. The objective is to obtain a wide lens with a low aberration rate and a good 1/C limit for the above-mentioned applications.

In order to achieve this objective, the lens system Vi consists of a first lens group consisting of a biconvex lens with a strongly convex surface turned toward the object side in order from the object side η, a biconvex lens with a strongly concave surface k F) 7 second lens f4f, 31/lens solution which is a biconvex lens, and 1'J84 lens tl' which is a negative meniscus with a convex surface facing the 1st quadrant 1111.
5, f: Focal length of all threads, fl, 2: Combined focal length of the Narulens group and the second lens, fl, 2゜3: From the 1st Luns group to the 3rd lens group -t composite focal length 1], h: Distance R7 between the third lens cup and the fourth lens group:
Object side curvature half value N1 of the fourth lens group: -o, o5/f <'<f 1.2<o, +5/f
・・・・・・ (1) 1.27/f ＜'＜f
l, 2.3 <1.55/f...
(2) (1,22f (D6 <0.36f
...... (3) N1, N2, N4>1.
75, N 3 > 1.68 . . . With a lens that satisfies each condition (4), the telephoto ratio can be kept to about 12 or less.

In the lens of the present invention, an aperture is placed between the second lens 1 and the third lens group in order to improve the conditions for off-axis light flux. Therefore, the negative distortion generated in the third lens group can be reduced by
This is corrected by using a biconvex lens in the lens group.

Conditions (1) and (2) are necessary to keep spherical aberration, coma aberration, and distortion correct and to reduce the telephoto ratio.

If the lower limit of the condition ([) is exceeded, the focal length of the Luns group becomes longer, but the focal length of the second lens group becomes shorter, so the principal point is placed at zero focus, where over coma flare and large under distortion occur. Since 1i is transferred to +a a+, the telephoto ratio increases. Conversely, if the upper limit is exceeded, the lunes group V
) If the focal length becomes shorter or the focal length of the second lens becomes longer, large under-spherical aberration will occur.If the lower limit of (2) is exceeded, over-coma flare will occur, making it even more telephoto. On the other hand, if it is larger than the projection ratio, under-coma flare, large under-distortion aberration, and under-spherical spherical aberration will occur.

gI! Condition (3) Various aberrations f [necessary in order to keep the telephoto ratio small while keeping it within the appropriate range! These are the conditions.

If f't' (3) exceeds the lower limit, in order to keep the telephoto ratio small, '/f+,2 should be greater than the upper limit of all conditions (1)'/f S, 2.5 as the condition ( 2) must be greater than the upper limit.Conversely, if condition (3) exceeds the upper limit, the telephoto ratio will decrease, but the fourth lens group will be far away from the third lens group, resulting in a sphere Ii'i yield Correcting coma aberration becomes difficult.

In addition to keeping the perapard sum of the entire system true @ curve, the spherical aberration and coma aberration fIl! ! This is a necessary condition for keeping the lens within the correct range, as well as a necessary condition for keeping the telephoto ratio small. Refraction of convex lens group #AN1, N3
When becomes smaller than the lower limit, the half value of the curvature of the convex lens group becomes small, so the perapearl sum becomes large, and 1#! Surface curvature increases. Furthermore, spherical aberration becomes undercorrected.

Conversely, when the refractive indices N2 and N4 of the concave lens group become smaller than the lower limit of condition (4), the curvature half it of the concave lens group becomes small, so the perapal sum becomes small, and the image plane curves toward the lens group, resulting in astigmatism. As the distance difference increases, excessive coma flare occurs.

Even if the refractive index of each lens group is smaller than the lower limit of PI: (4), each aberration can be well corrected, but since the present invention is aimed at a lens system with a small focal length,
The ease of processing each lens group must also be considered.

If the refractive index of the convex lens group becomes smaller than the lower limit of condition (4), the aforementioned aberrations will occur. This is because when the refractive index of the concave lens group becomes small, the half value of the curvature of the convex lens group becomes small, so unless the axial thickness of the convex lens is increased, the lens processing will be difficult. However, 1 on the axis of the convex lens group! If jL1fr is increased, the telephoto ratio of the lens system cannot be kept small.

Historically, in order to keep the spherical gL difference and comatic aberration within appropriate ranges, it is desirable that %'7 satisfy the following conditions -0,4f<7<-o32f
(5) All examples of the lens system of the present invention will be shown below.

Next, examples of the present invention will be shown.

In the actual MIAVAJ, R is the radius of curvature, D is the interplanar distance, N is the refractive index, V is the Abbe number, and T is the telephoto ratio.

Example 1 f"l LI F'No=2.87 2w=573u
T = 1.197 1/f7.2=00538/f
'/f,, 2.3=1.4681/f 1 astigmatic convergence in spherical convergence, distortion convergence I term is λ, shown in the garden -j.

Example 2 f”ILJ FNo=2.87 2W=5724T=
1.198'/f,, 2=0.0415/f'
/f,,2. ．． =1.452/f spherical aberration, astigmatism,
The distortion aberration curve is shown in the third country.

Example 3 f=llJ FNo=2.87 2W=5731T=
1.199'/f -00982/f'/f
,,2. ．． -14688/f1.2- The spherical aberration, astigmatism, and distortion aberration curves are shown in 41!1.

(9) Example 4 f='it) FNo=2.872W=5726T=
1.195 1/f1.2=o, L) 181/f'
/f1.2. s=1.43uu/f Spherical aberration, astigmatism, and distortion aberration curves are shown in FIG.

(lO) Example 5 f”10 FNo=2.87 2W=57 32T=
1.199''/f =00312/f'/f
5,2.5=1.45 (JO/f1.2 Spherical aberration, astigmatism, and distortion aberration curves are shown in Figure 6.

(11) Example 6 f=lOFNO=2.87 2W=5626T=1.1
88'/f = Ou681/f'/f,,2
．． ．． =1.4143/f1.2 Spherical aberration, astigmatism, and distortion convergence curves are shown in FIG.

IIJ- Example 7 f”l U FNo=2.87 2W=5612T=
1.1561/f,=0.1241/f l/f1.
2. ! S=1.4734/f The spherical aberration, astigmatism, and distortion aberration curves are shown in FIG.

(13) tr Example 8 f=lu FNo=2.87 2W=5612T=
1.196'/f -0,0599/f'/
f, 2. ．． =1.3523/f1.2- Spherical aberration, astigmatism, and distortion aberration curves are shown in the q sub.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a lens of one implementation row of the present invention, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG.
Figureμ Example 15 Example 2, Example 3, Example 4 respectively
, Example 5, Example (14) It is an aberration curve diagram of Ushio 116, Example 7, and Example 8. Special chin person Roku Konishi Photography Industry Co., Ltd. Applicant's agent Patent attorney Fumio Sato (and 1 other person) (15) No. 1 Figure-50- Distortion aberration No. 7 Nu: Spherical positive aberration Non-exclusive aberration -0,1 (10,1-0,100,1 Spherical [I'T1 aberration Non-1, aberration distortion aberration distortion aberration No. 9 Figure 51- Distortion aberration procedure ) October 2-1, 1981 Director of the Special Budget Agency 1 Kazuo Wakasugi 1, Kakebe's following statement 1981 Tokuto Age No. 174467 2 Title of the invention Hiroceramics 3, Amendment. Patent applicant 1+:, F9 "Bund address: 1-26 Nishi 11-shuku, 1-shuku-ku, Tokyo
Name (127) Konishi Rokusha ＾ Koumami Shikikai Odai Rokusha
Kawamoto fl 4, agent 〒10
5 5. Number of inventions increasing due to sleeve jL None 6. Details of the subject of the amendment 7. Gatekeeper of amendment Attached sheet details of the amendment! ILl oath 3rd member line 15 to line 16 -o, o5
/f<1<f<o, 15. ＃・・・・・・
・ (1) 1.2 1.27/f<1<f 1.2.3<1°55/f
・・・・・・ Low o, o that supplements (2) as follows υ 5/f<1/f y2<0.15/f
・・・・・・ (1) 1.27/f<”/f 1.2
．． 3<1.55/f ・・・・・・(2) Procedure
Amendment oath (spontaneous) December 16, 1980 Commissioner of the Japan Patent Office 1 Kazuo Wakasugi 1, Incident 1981 Special Report No. 174467 2, Title of invention Wide-angle lens 3, Ministry of correction Relationship with ↓ Notes Patent applicant residence: Mingzhu Fudu Liao 1-ku Xixin Yen I 1, 26, 2, 4, agent 〒105 5, number of inventions increased by amendment None 6 徊]
positive object details jar

Claims (1)

[Claims] In order from the object side, the AIV lens group consists of a biconvex lens with four strong convex surfaces facing the object side, the second lens group consists of a biconcave lens with a strong concave surface facing toward the object side, and the second lens group is a biconvex lens. It is composed of a 3-lens curve and a 4th lens group which is a negative meniscus with its convex surface facing the image side, f: focal length of the entire system f+, 2: combined focal length t of the 4th lens meter and the 2nd lens group. S, 2.5: Composite focal length from the 4th lens meter + to the 3rd lens group D6: Distance between the 3rd lens group and the 4th lens meter Ry:
Object side curvature half value Ni of the 4th lens group: -0, o5/f <'/f1.2 <0.15/f when the glass material of the i-th lens group is taken as a force
1.27/f <'/f1.2.3 <1.55/
f(1,22f <D <0.36fN1
, N2 , N4 > 1.75 N3 > 1.68
A wide lens that satisfies all the conditions of