JPH0281016A - Lens for copying - Google Patents

Abstract

PURPOSE:To obtain a lens for copying which is bright with a vignetting factor of almost 100% and F number of 4 and, at the same time, well corrected in various aberrations by constituting the optical system of the lens of six lenses of six groups. CONSTITUTION:The optical system of this lens for copying is constituted of six lenses of six groups in such a way that the 1st- and six-group lenses are constituted of convex meniscus lenses 10 and 20 having the same optical property and the 2nd- and 5th-group lenses are constituted of concave meniscus lenses 12 and 18 having the same optical property. The 3rd- and 4th-group lenses are constituted of convex meniscus lenses 14 and 16 having the same optical property and the lenses are perfectly symmetrically arranged about a diaphragm 15 provided at the center. In addition, nonspherical surfaces are adopted to the convex surfaces of the 1st- and 6th-group lenses are concave surfaces of the 2nd- and 5th-group lenses and this lens system is constituted so that the system can satisfy the conditions of Inequalities (I)-(III). The K1, K2, and K3 of the inequalities respectively represent the cone constants of the convex surfaces of the 1st- and 6th-group lenses, concave surfaces of the 2nd- and 5th-group lenses, and concave surfaces of the 3rd- and 4th-group lenses.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a copying lens.

[Prior Art] Various types of copying lenses have been proposed and known for forming an image of an original onto a photoreceptor in a copying machine. In a copying machine, since the imaging magnification is basically equal to the same magnification, a copying lens is often used in which a plurality of lenses are arranged approximately completely symmetrically around an aperture. A comparatively slow lens of this type is the FN04 described in Japanese Patent Publication No. 10091/1983.
．． 5, which has 6 elements in 6 groups, is known.

[Problems to be Solved by the Invention] On the other hand, there is a strong demand for copying machines to improve copying speed and reduce power consumption. To meet this demand, a bright copying lens is required.

If you try to achieve a copying speed of about 80 sheets per minute without increasing the original illumination energy, the above FN
The 84.5 copying lens is not bright enough, so F
A brighter lens of about No. 4 is required.

The present invention was made in view of the above-mentioned circumstances, and
The objective is to provide a copying lens that has a larger aperture than FNO4 and has unprecedented high performance.

[Means to solve the problem] The present invention will be explained below.

The copying lens of the present invention has a structure of six lenses in six groups in which the first to sixth groups are arranged in this order from the object side to the image side, and has an aperture between the third and fourth groups.

As shown in FIG. 1, the first group is a convex meniscus lens 10 arranged with its convex surface facing the object side, the second group is a concave meniscus lens 12 arranged with its convex surface facing the object side, and the third group is a convex meniscus lens 10 arranged with its convex surface facing the object side. The convex meniscus lens 14 is arranged with its convex surface facing the object side, the fourth group is a convex meniscus lens 16 which is arranged with its concave surface facing the object side, and the fifth group is a concave meniscus lens arranged with its concave surface facing the object side. The lens 18 and the sixth group are convex meniscus lenses 20 arranged with their concave surfaces facing the object side, and an aperture 15 is arranged between the convex meniscus lens 14 of the third group and the convex meniscus lens 16 of the fourth group. Ru.

The convex meniscus lens 10 of the first group and the convex meniscus lens 20 of the sixth group are optically the same, and the concave meniscus lens 12 of the second group and the concave meniscus lens 18 of the fifth group are also optically the same, The third group of convex meniscus lenses 14 and the fourth group of convex meniscus lenses 16 are also optically the same lenses. These first to sixth groups are arranged approximately completely symmetrically about the aperture 15.

Aspherical surfaces are adopted for the convex surfaces of the first and sixth groups, the concave surfaces of the second and fifth groups, and the concave surfaces of the third and fourth groups, and the conic constant of the convex surfaces of the first and sixth groups is Assuming that is 1, the conic constant of the concave surfaces of the second and fifth groups is 2, and the conic constant of the concave surfaces of the third and fourth groups is 3, these are (I) -0,003<k , <0.001(II)
0.006<k2<0.007(III) 0.2
The condition <k3<0.4 is satisfied.

[Effect] Normally, when a lens becomes brighter, coma flare increases and imaging performance deteriorates. In a so-called orthometa type lens consisting of 6 elements in 6 groups, if the aperture efficiency is 10 oz, in a combination of spherical lenses, the FNO is 4 as in the conventional technology.
．． 5 was the limit.

In the present invention, the aperture efficiency is approximately 100χ. In order to achieve a lens as bright as 4, aspheric surfaces were used for the convex surfaces of the first and sixth groups, the concave surfaces of the second and fifth groups, and the concave surfaces of the third and fourth groups.

The conic constants of these aspheric surfaces are based on the above conditions (I) and (II).
, (III). These conditions (I) ~
By satisfying (III), it is possible to achieve FNo. 4 and also to satisfactorily correct coma aberration. If each condition is exceeded, coma aberration increases and imaging performance deteriorates.

[Example code] Three specific examples are listed below.

In each example, rl is the radius of curvature of the first surface from the object side (including the aperture surface) as shown in FIG. 1, d is the distance between the first surfaces from the object side, and focal length of the system, F
NO represents brightness, ω represents a half angle of view, and Y represents object height. Also,
*mark indicates an aspherical surface.

Example 1 f=260. FNO"4. ω"22.3 degrees, Y=2
16mm1 r + d; J
nj vj87.421 21.785 1
1.74400 44.792239.558 2.1
60 Do 3 1726.757 8.183 2 1.6
4769 33.804” 64.847
3.3125 96.468 10.281 3
1.72000 50.256” 145.9
75 11.7797 (1) (Aperture) 11.779 8' -145,97510,28141,720
0050,259-96,4683,312 10"-64,8478,18351,6476
933,8011-1726,7572,160 12-2239,55821,78561,74400
44,7913"-87,421 Aspheric r,: k+"-0,002578, A,"-2,71
0260'l0-9A6=2.623810・10-1
2. As=7.999070.1O-16A,. =-
5,386590・1O-19r4:kz”0.o08
392, A4”1.38324040-9A6=2
．． 250550・10-”, A,=-1,09410
0・IQ-14A+o"-1,585240・IQ-"
ra: k3”0.225591, A,”8.34
0200'IO-"Aa"2.405970-IQ-"
, Aa"-9,760930・1O-16A+o"-
3,434690-10-”r8: k3”o, 225
591, A4"-8, 34020040-9A6
=-2,405970-10-”, A8=9.76
0930・IQ-16A+o”3.434690・10
-"r+o: kz"o, o06392, A4"
-1,383240-10-9A6=-2,25055
0・10−”, A,=1.094100・10−1
4A. =1.585240・10-17r, 3:
k,”-0,002578,A,”2.710280・
lo-9Aa"-2,623810'l0-12.
Aa"-7,999070'lO-"A,O=5.38
6590・10-19 Example 2 f =260. FNo” 4. ω:l: 22.3 degrees,
Y=216mmrid+Jn
J ν.

87.353 21.858 1 1.74400 4
4.793432.779 1.857 2052.530 8.504 2 1.64769
33.8065.223 3.224 95.740 10.222 3 1.72000 5
0.25140.765 12.035 co (aperture') 12.035 8" -140,76510,22241,720
0050,259-95,7403,224 10"-65,2238,50451,6476
933,8011-2052,5301,657 12-3432,77921,85861,74400
44,7913"-87,353 Aspheric r: k,"-0,001028,A4"-2,33
1360・1O-9Aa ”2.865350・10-
+2. Aa'9.811790・1o-16A,. =
-6,444700-10~19r4: k2”o, 0
06452, A4"1.775410'1O-10
A, =2.858120・10-”, As=-1,
470690・10-”A10=-1,6946804
0-” RA: 3” 0.316016, A4” 1.223
270・1O-8Aa"2.967380・10-",
Aa"-3,801790・1O-15A, .=-
5,574630-10~19rs: k, = 0.31
6016, A, "-1,223270'1o-8゜80・-2,967380・10-", A8=3.8
01790・10-15A, O=5.574630・1
O-19rho: k2”o, o06452, A4
”-1,775410・1O-10A6=-2,858
120-10-”, A8=1.470690-10-
14A+o4.694680・IO-” r, 3: k+”-0,001028, A4”2.33
1360'IO-'A6=-2.865350・10-
12. As=-9,811790-10-"A+o"
6.444700・10-19 Example 3 f=260. FNO"4. ω: 22.3 degrees, Y=2
16mmr, d i J n ; ν.

87.264 21.902 1 1.74400 4
4.794178.164 1.395 2135.977 g, 680 2 1.64769
33.8065.307 3.188 95.285 10.200 3 1.72QO050
,25138,38712,136 00 (aperture) 12.136 -138.387 10.200 4 1.72000
50.25-95.285 3.188 -65.307 8.680 5 1.64769 3
3.802135.977 1.395 -4178.164 21.902 6 1.7440
0 44.7913"-87,264 Aspheric rl: k+"o, ooo169, A4"-1,9
8387040-9A, =2.914690・10-1
2. A8=1.041080・10-”A+o”-6
,64915040-" r4: k2"0.006462, A4"-
1,668830・IO-”.

A6=3.040350・10th, A8=-1,6
45100・IQ-14A10=-1,679610-
10-+7r, ,: k, l”0.355431
, A44.41057040-8A, =3.190
010・10-”, Aa=5;096240・10-
"A+o"8.44956040-" rs: k3"o, 355431, A4"-1,4
10570'1O-8A6=-3,190010・10
-”, A, = 5.096240・10A+o”-8,
449560・10-”rlo: k2”o, 0064
62, A4:1.66883040-10A, =-
3,040350-10th, A8=1.64510
0.10-"A+o"1.679610'l0-17r
,,: k,"0.000169, A4"1.96
3870'l0-9A6=-2,914690・10-
12. Ai+=-1,041080・1O-15A+
o"6.649150'lO-" FIG. 2 shows an aberration diagram regarding Example 1. Also, the third
The figure shows an aberration diagram for Example 2, and FIG. 4 shows an aberration diagram for Example 3.

In each aberration diagram, SA, SC are spherical aberration and sine condition, DS, DM are astigmatism, DIST is distortion (z),
COMA indicates meridional coma aberration.

The solid line of astigmatism relates to the sagittal ray, and the broken line relates to the meridional ray. Also, ■ is d-line (587, 56 nm),
■: F line (486,13 nm), ■: C line (656,2 nm)
7 nm).

[Effects of the Invention] As described above, according to the present invention, a novel copying lens can be provided.

Although this copying lens has a small number of lenses with a 6-element structure in 6 groups as mentioned above, it is very bright with an aperture efficiency of approximately 100χ and an FNO of 4 due to the adoption of an aspheric surface, and it effectively corrects various aberrations. In particular, coma flare can be kept to a very low level, and the contrast is high from on-axis to off-axis.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the lens configuration of the copying lens of the present invention, and FIGS. 2 to 4 are aberration diagrams regarding Examples 1 to 3, sequentially. 10. First group convex meniscus lens, 12. ,',
Second group concave meniscus lens, 14. , , third group convex meniscus lens, 15. , ,Aperture, 16. ,
, fourth group convex meniscus lens, 18. , 5th group concave meniscus lens, 20. , , 6th group convex meniscus lens δ diagram) 7?341

Claims (1)

[Claims] The first to sixth groups are arranged in this order from the object side to the image side, and there is an aperture between the third and fourth groups, and the first group has a convex surface facing the object side. The second group is a convex meniscus lens with its convex surface facing the object side, the third group is a convex meniscus lens with its convex surface facing the object side, and the fourth group is a convex meniscus lens with its convex surface facing the object side. The convex meniscus lens in the 5th group is the same as the 3rd group with its concave surface facing the object side, the 5th group is a concave meniscus lens that is the same as the 2nd group with its concave surface facing the object side, and the 6th group is a concave meniscus lens with its concave surface facing the object side. The lens is a convex meniscus lens that is arranged toward the diaphragm and is the same as the first group, and the first group to the sixth group are arranged almost completely symmetrically with respect to the aperture, and the first group and the sixth group are Aspherical surfaces are adopted for the convex surfaces of the group, the concave surfaces of the second and fifth groups, and the concave surfaces of the third and fourth groups.
When the conic constant of the convex surfaces of the group and the sixth group is k_1, the conic constant of the concave surfaces of the second and fifth groups is k_2, and the conic constant of the concave surfaces of the third and fourth groups is k_3, these are ( A copying lens characterized by satisfying the following conditions: I) -0.003<k_1<0.001 (II) 0.006<k_2<0.007 (III) 0.2<k_3<0.4.