JPH02156215A - Copying lens system - Google Patents

Abstract

PURPOSE:To obtain a wide view angle and short focus lens and to miniaturize the subject system by forming a complete symmetrical type compact copying lens system having a wide view angle constituted of six groups and six pieces. CONSTITUTION:The lens system is provided with the first group of a positive meniscus lens whose convex surface is turned to an object side, the second group of a negative meniscus lens whose convex surface is turned to the object side, the third group of a positive meniscus lens whose convex surface is turned to the object side, and a diaphragm S in order from the object side of the left side. The lens system is constituted of the fourth group of a positive meniscus lens whose convex surface is turned to an image side being symmetrical to the third group by placing this diaphragm S inbetween, the fifth group of a negative meniscus lens whose convex surface is turned to the image side being symmetrical to the second group in the same way, and the sixth group of a positive meniscus lens whose convex surface is turned to the image side being symmetrical to the first group in the same way. That is, a complete symmetrical type lens system constituted of six groups and six pieces is formed. In such a manner, a focal distance is short, a view angle becomes wide, and the miniaturization of a copying machine can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a compact copying lens for a full exposure type copying machine.

"Prior Art" Currently, copying machines are strongly desired to be faster and more compact. Since a scanning type copying machine has a scanning movement mechanism, there is a limit to how high the speed can be increased. Further, problems such as spatial problems such as the total length and height of the optical system including the mirror scanning system and reduction in the number of parts of the scanning mechanism always arise. On the other hand, full-exposure copying machines can be faster than such scanning-type copying machines, and can be made smaller by using wide-angle and short-focus lenses. Moreover, the lens itself has a compact structure.

As such a lens system for a copying machine, for example, Japanese Patent Laid-Open No. 6
There are excellent lenses shown in Japanese Patent Application Laid-open No. 1-205901, Japanese Patent Application Laid-Open No. 61-210314, and Japanese Patent Application Laid-Open No. 62-47614, but each lens system has a structure of 6 groups and 6 lenses.
Half angle of view ω = 34° for element configuration, half angle of view ω = 8 elements in 4 groups
32'' consists of 8 elements in 3 and 6 groups and has a narrow half angle of view ω=41.5°, or has a large number of lenses.

The objective of the copying lens system of the present invention is to provide a compact lens system having a wide field angle of 42 degrees in half and a short focal length, although it is composed of 6 lenses in 6 groups.

[Means for Solving the Problems] In this invention, in order from the object side, a first group consisting of a positive meniscus lens with a convex surface facing the object side, a second group consisting of a negative meniscus lens with a convex surface facing the object side, and a second group consisting of a negative meniscus lens with a convex surface facing the object side. A third group of a positive meniscus lens facing the object side, an aperture S, a fourth group that is symmetrical to the third group across the aperture, a fifth group that is also symmetrical to the second group, and a fifth group that is also symmetrical to the first group. This is a completely symmetrical and compact copying lens system with a wide angle of view and is composed of 6 elements in 6 groups, including a symmetrical 6th group.

[Embodiment] The present invention will now be described in detail with reference to the drawings. For example, FIG. 1 is a cross-sectional view showing the configuration of a copying lens system according to a first embodiment of the present invention. A first group of positive meniscus lenses with the convex surface facing the object side, a second group of negative meniscus lenses with the convex surface facing the object side, a third group of positive meniscus lenses with the convex surface facing the object side, aperture S, A fourth group of positive meniscus lenses with a convex surface facing the image side that is symmetrical with the third group across this aperture; a fifth group of negative meniscus lenses with a convex surface facing the image side that is also symmetrical with the second group; It is a completely symmetrical lens system with six lenses in six groups, and a sixth group of positive meniscus lenses with a convex surface facing the image side, which is also symmetrical to the first group.

In such a lens system, the focal length of the entire system is f, and the focal length and power of the second lens group are f2*'f
'2 + focal length and power of the third group lens f3
+ 'f' 3 + Change the number of glass materials for the second and third group lenses.2. When C3, 1, 1f≦f2+f3 ≦2.3f... (1
)? 2 ν2 +y3 ν3 0, 1≦≦0.35...
Each conditional expression (2) is satisfied.

The above conditional expression (1) presents the aberration correction range,
If the upper limit is exceeded, astigmatism and coma, which are axial and extra-axial aberrations, will increase, making it difficult to correct them.
The Petzval sum is bad and the astigmatic difference becomes large.
If the lower limit is exceeded, astigmatism increases and correction thereof becomes difficult.

The above conditional expression (2) presents a correction range for chromatic aberration, and if this range is exceeded, lateral chromatic aberration and longitudinal chromatic aberration increase together, making it difficult to correct them.

Below, specific lens specifications of Examples 1 to 4 that satisfy such conditional expressions are shown in Tables 1 to 4, respectively, and the corresponding lens configurations are shown in FIGS. 1 and 3. , FIG. 5, and FIG. 7, and respective aberration curve diagrams are shown in correspondence with FIG. 2, FIG. 4, FIG. 6, and FIG. 8. In addition, each table above shows the radius of curvature and the distance between the top surfaces of the shafts.

The refractive index and Atsube number of the glass material at the d-line are shown for each surface.

Furthermore, the numerical values of the above conditional expressions for the first to fourth embodiments are summarized in Table 5.

(Margin below) Part 1 f=toO,o FNo, -10,0 Radius of curvature Axis top surface spacing rl　　21.05 d, 4.99 +2 31. Mouth 2 +1. 3.54 ry 16.88 d, + 1.43 +4 1 piece, 68 d, 4.99 rs　　　112.28 d+ 2.14 rr+ 89.14 dr, 1. :17 d? 3.17 +7 -89.14 do2.14 rQ　-az, za d94.99 rq -1:1. l1ll d, 0 1.4 pieces r. -16,88 d++ 1.64 rll　　　-31,02 d+t 4.99 r, , -2%, 05 Σd Snake 41.12 table Refractive index (Nd) N, 1.71 koO 1,7985 N.

1.5228 1.6228 1.79115 N.

1.71 ko0 7 tube number (rl1) ν1 53.9 ν2 22.6 56, g ν4 56, g ν1 22.6 6 53.9 3rd f-100, OFNO, proverb 1O00 radius of curvature axis Top distance rl 26.33 d, 7.12 rv 52.82 d, 1.42 ry :lO,0g d, 2.85 +4 19.6Jl d4 5.16 rs 85.85 d, 2.14 ra! 17.91 d6 3. core d7 co, core rt -97,91 (In 2.14 ra 45.85 d, 5.15 r, -19,68 d, a 2J5 rl.-: IO, U8 dll 1.42 rl1-52.82 dl a (νd) ν1 44.9 1 year old 22.6 Si1 64.2 ν4 64.2 ν1 Z2.G ν is also 44.9 2nd f-100, OF No, -10,0 Radius of curvature Upper axis distance rl22 .48°d+ 5.7+1 +2: 15.70 d, 3.06 rx 19.30 (131,78 r, + 14.96 d, 5.17 rs 82.68 d, 2.14 rl, 91.61 d, 3. Core d, Ko, 37 rt -91,61 do 2.14 ro 42.6δ d, 5.17 rs -14,96 dl.1.78 ",.-19,:10 dt+ 3.06 rl1 -35.70 d+* 5.7O r+* -22,48 ° Σd-42,44 Table refractive index (Nd) Atsube number (νd) Nl 1.71ko0 ν l 5ko, 9N! 1.7985 ν2 22.6 N.

1.5699 ν3 48.1 1.5699 ν4 48.1 N@ 1.7985 ν22.6 1.7130 White 53.9 4th r-100, OFNo, -10,0 Radius of curvature Axis top surface spacing rl 24 .26 d, 6. /II rQ '0.90 d, L14 ri 23.9G d, 2.49 +417.0? (L 5.16 +9 (11,91 ds 2.14 rs 9 ko, 06 d6 ko, 37 d? 3. core ", -93,06 d, 2.14 re 41.! 11 d, 5.16 rq -17, [17 11+o 2.49 ``1゜-23, d++ 2.14 rll -4], !lO d+z 6.41 rli -24,26 Σd-1fko, 42 Table refractive index (Nd) Atsbe number (νd) N, 1.7130 ν, 53.
9N 1.7985 22.6 Nri 1.5168 νko64.2 1.5168 ν4 64.2 s 1.7985 ν~ 22.6 1.7130 ν is also 5:1. ! 1 Table [Effects of the Invention] As explained above, the copying lens system of the present invention can correct both axial aberrations and off-axis aberrations, despite the ultra-wide angle of view q with a half-angle of about 42°. The lens is kept small and well-balanced, and the aberrations are well corrected.

In addition, since the lens system has a short focal length and a short overall lens length and has a small number of lenses, it can be applied to a full exposure type copying machine for A3 size originals, thereby reducing the size of the copying machine.

Furthermore, even though the number of lenses in the lens system is smaller than that of conventional lenses, it is possible to provide a wide angle of view, making it possible to provide an inexpensive lens system for copying machines.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the lens configuration of the first embodiment of the present invention, FIG. 2 is an aberration curve diagram of the lens system shown in FIG. 1, and FIG. 3 is a second embodiment of the present invention. 4 is an aberration curve diagram of the lens system shown in FIG. 3, FIG. 5 is a sectional view showing the lens structure of the third embodiment of the present invention, and FIG. , an aberration curve diagram of the lens system shown in FIG. 5 above, FIG. 7 is a sectional view showing the lens configuration of the fourth embodiment of the present invention, and FIG. 8 is an aberration curve diagram of the lens system shown in FIG. 7 above. It is a diagram. Figure 5 Patent applicant Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A first group consisting of a positive meniscus lens with the convex surface facing the object side in order from the object side, a second group consisting of a negative meniscus lens with the convex surface facing the object side, and a second group consisting of a negative meniscus lens with the convex surface facing the object side. A third group of a positive meniscus lens, an aperture S, a fourth group that is symmetrical to the third group across the aperture, a fifth group that is also symmetrical to the second group, and a sixth group that is also symmetrical to the first group. A completely symmetrical and compact copying lens system with a wide angle of view, consisting of 6 elements in 6 groups. 2. The copying lens system according to claim 1, which satisfies the following conditional expressions (1) and (2). 1.1f≦f_2+f_3≦2.3f...(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(2) However, f; focal length of the entire system f_2; focal length of the second group f_3; Focal length of the 3rd group ■_2; Power of the 2nd group ■_3; Power of the 3rd group ν_2; Abbe number of the glass material of the 2nd group ν_3; Abbe number of the glass material of the 3rd group