JPS6375720A - High-density gaussian lens for color - Google Patents

Abstract

PURPOSE:To read a wide color original of 12 inches with high density without any deviation among colors by composing a lens system of six lenses in four groups and satisfying specific conditions. CONSTITUTION:The lens system consists of the six lenses in the four groups. Then conditional inequalities hold, where n1, n2...n6 and v1, V2...v6 are refractive indexes and Abbe numbers of the 1st - the 6th lenses, (f) the focal length of the whole system, f1 the focal length of the 2st lens, and f123 the focal length of the 1st - the 3rd lenses. Consequently, the high-preformance lens is obtained which reads the wide color original of 12 inches exceeding A3 size with high density so that deviation in lateral power among colors is extremely small.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a color document reading lens for facsimiles, copying machines, etc.
This invention relates to a color high-density Gaussian lens with a half angle of view of about 18 and an F number of about 4.5, which has a half angle of view of about 18, an F number of about 4.5, chromatic aberration, and various aberrations that are well corrected, and which is composed of 6 elements in 4 groups and is targeted at originals of 2009.

(Prior art) A lens is used to reduce the original size, and the light receiving surface (for example, CC
In reading optical systems that form a reduced image on the light-receiving surface of a solid-state image sensor (such as D), the density of light-receiving elements is becoming higher. Attempts have also been made to read color originals by using high-density lenses with high resolution to separate light into the three primary colors of red, blue, and green.

After the reading light from a color document passes through a lens, it is separated into three primary colors, red, blue, and green, by a color separation prism, and then used as a light receiving element for high-density solid-state photography. The applicant has already proposed a high-density lens for reading documents using an open element, but this lens is intended for Fi, A4-size manuscripts, and is used for high-density color manuscripts exceeding A3-size manuscripts. It is difficult to read.

In the case of color originals, a wider wavelength range is usually required compared to monochrome originals, for example, from C-line to H-line.
Correcting aberrations is extremely difficult because it is necessary to make the imaging point the same and the image height equal for the three color wavelength bands of red, blue, and green, and to maintain performance above a certain level.

Furthermore, for example, if a solid-state image sensor with a pitch of 7 μm is used on the image plane, a solution of 714 lines/fl on the image plane requires force, so the axial chromatic aberration for each color should be minimized, and It is difficult to make the imaging point flat all the way to the periphery.

(Problems to be Solved by the Invention) As described above, until now, it has not been easy to obtain a lens for reading color originals larger than A3 size with high resolution.

The present invention has been made to solve this problem, and has a Gaussian lens arrangement of 6 elements in 4 groups in front of the 3-color separation prism, so that the main wavelengths of red, blue, and green can be 5QQnm
, 45Qnm, 545, and Q7nm, give appropriate refractive index and Abbe number to the convex lens of the lens, and also
~ By giving the third lens an appropriate refractive power, we can reduce the sum of the Bev Tuvars and reduce the difference in image height that causes color shift, that is, the chromatic aberration of magnification, which allows us to reduce the size of the image by 12 inches (304 The object of the present invention is to provide a color high-density Gauss type lens that can read color originals of 8 ttm) with high density.

(Precautions to Solve the Problem) The structure of the lens according to the present invention is as shown in FIGS. 1, 4, 7, and 10. The second group consists of a first lens of a convex meniscus lens with its convex surface facing the object side and a third lens of a concave meniscus lens, or a cemented lens of a biconvex lens. A cemented lens of a second lens and a third lens of a biconcave lens, a cemented lens of a fourth lens of a concave meniscus lens and a fifth lens of a convex meniscus lens in which the third group has a convex surface facing toward the outside; , consists of a cemented lens consisting of a biconcave fourth lens and a biconvex fifth lens, an aperture is placed between the second and third groups, and the fourth group is a convex lens with its convex surface facing the image side. In a lens consisting of the sixth lens of a meniscus lens and having a total structure of six elements in four groups, n4, n2...n6; C2...ν
6 is the refractive index and Atsube number of the first to sixth lenses, f is the composite focal length of the entire system, f is the focal length of the first lens, and fl-2 and fl-3 are from the first lens to the third lens. When the focal length is (2) 1.69<n2<1.86. 57.0>
ν2 )42.0(3) 0.73<f/f+<0
．． 92(4) 0.53<flf1-2. s<0.
70(5) 1.66<n5<1.86,58.0>
It is a color Gaussian lens that satisfies the fI+ of ν, :)42.0.

The three-color separation prism is placed behind the fourth group.

(Function) To explain in detail the contents of each of the above conditions, condition (1) is a condition necessary to reduce the value of field curvature, that is, the Petzval sum, and the refractive index of the first lens and the sixth lens. When the modulus is set to 1.75 or less, it becomes difficult to correct the curvature of field.

If ν1 is set to 43.0 or less, glass t- with a small Atbe's number must be used for the concave lens in order to correct chromatic aberration, and the Petzval sum cannot be made small. Furthermore, in order to correct chromatic aberration, the radius of curvature of the cemented surface becomes large, and the edge thickness becomes small, making processing difficult. Conditions (2) and (5) both indicate the range of the refractive index and Abbe number of the convex lens of the cemented lens; if the lower limit of the refractive index and the upper limit of the Abbe number are exceeded, the image height will be high. At some points, the meridional ray becomes negative and the performance deteriorates. On the other hand, if the upper limit of the refractive index and the lower limit of the Abbe number are exceeded, the meridional ray becomes too positive at high image heights, which is not appropriate. Condition (3) indicates the range of refractive power of the first lens.

When the upper limit is exceeded, spherical convergence becomes positive and astigmatism becomes negative, and when the lower limit is exceeded, the /< lance of the bonded iron surface becomes poor. Condition (4) indicates the range of refractive power from the 3rd lens to the gg3 lens; when the upper limit is exceeded, the chromatic aberration is negative, and the Petzval sum and distortion are large; when the lower limit is exceeded, the opposite is true. The range is appropriate.

(Examples) Four examples of the Gaussian lens of the present invention as described above are shown below.

The meanings of the symbols are as follows.

f: Synthetic focal length of the lens system (e-line) fl: Focal length of the first lens f1, 2-3: Focal length from the first lens to the third lens m: @Ratio ω: Half angle of view r: Radius of curvature d: Planar spacing n Nigarasu refractive index (e line) ν: Nigarasu Atsubbe number (e@) The suffixes of r, d, n, and ν are shown in Figures 1, 4, 7, and 10. Represents the next position.

Example 1 1:4.5. f=46.37. m=-0,11
0,ω=1g,l.

j'+=54.22. f/ft rhinoceros, o, y6f1,
2.3=81. fi5. f/f+, 2-s=0.5
7r=oo d'=3. On'=151
825 1/=6193r=”d'=4
43488〃 r'+ =25.811 da =6.304
nl =1.758441'+=52.09r -62
,02d2 =0284 r3=19.872 d3 =4.082 n
2=1.79025 shi2=49.75r4=45.
685 d4=1.026 n3-16441
9 Q=3422r5= 12f199 ds
=12.245rb ”” 11.94 d6”
0965 n4=164419 s'4"342
2r7”-133432dt =3974 n5=1
．． 758441'5=52.09r8=-16,201
ds = 0.117r, = 148.565d
9=2.604 n6=1.75844 Shiro=
52.09r,,=-32,f502 d+o=5
．． 5r7. =ωd11=300n7=151825 Schiff=6393'+2". d12=6557r,
3=0) d13=07 n5=1.
51825 Fifth surface of Vs=63.93r14=Aperture 5.204 A cross-sectional view showing the lens configuration of this example is shown in FIG.

The aberration curve diagram is shown in FIG. 2, and the transverse aberration curve diagram is shown in FIG. 3. These aberrations are at magnification m=-0,110. In the drawings, y represents the object height.

The same applies to the following examples.

Example 2 1:4.5. f=46.379m=-0110,ω
=18.1°f1=62.31. f/f+ =07
4r=cxv d”=444.448r1=2
7.989 dl = 5566 n1 = 1.79
013 W1=4393r2=59.171 d2
=0.314r3=19.103ds=4015
n2=1.79025 shi2=49.75ra”
101.558 da =1.124 n, 5=1
．． 644191'3=3422rs=12.064
ds = 12.02r6 = 12.149 d6
=0.977 n4=1.64419 W4=34
22ry = -99,286d7 = 3.683 n5
=1.75844! '5=52D9r8=-1626
1 ds -0,229r) = -116,679d
v = 3.157 n6 = 1.75844 Shiro = 5
2.09r+o=-31,486dl (1=6.5'N
=oo ci11=:3o,o
n7=1.51825 ν)=6
a93 "+2:ω d12=7.>32 '1s=" d1,5=0.7 118=1.
51825 5th surface of sig=63.93r14=~diaphragm 95.345 A cross-sectional view showing the lens configuration of this example is shown in FIG. 4, its aberration curve diagram is shown in FIG. As shown in the figure.

These aberrations are at magnification m=-0110.

Example 3 1:45. 1-4e, 37. m=-olto,
ω=179.

f+=62.16. f/f1=0.75゜r=2
5256 dl=2359 01”1.7584
4 1'+=5209r =52203 d2=0
82 r =]5.187 ds"4.066 n2
=1.69974 1'2=5627r ”177.7
34 d+=1039 113=1.58482
95=40.47r=10086ds=]1.
137r”-12834d6”0.984n
4=1.58482 '4=40.47r =85.
229 dy=3.793 n5=1.672
79 Vs=5'H)7r 16361 d*=
0.532r -147.668 dv=2.6
8 n6=1.75844 Shiro=5209
r shi43.772 d+o=65 r ”” dI+=30. o n7=1.5
1825 97=6393r=L:od12=5.
667 r=” d13=0.7 ng=1.5
1825 1'5=63.93 5th aperture 5.72
9 A cross-sectional view showing the lens configuration of this example is shown in FIG. 7, an aberration curve diagram thereof is shown in FIG. 8, and a transverse aberration curve diagram thereof is shown in FIG. 9.

These aberrations are at magnification m=-0110.

Example 4 1:4.5. f=46.37. m=-0,11
0, ω=18.2゜c=50.76, f/11=0
．． 9N.

r+ =25533 d+ =4.777 n1
=1.75844 N=52.09r2 =69.6
9 d2=0.106r5=18.218 d
3:3.992 n2=:1.84562 W2-
4299ra =2239i d4=0.987
n3=], 72734! '3=29D2rs''
11.719 ds = 1.3518r65-12
331 d6=1.064 n4=1.74706
1'a=2757r 45546d
y = 3.863 n5 = 1.8456
2 &'s =4299rs:>1538
ds=0.126rp shi440881 dv=
2.52 n6=1.75844 M6=52Ω
9r, o>39.476 d, Q=6.5rn=cD
dt1=30. Ony=1.51825 Wr=63
93rl 2 = oodl 2 = 732 r+s=a:1d15=Q, 7 n8=1.518
25 k'n = "6193r14"■ 5th surface ~ aperture #) A cross-sectional view showing the lens configuration of the example of 5.42 is shown in Fig. 10, its aberration curve diagram is shown in Fig. 11, and a lateral aberration curve diagram is shown in FIG. These aberrations are at magnification m=-0,110.

(Effects of the Invention) As is clear from the aberration curves of the above embodiments, the lens of the present invention can reduce longitudinal chromatic aberration and the entire image height even when reading a wide (12 inch m = 304°80) color original. Astigmatism is small, and chromatic aberration of magnification is also extremely small, as is clear from the coma aberration curve. Not limited to the above embodiments, but within the scope of the claims,
It was found that a high-performance lens comparable to these can be obtained. In this way, the lens of the present invention can read wide-width (12-inch) originals, and can read originals in three colors: blue, red, and green. When separated, the difference in horizontal magnification of each color is very small, 'd! It is a high-performance lens that can read with high density,
It is also easy to manufacture◎

[Brief explanation of the drawing]

Figures 1 to 3 relate to Example 1. Figure 1 is a cross-sectional view of the lens configuration, Figure 2 is an aberration curve diagram, Figure 3 is a transverse aberration curve diagram, and Figures 4 to 6 are examples of implementation. 4 is a sectional view of the lens structure, FIG. 5 is an aberration curve diagram, and FIG. 6 is a lateral aberration curve diagram. 8 is a sectional view of the lens configuration, FIG. 9 is an aberration curve diagram, FIG. 9 is a lateral aberration curve diagram, FIGS. 10 to 12 are related to Example 4, and FIG. 10 is a sectional view of the lens configuration. Fi aberration curve diagram, FIG. 12 is a lateral aberration curve diagram. Patent applicant Rico Co., Ltd. - Applicant's agent Fumi Sato, patent attorney (and 2 others) Figure 92 sine strip v1 Figure 3 Figure 11 Figure -11, 11111f1, lil -n, Hl
++ I1, lf1 ball 1wIIY difference
il: +'A IIY difference; E string η Commissioner of the Patent Office Black [11 Akio Tono 1.・! Display of 1985 Patent Application No. 219435 2, Title of invention: High-density Gauss type lens for color 3, Relationship to the person who makes corrections Patent applicant address: Tokyo Metropolitan University [1-3 Nakamagome, F1-ku, Nakamagome] Number 6 Name (674) Ricoh Co., Ltd. Representative Hama 1) Hiro 4, Agent 6, Number of inventions increased by amendment None 7, Contents of amendment 1) Amend the "Scope of Claims" as shown in the attached sheet do. 2) On page 4, lines 19 and 20 of the specification, "By providing appropriate refractive power to the first to third lenses!" was changed to "By appropriately distributing refractive power to each lens." Correct to. 3) Correct Figures 1, 2, 4, 7, and 10 as shown in the attached sheet. As claimed above, the first group facing the object consists of a first lens of a convex meniscus lens with its convex surface facing the object side, and the second group consists of a second lens of a convex meniscus lens with its convex surface facing the object side. It consists of a cemented lens of a meniscus lens with a third lens, or a cemented lens of a biconvex second lens and a biconcave third lens. The third group is a concave meniscus lens with the convex surface facing the image side.
A cemented lens of a lens and a fifth lens of a convex meniscus lens, or a fourth lens of a biconcave lens and a fifth lens of a biconvex lens.
The diaphragm is placed between the second and third groups, and the fourth group consists of the sixth lens, which is a convex meniscus lens with its convex surface facing the image side.The whole consists of four groups. 6
In a lens system in which a three-color separation prism is placed behind the fourth group, n1, n2...n v1
, ν2...ν6 are A of the first to sixth lenses, respectively.
When r1 is the refractive index and Atsube number, f is the combined focal length of the entire system, fl is the focal length of the first lens, and f 142 $3 is the focal length from the first lens to the third lens, (n□+n
a)/2>1.75. yl>43.01.86>
n2) 1.69. 57.0>ν2>42.00.9
2>f/f, >0.730.70>f/
f1. , , , >0.531.86>n, >1.
66. A color Gaussian lens characterized by satisfying the conditions of 58.0>ν and >42.0.

Claims (1)

[Claims] (1) The first group facing the object consists of a first lens of a convex meniscus lens with a convex surface facing the object side, and the second group consists of a first lens of a convex meniscus lens with a convex surface facing the object side. The third group consists of a cemented lens of two lenses and a third lens of a concave meniscus lens, or a cemented lens of a second lens of a biconvex lens and a third lens of a biconcave lens, and the third group is a concave meniscus lens with the convex surface facing the image side. The fourth lens of the lens and the fifth of the convex meniscus lens
It consists of a cemented lens with a lens, or a cemented lens with a fourth lens that is a biconcave lens and a fifth lens that is a biconvex lens, and an aperture is arranged between the second group and the third group, and the fourth group is a convex lens. In a lens consisting of the sixth lens of a convex meniscus lens with n facing toward the image side, the entire lens is composed of 6 elements in 4 groups.
_1, n_2...n_6; ν_1, ν_2...ν_6 are the refractive index and Abbe number of the first to sixth lenses, f
When is the combined focal length of the entire system, f_1 is the focal length of the first lens, and f_1_・_2_・_3 are the focal lengths from the first lens to the third lens, (1) (n_1+n_+6)/2>1.75 , ν_1>
43.0 (2) 1.69<n_2<1.86, 57.0
>ν_2>42.0(3)0.73<f/f_1<0.
92 (4) 0.53<f/f_1_・_2_・_3<0.7
0(5)1.66<n_5<1.86, 58.0>ν_
Gauss type lens for color that satisfies the condition 5>42.0. (2) A color Gaussian lens according to claim 1, characterized in that a three-color separation prism is arranged behind the fourth group.