JPH0421805A - Reading lens for scanner - Google Patents

Abstract

PURPOSE:To obtain a scanner reading lens capable of forming a bright image with a wide angle and excellent resolving power by constituting the reading lens of seven lenses in five groups obtained by successively arraying the 1st to 5th groups from the object side to the image side and arranging a stop between the 2nd group and the 3rd group and allowing the reading lens to satisfy specific conditions. CONSTITUTION:The 1st group is constituted of the 1st lens 10 to be a positive lens and the 2nd lens 12 to be a negative lens joined with the image side of the 1st lens 10, the 2nd group is constituted of the 3rd lens 14 to be a meniscus lens turning its convex face to the object side and the 3rd group is the 4th lens 16 to be a meniscus lens turning its convex face to the image side. The 4th group is constituted of the 5th lens 18 to be a negative lens and the 6th lens 20 to be a positive lens joined with the image side of the 5th lens 18 and the 5th group is the 7th lens 22 to be a parallel plate glass, i.e. a cover glass for the photodetecting face of a solid image pickup element. The stop 15 is arranged between the 3rd lens 14 and the 4th lens 16. The lens faces of the 4th to 7th lenses lenses counted from the object side are aspherical and these conical contacts K4 to K7 satisfy the condition of an expression I. Consequent ly, color division on an image face is suppressed while maintaining the flatness of a radial image face to be the original merit of a topogon type.

Description

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

[Prior art] A reduced image of a document is formed on a solid-state image sensor such as a CCD,
2. Description of the Related Art Document reading, which scans a document and reads a document image, is known in connection with image scanners, facsimile machines, digital copying machines, and the like.

A scanner reading lens is a lens for forming a reduced image of a document on a solid-state image pickup device during the above-described document reading.

Reading lenses for scanners are required to have a wide angle of view with a small object-to-image distance in order to make document reading devices more compact, and also to be large in diameter and bright in order to speed up document reading. Something is required.

Furthermore, in view of the fact that the pixel size of solid-state image sensors has become smaller in recent years, high-resolution reading lenses for scanners are also required to enable high-resolution reading that takes advantage of the capabilities of solid-state image sensors. . For example, in the case of a reading device using a CCD with a pixel size of 7 μm, the reading lens for the scanner needs a resolution of 71.4 lines/mm on the light-receiving surface of the CCD, and in addition, the above-mentioned space is High contrast with respect to frequency is required.

The 1-pogon type lens, which has been known for a long time as a lens suitable for a wide angle of view, has a flat radial image surface, and from this point of view, a topogon type scanner reading lens has been proposed (for example, Publication No. 63-75721, No. 6
4-23215).

[Problems to be Solved by the Invention] However, on the other hand, the Topobon type lens has the problem of lacking brightness, making it difficult to meet the demand for faster document reading. There is also the problem that color splitting on the image plane increases as the angle of view becomes wider, resulting in a decrease in contrast.

The present invention was made in view of the above-mentioned circumstances, and
The objective is to provide a new reading lens for scanners that is based on the Topobon type lens and has a bright FNO of 3, a wide angle of view, and excellent resolution.

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

The scanner reading lens of the present invention is a "document reading lens used with reduction magnification", and has first to fifth groups arranged sequentially from the object side to the image side, and the second and third groups.
It is composed of 7 elements in 5 groups with an aperture between the groups.

The basic structure of the lenses of claims 1 to 5 is the same.

That is, as shown in FIG. 1, the "first group" is composed of a second lens 12, which is a positive lens, and a second lens 12, which is a negative lens cemented to the image side thereof.

The "second group" is the third lens 14, which is a meniscus lens with a convex surface facing the object side. The "third group" is the fourth lens 16, which is a meniscus lens with a convex surface facing the image side.

The "fourth group" is composed of the fifth lens 18, which is a negative lens, and the sixth lens 20, which is a positive lens cemented to the image side of the fifth lens 18. The “fifth group” is the seventh group, which is a parallel plane glass.
The lens 22 is specifically a cover glass of the light-receiving surface of the solid-state image sensor.

A diaphragm 15 is provided between the third lens 14 forming the second group and the fourth lens 16 forming the third group.

Furthermore, the lenses of claims 1 to 5 have in common that in the above basic configuration, four lens surfaces are aspherical.

In the lens according to the first aspect of the present invention, the lens has a diameter of 4 degrees and 5 degrees, counting from the object side. 6th. The seventh lens surface is an aspherical surface, and the conic constant of these aspherical surfaces is 4. 5. 6. 7 is (1-I)
,,025<K,<,,005(1-II
) 0.005<K5<0
．． 015(1-III) 0.0 < K,
<0.01(1-TV),,008<
The condition K, < 0.0 is satisfied. Of course, the suffix to the conic constant is "aspherical lens surface"
For example, when the sixth lens surface from the object side is an aspherical surface, 6 represents the conic constant of this aspherical surface.

In the lens according to the second aspect of the present invention, the angle is 4° and 5° as counted from the object side. 6th. The eighth lens surface is an aspherical surface, and the conic constant of these aspherical surfaces is 4. KS, 6. 8 is (2-I)
,,03< , < ,,01(
2-II) 0.008 < K5 < 0.02
5(2-III) 0.01 <K, <
0.025(2-IV), ,6<K,<
The lens according to claim 3, characterized by the conditions L and S, has a 4th degree, a 5th degree, and a 5th degree, counting from the object side. 6th. The tenth lens surface is an aspherical surface, and the conic constants of these aspherical surfaces are +tK and 6tK+o, (3-I
) ,,025<K4< ,,007(3-II)
0.008 < K5 < 0.02 (3-II
I) 0.008 < K, < 0.02
8(3-IV) 0.005 < KI
The lens according to claim 4, which is characterized by the condition O<0.015, has an angle of 4° and a 5th angle as counted from the object side. 7th. The eighth lens surface is an aspherical surface, and the conic constant of these aspherical surfaces is 4. 5. 7. K11 is (4-I)
,,03<K4<,,01(4-II)
0.005 < Kg < 0.025 (4(T
I). 03 く に 7〈 ゜01(４
-IV) 0.45 < K 8
The lens according to claim 5, which is characterized by the condition of < 7.0, has an angle of 4° and 6.0° as counted from the object side. 7th. The tenth lens surface is an aspherical surface, and the conic constants K4 and Ks+ of these aspherical surfaces are 7. +o is (5-1
) ,,045<K4< ,,015(5(I
) 0.0 < K6 < 0.013 (5
-III) , ,023<Kt'< ,,005
(5-hari 0.0<KIO<
The condition of 0.02 is satisfied.

In this way, the lenses of claims 1 to 5 have in common that the fourth lens surface is an aspherical surface.

Furthermore, the lenses according to claims 1 to 4 have in common that the fifth lens surface is an aspherical surface.

Furthermore, the lenses according to claims 1, 2, 3, and 5 commonly employ an aspherical surface as the sixth lens surface.

As is well known, for an aspheric surface, X is the direction of the optical axis, H is the height perpendicular to the optical axis, and C is the reciprocal of the radius of curvature on the optical axis.
When, the curve
-H2+A3-H3+A4H'・---+A10-H1
It is a curved surface obtained by rotating 0+-. around the optical axis, and the conic constant is K in the above formula. Further, in the above equation, AQrA3t-, etc. are high-order aspherical coefficients.

[Function] The lenses according to claims 1 to 5 are all based on a tobogon type in order to achieve a wide angle of view. Although the Topobon type lens has a flat radial image surface with little curvature, the color breakage on the image surface increases as the angle of view becomes wider, reducing contrast.

In order to solve this problem of decreased contrast due to color cracking, the first group and the fourth group are made of a combination of positive and negative lenses. By doing this, it was possible to maintain the flatness of the radial image plane, which is an inherent advantage of the tobogon type, and to suppress color breakup on the image plane.

Additionally, in order to achieve a larger aperture, four lens surfaces are aspheric.

Generally, the larger the aperture, the more coma flare and the lower the contrast. In order to suppress coma flare, it is best to correct the extremely refracted surface among the input and exit surfaces.

However, with a spherical surface, the same correction cannot be made on any of the entrance and exit surfaces, so it is insufficient for correcting coma flare.

Therefore, an aspheric surface is used as a means to continuously change the refractive power from the axis toward the periphery.

This makes it possible to suppress coma flare at large apertures.

Like the lens of claim 1, the fourth. Fifth. 6th degree: When using an aspherical surface for the 7th lens surface, condition (1-I)
The aspherical shape of the fourth lens surface that satisfies the condition (1-II) is "an ellipsoidal surface that is rotationally symmetrical about the major axis," and the aspherical shape of the fifth lens surface that satisfies condition (1-II) is "an ellipsoidal surface that is rotationally symmetrical about the minor axis."",conditions(
, 1-III) is an ellipsoid that is rotationally symmetrical about the minor axis, and the aspherical shape of the 7th lens surface that satisfies the condition (1-m is an ellipsoid that is rotationally symmetrical about the major axis). It is a symmetrical ellipsoid, and the conditions (1-I), (1-IIL (1-
III) When satisfying (1-IV), the smallest coma flare can be achieved.

Like the lens of claim 2, the fourth. Fifth. 6th degree When adopting an aspherical surface for the 8th lens surface, condition (2-I)
The aspherical shape of the fourth lens surface that satisfies the condition ``r'' is an ellipsoidal surface that is rotationally symmetrical about the major axis, and the aspherical shape of the fifth lens surface that satisfies the condition (2-II) is ``an ellipsoidal surface that is rotationally symmetrical about the minor axis.''",conditions(
The aspherical shape of the sixth lens surface that satisfies 2-III) is “
The aspherical shape of the 8th lens surface that satisfies the condition (2-IV) is "an ellipsoidal surface rotationally symmetrical about the major axis or the minor axis," and the condition (2-I) , (2-
When satisfying II), (2-III), and (2-IV), the smallest coma flare can be achieved.

Like the lens of claim 3, the fourth. Fifth. 6th゜10th
When adopting an aspherical surface for the th lens surface, the condition (3-I
), the aspherical shape of the fourth lens surface is an ellipsoidal surface that is rotationally symmetrical about the r major axis, and the aspherical shape of the fifth lens surface that satisfies condition (3-II) is an ellipsoidal surface that is rotationally symmetrical about the minor axis. The aspherical shape of the 6th lens surface that satisfies condition (3-III) is "an ellipsoidal surface rotationally symmetrical about the minor axis", and the aspherical shape of the 1st O lens surface that satisfies condition (3-IV) is "It is an ellipsoid surface that is rotationally symmetrical about the short axis", and the conditions (3-I), (3-II),
(3-III), (It is possible to achieve the smallest coma flare that satisfies 3-m.

Like the lens of claim 4, the fourth. Fifth. 7゜When adopting an aspheric surface for the 8th lens surface, condition (4-I)
The aspherical shape of the fourth lens surface that satisfies the condition (r) is "an ellipsoidal surface that is rotationally symmetrical about the major axis", and the aspherical shape of the fifth lens surface that satisfies condition (4-II) is "an ellipsoidal surface that is rotationally symmetrical about the minor axis". ",conditions(
The aspherical shape of the seventh lens surface that satisfies 4-III) is “
The aspherical shape of the eighth lens surface that satisfies the condition (4-IV) is "an ellipsoidal surface rotationally symmetrical about the major axis" and the condition (4-I), (4 -II),
The smallest coma flare can be achieved when (4-III) and (4-IV) are satisfied.

Like the lens of claim 5, the fourth. 6th. 7th゜10th
When adopting an aspherical surface for the th lens surface, the condition (5-I
), the aspherical shape of the fourth lens surface is an ellipsoidal surface that is rotationally symmetrical about the r major axis, and the aspherical shape of the sixth lens surface that satisfies condition (5-II) is an ellipsoidal surface that is rotationally symmetrical about the minor axis. The aspherical shape of the seventh lens surface that satisfies condition (5-III) is "an ellipsoidal surface that is rotationally symmetrical about the long axis," and the aspherical shape of the first O lens surface that satisfies condition (5-m) is " It is an ellipsoidal surface that is rotationally symmetrical about its minor axis, and the conditions (5-I), (5-II), (
5-III) and (5-IV), the smallest coma flare can be achieved.

[Examples] Below, three specific examples will be given for each lens in each claim.

That is, Examples 1 to 3 are examples of the lens according to claim 1,
Three embodiments of lenses according to claims 2 to 5 are successively described below.

In each example, the first lens is a positive meniscus lens, the second lens is a negative meniscus lens, the third lens is a negative meniscus lens, the fourth lens is a negative meniscus lens,
The fifth lens is a biconcave lens, and the sixth lens is a biconvex lens.

In each example, the radius of curvature of the first lens surface from the object side (on-axis radius of curvature for an aspherical surface) is r, (i=1 to 12), j-th lens surface as shown in FIG. Let di (i = 1 to 11) be the distance between the surfaces of the th lens, and let the refractive index and Atsube number of the j th lens be na t V i (j = 1
~7).

Further, F indicates the combined focal length of the entire system, FNO indicates brightness, 2ω indicates the angle of view (degrees), and m indicates magnification.

Aspherical surfaces are marked with *, and outside the axial radius of curvature, the conic constant and higher-order aspherical coefficients A41A6? Specify the aspherical shape by giving Al11A10.

In the display of the aspheric coefficient, E and the number following it indicate a power of 10. For example, E-12 means 10.12, and the number before E is multiplied by this power.

Example 1 F-43, FNo=3.0.2ω i ri d.

1 19.314 7.2192 103
．． 154 2.4863 37.877 0
．． 1004* 15.167 2.6315”
10.683 9.6006″ -9,2
392,075 7' -12,2740.230 8-1010372,487 9172,0385,756 10-20.31721556 11ω 0.700 12o.

Aspherical surface (fourth lens surface) K=,,007726,A,=-5,87063E-7
,A6=3.47374E-9Aa=-2,8363
7E-10. Axo=-1,09280E 11 Aspherical surface (5th lens surface) K” 0.006210.A4= 1.98334E
6. A6" 1.86891E 8A, = -1,558
02E-9,A,,=-1,28865E-1023,
89 1,84666 46,62 23,89 23,89 64,15 1,51633 1,84666 1,81600 1,84666 , m=0.1102 nj 乍 j 1.81600 46.62 1.84666 23.89 Non Spherical surface (sixth lens surface) K=, 0.002712. A, = -5,35655E
-6,A6=-3,23488E-8゜A,=-1,9
8934E-9, A10 = 2.92978E-11 Aspherical surface (7th lens surface) K =, 004544, A4 = 2.86203E-6
, A6=-2, 61408E-8A8=4.6811.
9E-10. A. = 4.44187E-12 Example 2 F=43, FNO"3.0.2 (+3"40
, m=0.1102i ri ds
J nj νj1 18.619 6
．． 378 1 1.72916 54.682 9
2.194 2.587 2 1.78472 25
．． 713 41.176 0.100 4” 15.248 3.165 3 1.84
666 23.895" 10.660 9.72
2 6” -8,9692,70041,740772
7,797" -12,3690.100 8-116,7071,00051,6889331,
08975,0255,61161,7291654,
6810-19,83627,719 11■ 0.700 7 1.51633 64.
15 Aspherical surface (4th lens surface) K”, 007939, A4-5.75868E-7,
A6= 1.83337E-9゜As=-2,3497
3E-10. A to”-9,47713E-12 Aspherical surface (fifth lens surface) K=0.007616.A4=2.51877E 6
．． A6=2.07403E-8゜Aa=-1,8372
1E-9, Ato”-1,43638E 10 Aspherical surface (
6th lens surface) K” 0.001956.A4”-6,24888E-
6, As”-5,29165E-8゜Aa”-2,37
821E-9, A+o=4.09913E-1,1 aspherical surface (7th lens surface) K=,,001970. A4=2.62106E-6
,A,=-3j3922E-8°A8=4.1911
5E-10. As. = 5.36160E-12 Example 3 F”43, FNO”3.0.2ω”40
, 'm"o, 1102i r, d,
j nj 'IIJ1 19.299
6.821 1 1.81600 46.602
133.300 2.114 2 1.78415
25.743 38.743 0.100 4” 16.886 3.029 3 1.84
700 23.905”, 11.258 9.
7596" -9,9772,12541,84
70023,9075-13,6290°100 8 -90.579 2.272 5 1
．． 79482 25.399 101.701
5.526 6 1.82529 44.5810
-20.078 28.09811 ω
0.700 7 1.51633 64.
1512 ω Aspherical surface (fourth lens surface) K= 0.020911. A4 knee 1.44304E
-6,A6=5.86942E-9A8=-1,7
2683E-1,0. A. =-7,70834E-1
2 Aspherical surface (fifth lens surface) K=0.014573. A4=3.14357E-6
, As= 5.57660E-8°A8=-6,520
62E-11,A,,=-1,32039E-10 aspherical surface (sixth lens surface) K=0.007834. A, =-7,05967E-
6, A6=-6,44336E-8゜Aa=-2,84
513E-9, Ago” 5.52465E-11 Aspherical surface (7th lens surface) K”, 007183, As” 3.50868E 6
．． A,,=-3,94955E-8°As=6.699
31E 10. AI(+" 4.70215E-12 or more is an embodiment of the lens of claim 1.

FIG. 2, FIG. 3, and FIG. 4 show aberration diagrams of Examples 1 to 3, respectively.

In addition to the aberration diagrams in Figs. 2 to 4, in the aberration diagrams of each example below, ■, ■, and ■ represent the d-line and C-line, respectively.
Indicates that it is related to the F line.

Further, the broken line in the diagram of spherical aberration indicates the sine condition, the solid line in the diagram of astigmatism indicates the radial condition, and the broken line indicates the tangential condition.

Example 4 F: 43, FNo=3.0.2ω: 40
, m=0.11.02j, r i d
1J n jl 19.242 7.307
1 1.81600 46.622 101.82
0 2.578 2 1.84666 23.893
38.021 0.100 4" ], 5.065 2.599 3 ],,
84666 23.895” 10.543 9.
716 6”-9,4682,1544], 84666
23.897 -12.743 0.226 8" -98,8252,50751,846662
3,899181,7675,78361,81600
46,6210-20.03827,4,97 11■ 0.700 7 1.51633 64.
1.512ol) Aspherical surface (4th lens surface) K=, 010743, A4=-8-59455E-7
,A6=3.55753E-9AB=-2,7574
8E-1,0. Ato"-1,04797E-11 Aspherical surface (fifth lens surface) K = 0.009127.A, = 2.54483E-
6, A6=3. '60859E-8Aa"-1,10
441, E-9, AI. =-1,,30207E-1,
0 aspherical surface (sixth lens surface) K = 0.011.377, A, = -1,12257E
-5,A6=-1,84809E-8As"-1,83
061E-9, Al0 = 5.27510E-12 Aspherical surface (8th lens surface) K =, , 546906, A4 = 9.27186E-8
,A,=-5,22065E-9A,=-8,1358
2E-11,A. = 5.04686E-13 Example 5 F=43, FN, =3.0.2ω=40 2
m=0.1102i rId+ , 11
nj νj1 18.502 6.421
1 1.72916 54.682 90.611
2.676 2 1.78472 25.713
42.794 0.100 4” 15.541 3.352 3 1.84
666 23.895* 1 (L536 9.88
7 6” -9,5252,99041,740772
7,797-13,6200.100 8 years old -11L221 1.000 5 1.688
93 31.089 7L319 5.961 6
1.72916 54.6810 -19.142
27.039 11 co O,7007],,51
633 64. ], 512 ω Aspherical surface (fourth lens surface) K=, ,013769, A4=-9,76355E-7
, As=-1,66869E-9°AB=-]-,]9
5469E-10. Axo=-743859E 12 Aspherical surface (fifth lens surface) K=0.015481. A, = 3.95835E-
6, A6 = 5.40943E-8A8”-7,195
58E-10. A10 = 1.44811E-10 aspherical surface (sixth lens surface) K = 0.018872. A4=-1,69825E-
5, A6=-8,00455E-9Aa"-2,344
20E-9, Aio = 4.08460E-1,2 aspherical surface (8th lens surface) K = 1.520847. A4=-1,,37627E
-7,A,=-1,,00174E-8°A11=1.
13045E-10. A10=6.50759E-1
, 3 Example 6 F=43, FNO"3.0.2ω=40
,m,,1102i rl dl
j nj νJ1 19.130 6.90
4 1 1.81600 46.602 124.
557 2.178 2 1.78365 25.7
63 38.802 0.100 4” 16.436 2.929 3 1
．． 84700 23.905t 10.861 1
0.0786" -10.7092,27541,
8470023,907-1,5,0170.1,00 8"-84,1372,15251,77528
26,059102,8905,46] 6
1.82481 44.6910 -19.493
27.87311 ω 0.700
7 1.51633 64.1512 ω Aspherical surface (fourth lens surface) K”, 027107, A4”-1,85755E-6
,A6” 3.99999E-9As”-1,2518
3E-10. A10"-6, 20598E-12 Aspherical surface (fifth lens surface) K: 0.021729.A<" 4.35814E-6
, A6= 8.26410E-8Aa= 9.3361
7E-10. A, 0=-1,07205E-10 aspherical surface (sixth lens surface) K=0.022612. A4”-1,48818E-
5, As=-i, o1796E 8Aa”(,8243
0E-9, Ato” 2.17492E-11 aspherical surface (
8th lens surface) K=0.705187. A, =-1,25758E-
7,A,=-1,19374E-8°A8=-1,54
368E-10. A1o=9.51044E-13 or more is an embodiment of the lens according to claim 2.

Aberration diagrams of Examples 4 to 6 are shown in FIGS. 5, 6, and 7, respectively.

Example 7 F=43, FNO"3.0.2ω"40, m=o, 11
021 rl dt j
njl 1L376 7.194
1 1.81600 46.622 103.83
9 2.585 2 1.84666 23.8
93 39.876 0.100 4″15.876 2.891 3 1.846
66 23.895*10.793 9.728 6” -10.0182,35741,84666
23,897-13,8360.100 8-102,8312,68651,8466623,
899185,5535,8756' 1.81600
46.6210* -19,76427,195 11C,) ' 0.700 7 1.516
33 64.1512 ω Aspherical surface (fourth lens surface) K”, 015289, A4=-1,09285E-6
,A6"3.50841E-9As"-3,6597
8E-10. Axo=-7, 19566E-12 Aspherical surface (fifth lens surface) K” 0.012935.A4= 3.43578E-
6, As” 1.91338E 8Aa=-5,675
13E-10. A10=-1,34023E-10 Aspherical surface (6th lens surface) K” 0.024903.A4”-1,61961E
5. As” 1.18316E-7Aa=-4,440
27E-9, Ato” 3.42147E-11 Aspherical surface (10th lens surface) K= 0.013667, A4=-2,24994E-
8, A6=-8,49582E-9Aa” 6.041
21E 11. AIO” 4.83092E-14 Example 8 F=43, FNo=3.0.2ω=40
, m=o, 11021rs dt j
nj'l' jl 18.604 6.451
1 1.72916 54.682 91.293
2.655 2 1.78472 25. '713
41.290 (1,100 4' 15.066 3.211 3 1.84
666 23.895' 10-520 9.73
6 6' -9,1102,73841,740772
7,797-12,5930.100 8-108-3301, 12151, 6889331,
08976,0555,73061,7291654,
6810* -19,56127,146 11oo O,70071,5163364,
15 Aspherical surface (4th lens surface) K=,,008222,A,=-6,14911E-7
, A6= 1.44423E-9Aa"-2,6130
7E-10. A10=-9,32834E-12 aspherical surface (fifth lens surface) K=0.008685. A4=2.87301E-
6, A5 = 2.16682E-8°An”-1,84
966E-9, A10"-1, 43327E-10 aspherical surface (sixth lens surface) K = 0.009162.A, = -1,15166E-
5, A6=-7,09157E-8゜Aa=-3,20
794E 9, Axo" 1.32359E-11 Aspherical surface (10th lens surface) K = 0.006066, A, = 3.50254E-
8, A6=-5, 18650E-9°A, = 3.81
169E-11, A1. = '191913E-14 Example 9 F=43, FNO=3.0.2ω=40.1T
l=0.1102j rl d
l j Jl, 1.9
．． 24.2 6.892 1 1.81600
46.602 126.440 2.160
2 1.78503 25.713 38
．． 850 0. ．． 1004' Coro, 387
2.947 3 1.84700 2
3.905" 10.899 9.9506"
-10.6692,21341,8470023
,907-14,8710.100 8-80.8842,28851,7761826,0
29101, 1125, 53061, 8255444,
5310"-19,49628,02211ω
0.700 7 1.51633 64.
1512 ω Aspherical surface (fourth lens surface)=,,022627,A4=-1,5742]E~5
．． 80 = 2.69133E-9゜Aa”-2,232
43E-10. A+o=-5,31,495E-12 aspherical surface (fifth lens surface) K=0.019459. A, = 4.23178E-
6, A, = 5.14032E-8Aa"3.6'5
686E-10. Ato”-1,03], 06E-],
0 Aspherical surface (6th lens surface) K"0.025962.A4" 1.51056E-
5, As=-8,64870E-8°A,=-3,46
569E-9, A,, = 4.4135/! , E-11
Aspherical surface (10th lens surface) K"0.00B445.A4" 1.70139E-
7, As”-7,80014E-9゜Aa” 7.07
135E-11, Ato'' 5.77403E-14 and above are examples of the lens of claim 3.

Aberration diagrams of Examples 7 to 9 are shown in FIGS. 8, 9, and 10, respectively.

Example 10 F=43, FNO=3.0.2c, +=40
,m,,1],2i rid,
j nj νj1 1.9.281 7
．． 297 1 1.81600 46.622 1
02.169 2.574 2 1.84666 2
3.893 38.222 0.100 4” 15.106 2.597 3 1.84
666 23.895” 10.566 9.77
9 6 -9.399 2. ], 47 4 1. ．． 84
666 23.897'4-12.602 0.171 8 heat -103,8572,47051,846662
3,899175,1,215,75161,8160
046,6210-20.1,7527,364 11oo O,70071,,516336C1
512ω Aspherical surface (fourth lens surface) K", 011192, A4"-8, 66808E-7
,As” 2.07607E-9A,=-2,7140
4E-]]0. A,,=-1. ．． 00750E11 Aspherical surface (fifth lens surface) K= 0.009634. A, = 2.59438E-
6, A, = 3.98705E-8A, = -1,001
60E-9, A,, = -1,, 26687E-10 Aspherical surface (7th lens surface) K knee 0.014781. A,” 6.26553E-
6, As=-2,25558E-8A,=2.786
78E-10. A,, = -4,19079E-13 Aspherical surface (8th lens surface) K = 0.498259. A4=-8,59327E-
8, A6=-7,89338E-9A8=-7,977
84E-1,1, A10=7.10197E-13 Example 11 F”43, FNO”3.0.2ω=40
, ln=0.1102i rl dl
j njl 18.487 6.420
1 1.729] 6 54.682 90.200
2.853 2 1.78472 25.713
42.385 0.1004” 15.
392 3.274 3], 84666
23.895o 1.0.513 9.9846
-9.301 2.915 4
],,74077 27.797" -13,19
10.100 8” -135,1641,00051,68893
3LO8974,3685,87361,,72916
54,6810-19,56927,057 11ω 0.700 7 1.51633
64.15]2oO Aspherical surface (4th lens surface) K knee 0.012804. A4”-8, 28869E-
7, A6=-5,38829E-9゜Aa=2.220
47E-1,0. Ato”-7,34697E-12 Aspherical surface (fifth lens surface) K” 0.015313=A4” 3.94826E-
6, Aa” 4.62752E 8゜Aa”-9,72
4,87E-10. Ato”-1,36036E-10
Aspherical surface (7th lens surface) K”, 018923, A+= 7.48240E 6
．． A6”-3,971,75E-8゜Aa=2.233
64EIO, Ato” 2.66167E-13 Aspherical surface (8th lens surface) = 6.753841.A4=-5,81053E-
7, A6=-1,34737E-8°A8=-9-26
288E-11,A,, = 7.74637E-13 Example 12 F"43, FNO"3.0.2ω"401rl
chi j 1 ], 9.126 6.981 12 12
:1085 2.253 23 38.501 0
．． 100 4" 16.270 2.825 5" 10.850 10.082 6 -10.309 2.235 7" -14,2690.100 8 years old -91,8902,143 999,3465,448 10-19, 87727,792 11ω 0.700 12ω Aspherical surface (fourth lens surface) K=, ,026610.A,=-1,78191E-6
,A6=1.89954E-9°A,=-1,348
25E-10. A, knee 6.74510E-1225
,88 1,78024 23,90 23,90 64,15 44,88 , m=0.1102 j 1.81600 46.60 1.78840 25.60 1.84700 1.84700 1.82388 1.51633 Aspheric surface (Fifth lens surface) K=0.020905. A4=4.17685E-
6, A6 = 8.15766E-8A, = 6.671
19E-10. A,,=-1,07437E-10 Aspherical surface (7th lens surface) K",,026440.A,=7.58012E-6
, As=-2,98413E-8°A,=2.656
31E-10. A,, = -3,16759E-12 aspherical surface (8th lens surface) K = 2.166644. A4=-3,45118E-
7, A6=-1,45940E-8°A,=-1,34
537E-10. A, , = 1.01675E-12 or more is an embodiment of the lens according to claim 4.

Examples 10 to 10 are shown in FIG. 11, FIG. 12, and FIG. 13, respectively.
12 is shown.

Example 13 F=43. FNo: 3.0.2ω=402m=0.11
021 r+ dt j nj
S' jl 19.252 7.200 1 1
．． 81600 46.622 1'08.602 2
．． 419 2 1.84666 23.893 3
7.024 0.100 4” 13.829 2.414 3 1.84
666 23.895 9.889 10.165 6' -9,8022,21941,84666
23,897″' -13,1540.140 8-90.0012,38051,8466623,8
99227, 6315, 68761, 8160046,
6210' -19,94127,332110o
O, 70071, 5163364, 1512ω Aspherical surface (fourth lens surface) K=, , 015536, A4=1-61682E 6.
Ae=8.78329E-10Aa" 3.8547
6E-11, Axo”-2, 50372E-12 Aspherical surface (sixth lens surface) K” 0.002372. A4=-6,46223E
6. A6”-1,40670E-8A, =-1,886
13E-9, A,, = 3.38447E-11 Aspherical surface (7th lens surface) K =, 006902, A4 = 3.48826E-6
, A6=-1,09248E-8A8" 4.2485
3E-10. A10”-2,35415E 12 Aspherical surface (10th lens surface) K= 0.004033.A, =-9,02074E-
8, A6=-1,98190E-9A8=2.69
633E-11, A, O2 7.33924E-14 Example 14 F=43, FNO"3.0.2ω"40
2m”0.11021ri dt
j njV jl 18.175 6.
270 1 1.72916 54.682
91.976 2.312 2 1.78472
25.713 41.307 0.1004
*13.433 2.966 3 1.8466
6 23.895 9.432 10.302 6” -10.5873, 33541, 74077
27,797" -15,6300.100 8-109,8271,00051,6889331,
08991, 3316, 08461, 7291654,
6810″′ -18,94927,143110+)
0.700 7 1.51633 64.1512
ω Aspherical surface (fourth lens surface) K=,,021817,A4=-1,96800E-6
, A6=-2,02787E-8°As” 6.333
75E-11, A10”-2,86803E 12 Aspherical surface (6th lens surface) K= 0.011509.A, =-1,63707E
-5,A62 1.75319E-8゜A8=-3,5
3031E-9, A,, = 6.65936E-11 Aspherical surface (7th lens surface) K=,,021156,A-” 6.44166E 6
．． As=-3,27972E-8゜As” 6.204
31E (0.A+o”-2,33388E-12 Aspherical surface (10th lens surface) K= 0.018740.A, =-1,07168E-
6, A6=-8,26005E-10Aa" 9.09
703E-11, A+. = 3.38409E-14 Example 15 F=43, FNO=3.0.2ω=40
, m=0.11.02i rlds j
J], 19.288 7.020 1 1
．． 81600 46.602 117.843 2.
163 2 1.80362 25.113 38
．． 343 0.100 4” 14.502 2.579 3 1.84
700 23.905 10.034 10.227 6” (1,5512,50441,8470023
,907" -16,5160.100 8-82,7981,7255L,76707 26°359 93.866 5.432 6 1.82
675 44.2910″'-19-60028,24
6 11ω 0j00 7 1.51633 64.1
512c11) Aspherical surface (fourth lens surface) K=,,042297,A,=-3,54239E-6
,A,=-2,12356E-8°A8=2.801
64E-1,1,A,,=-2,00991E-12 Aspherical surface (sixth lens surface) K=O,0t0861. A4 knee 9.48552E
-6,A,=-1,72377E-10Aa”-2,3
8836E-9, A+o” 5.40584E-11 Aspherical surface (7th lens surface) K”, 020899, C” 5.01.315E-6
, As=-2,47058E-8゜〇2 5.404
74E-10. A. =-5,60927E-12 aspherical surface (10th lens surface) K= 0.011882. A,=-3,20248E-
7,A,=-5,11423E-9゜Aa=6.95
399E-11,A, , = 2.53000E-13 or more is an embodiment of the lens according to claim 5.

Examples 13 to 14 are shown in FIG. 14, FIG. 15, and FIG. 16, respectively.
15 is shown.

Aberrations are well corrected in each example.

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

Since this lens is constructed as described above, the half angle of view is 2
It has a wide viewing angle of 0 degrees, has sufficiently high contrast even at high spatial frequencies of 71.4 lines/mm, and has a brightness of F.
It is bright as NO"3 and has a sufficiently high aperture efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the structure of the lens of the present invention, and FIGS. 2 to 16 are aberration diagrams regarding each example. 10., first lens, 12. ,, second lens, 14.
,, third lens, 15. ,,Aperture,16. , 4th lens, 18. ,, 2nd figure (realistic, 11) F/No, 5 Y-452,4 (52,4 frames, aberration 2nd figure (practice 12) spherical aberration astigmatism 11 days η ``Mu2 rock! (2) Comatic aberration Figure 4 (Implemented row A b F/No, 5 Y=P) 2.4 Y=4ri 24 Comatic aberration Figure 5 (Implemented row A 4) F/No, 3 ] Y-152,4 Ti surface My difference astigmatism distortion aberration (% Lacoma aberration Fig. 6 (Real color example) Coma aberration Fig. 7 (Real) 51 de!1 Iku・1 (S) ) 1,000-square engraving Ma difference Astigmatism Distortion aberration (%) Coma aberration 忤a figure (Actual gun example 7) Coma aberration 9 figure (Futh 4th edition Ita 16) F/No, 5 Y= (52, 4 Y=I52.4 Difference for spherical aberration, astigmatism, distortion (%) No. Distortion and white aberration (%) Comatic aberration Figure 12 (actual power) (4 diagrams on the Licoma aberration side (2) F/No. (52, 4) Spherical aberration Astigmatism Distortion (phantom coma Side 14 view (Real image 11 (U); Comatic aberration 1 (U) Figure (Real image 114) F/14o, 3 Y-1!152.4 Sphere i Aberration Astigmatism 1 ≧ Mouth B Hamon blade Day C% Nocoma aberration (0 figure (Actual value 1 5) F/No Y=(52,4 Y= 152.4 Core aberration difference

Claims (1)

[Claims] 1. A document reading lens used at a reduction magnification, in which first to fifth groups are arranged sequentially from the object side to the image side, and the second group and the third group are arranged sequentially from the object side to the image side. A diaphragm is arranged between them, and the first group is composed of a first lens that is a positive lens and a second lens that is a negative lens that is cemented to the image side of this first lens. is a third lens that is a meniscus lens with a convex surface facing the object side, the third group is a fourth lens that is a meniscus lens with a convex surface facing the image side, and the fourth group is a negative lens The fifth lens is composed of a fifth lens and a sixth lens which is a positive lens cemented to the image side of the fifth lens. 4. The fifth, sixth, and seventh lens surfaces are aspherical, and the conic constant K_4 of these aspherical surfaces is
K_5, K_6, K_7 are (1-I)-0.025
<K_4<-0.005 (1-II) 0.005<K_5
<0.015(1-III)0.0<K_6<0.01 (1-IV)-0.008<K_7<0.0 Reading lens for scanner. 2. A document reading lens used at reduced magnification, in which the first to fifth groups are arranged sequentially from the object side to the image side, and an aperture is arranged between the second and third groups. The first group includes a first lens that is a positive lens and a second lens that is a negative lens that is cemented to the image side of the first lens, and the second group has a convex surface on the object side. The third lens is a meniscus lens with a convex surface facing the image side, and the fourth lens is a meniscus lens with a convex surface facing the image side. A sixth lens is a positive lens cemented to the image side of the fifth lens, and the fifth lens is a seventh lens that is a parallel plane glass. 6. The eighth lens surface is an aspherical surface, and the conic constant K_4 of these aspherical surfaces is
K_5, K_6, K_8 are (2-I)-0.03<
K_4<-0.01 (2-II) 0.008<K_5<0
．． 025 (2-III) 0.01<K_6<0.025 (2-IV) -0.6<K_8<1.6 A scanner reader with 7 elements in 5 groups, characterized by satisfying the following condition. lens. 3. A document reading lens used at reduced magnification, in which the first to fifth groups are arranged sequentially from the object side to the image side, and an aperture is arranged between the second and third groups. The first group includes a first lens that is a positive lens and a second lens that is a negative lens that is cemented to the image side of the first lens, and the second group has a convex surface on the object side. The third lens is a meniscus lens with a convex surface facing the image side, and the fourth lens is a meniscus lens with a convex surface facing the image side. A sixth lens is a positive lens cemented to the image side of the fifth lens, and the fifth lens is a seventh lens that is a parallel plane glass. 6. The tenth lens surface is an aspherical surface, and the conic constant K_4 of these aspherical surfaces is
, K_5, K_6, K_1_0 are (3-I)-0.0
25<K_4<-0.007 (3-II) 0.008<K
_5<0.02 (3-III) 0.008<K_6<0.028 (3-IV
)0.005<K_1_0<0.015. 4. A document reading lens used at reduced magnification, in which the first to fifth groups are arranged sequentially from the object side to the image side, and an aperture is arranged between the second and third groups. The first group includes a first lens that is a positive lens and a second lens that is a negative lens that is cemented to the image side of the first lens, and the second group has a convex surface on the object side. The third lens is a meniscus lens with a convex surface facing the image side, and the fourth lens is a meniscus lens with a convex surface facing the image side. A sixth lens is a positive lens cemented to the image side of the fifth lens, and the fifth lens is a seventh lens that is a parallel plane glass. 7. The eighth lens surface is an aspherical surface, and the conic constant K_4 of these aspherical surfaces is
K_5, K_7, K_8 are (4-I)-0.03<
K_4<-0.01 (4-II) 0.005<K_5<0
．． 025(4-III)-0.03<K_7<-0.01
(4-IV) A reading lens for a scanner having a configuration of 7 elements in 5 groups, which satisfies the following condition: 0.45<K_8<7.0. 5. A document reading lens used at reduced magnification, in which the first to fifth groups are arranged sequentially from the object side to the image side, and an aperture is arranged between the second and third groups. The first group includes a first lens that is a positive lens and a second lens that is a negative lens that is cemented to the image side of the first lens, and the second group has a convex surface on the object side. The third lens is a meniscus lens with a convex surface facing the image side, and the fourth lens is a meniscus lens with a convex surface facing the image side. A sixth lens is a positive lens cemented to the image side of the fifth lens, and the fifth lens is a seventh lens that is a parallel plane glass. 7. The 10th lens surface is an aspherical surface, and the conic constant K_4 of these aspherical surfaces is
, K_6, K_7, K_1_0 are (5-I)-0.
045<K_4<-0.015 (5-II) 0.0<K_
6<0.013 (5-III)-0.023<K_7<-0.005(5
-IV) 0.0<K_1_0<0.02 A scanner reading lens having a configuration of 7 elements in 5 groups, which satisfies the following condition.