United States Patent
`Wakimoto et al.
`
`115
`
`[11] Patent Number:
`
`[45] Date of Patent:
`
`4,929,066
`May 29, 1990
`
`[54] TELECENTRIC IMAGE-FORMING OPTICAL
`SYSTEM FOR LARGE IMAGESIZE
`
`[75]
`
`Inventors: Zenji Wakimoto; Takahisa Hayashi,
`both of Kyoto, Japan
`
`(73] Assignee: Dainippon Screen Mfg. Co., Ltd.,
`Japan
`
`[21] Appl. No.: 219,552
`
`[22] Filed:
`
`Jul. 14, 1988
`
`[30]
`
`Foreign Application Priority Data
`
`Jul. 14, 1987 [JP]
`Japan cssccsssssesssesssessssseeeeeees 62-176808
`[51]
`Tmt. CRS oeececceseseeseeneeee G02B 13/22; G02B 9/64
`(50 US Cscicccccccamntncs 350/415; 350/463
`
`(58] Field of Search .................. 350/415, 6.8, 6.7, 463
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,300,817 11/1981 Betensky oo...350/412
`4,588,265
`5/1986 Takahashi «00.00...SIO/415
`
`Primary Examiner—Scott J. Sugarman
`Attorney, Agent, or Firm—Ostrolenk, Faber, Gerb &
`Soffen
`
`[57]
`ABSTRACT
`A telecentric image-forming optical system comprising
`a first lens group including a double-convex lens, a
`meniscus lens whose convex side faces an object or a
`plano-convex lens, and a double-concavelens arranged
`in this order; and a secondlens group including a dou-
`ble-convex lens, a meniscus lens whose convex side
`faces an image or a plano-convex lens, and a double-
`concave lens arranged in this order, wherein the sec-
`ondary focal pointofthe first lens group and the princi-
`pal focal point of the second lens group substantially
`coincide with each otherin the vicinity of a double-con-
`vex lens. The telecentric image-forming optical system
`is compact and forms an image whichis large sized in
`relation to the compact length of the system.
`
`15 Claims, 15 Drawing Sheets
`
`
`
`Align 2015
`3Shape A/S v. Align
`IPR2019-00150
`
`Align 2015
`3Shape A/S v. Align
`IPR2019-00150
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet1of15
`
`4,929,066
`
`Fig. 1
`
`
`
`hh tTmn oa ns he
`
`
`
`
`
` NA 0.055
`
`
`
`
`caiman C-line
`—-—— F-line
`
`eee SPHERICAL ABERRATION 272°
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet20f15
`
`4,929,066
`
`Fig. 3
` -0.1
`
`:
`SPHERICAL ABERRATION
`
`0.1
`
`f
`
`,
`
`ASTIGMATISM
`
`

`

`US. Patent May 29, 1990
`
`Sheet 30f15
`
`4,929,066
`
`Fig. 5
`
` -0.08
`
`SPHERICAL ABERRATION
`
`ASTIGMATISM
`
`0.08
`
`

`

`Sheet 40f15
`
` .
`
`US. Patent May 29, 1990
`
`SPHERICAL ABERRATION
`
`4,929,066
`
`.08
`
`ASTIGMATISM
`
`

`

`US. Patent May 29, 1990
`
`Sheet 50f15
`
`4,929,066
`
`Fig. 9
`
` —— d-line
`
`------ C-line
`—-—— F-line
`
`SPHERICAL ABERRATION
`
`0.
`
`.
`
`ASTIGMATISM
`
`

`

`US. Patent May 29, 1990
`
`‘Sheet 6 of 15
`
`4,929,066
`
`Fig. 11
`
`rs mo 1
`
`
`
`_i
`
`an
`
`ee
`
`
`
`d-line
`== C-line
`—~""—~ F~line
`
`
`-0. 06
`
`~
`SPHERICAL ABERRATION
`
`
`0.06
`
`-0.02
`
`ASTIGMATISM
`
`0.02
`
`

`

`
`
`US. Patent—May29, 1990 Sheet 70f15 4,929,066
`
`
`
`Fig. 13
`
` ASTIGMATISM
`
`

`

`US. Patent May 29, 1990
`
`Sheet 80f15
`
`4,929,066
`
`Fig. 15
`rs
`
`7 fe
`
`rs
`
`Ko
`
`
`0.1
`
`
`
`ASTIGMATISM
`
`

`

`US. Patent May 29, 1990
`
`Sheet 90f15
`
`4,929,066
`
`Fig. 17
`
`re 7 re
`
`fs
`
`Nn
`
`me
`
`ha
`
`hs he 7 he
`
`rf & Fs
`
`Fig. 18
`
`
`
`———— d-line
`---—--- C-line
`
`——-—— F-line
`
`-0.20
`
`0.20
`
`
`
`0.30
`
`SPHERICAL ABERRATION
`
`ASTIGMATISM
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet 10 0f15
`
`4,929,066
`
`h Rw tw Ps
`
`ha ns he f7 ha
`
`0.15
`
`SPHERICAL ABERRATION
`
`0.15
`
`0.25
`
`ASTIGMATISM
`
`0.25
`
`

`

`US. Patent May 29, 1990
`
`Sheet 11 0f15
`
`4,929,066
`
`Fig. 21
`
`nm @ Bf & Fs
`
`rg
`
`rio
`
`ha
`
`fis
`
`he fs
`
`fe 7 ha Mm
`
`
`
`
`
`-0.12
`
`SPHERICAL ABERRATION
`
`‘
`
`ASTIGMATISM
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet 120f15
`
`4,929,066
`
`Fig. 23
`
`:
`
`ho sn ha hs
`
`nN ff - Is
`
`ra hs he nv hg rs
`
`0.12
`
`,
`SPHERICAL ABERRATION
`
`0.12
`
`~0.25
`
`ASTIGMATISM
`
`0.25
`
`

`

`US. Patent May 29, 1990
`
`Sheet 13 0f 15
`
`4,929,066
`
`PRIOR ART
`
`Fic: 25
`
`|
`
`re.
`
`rr SYMMETRICAL
`
`CENTER
`
`Fig. 26
`PRIOR ART
`
`Ss
`
`os
`
`4.0°
`
` 0.06
`
`SPHERICAL ABERRATION
`
`ASTIGMATISM
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet 140f15
`
`4,929,066
`
`

`

`US. Patent
`
`May29, 1990
`
`Sheet 15 of 15
`
`4,929,066
`
`Fig. 29
`
`13
`
`

`

`TELECENTRIC IMAGE-FORMING OPTICAL
`SYSTEM FOR LARGE IMAGESIZE
`
`BACKGROUND OF THE INVENTION
`
`5
`
`15
`
`25
`
`30
`
`35
`
`1. Field of the Invention
`Thepresent invention relates to a telecentric image-
`forming optical system through which a principal ray
`passes in a direction parallel to the optical axis of the
`system, and more particularly, to a telecentric image-
`forming optical system in which an imagesize is large
`compared to the distance between the object and the
`image, and the magnification of the system is one or
`approximately one.
`2. Description of the Prior Art
`In knowntelecentric image-forming optical systems,
`the secondary focal pointof a first lens group having a
`positive focal length and disposed in front of a lens
`disposed at the center of the optical system coincides .
`with the principal focal point of a second lens group
`which also has a positive focal length and which is
`disposed behind the center lens. In this arrangement,
`when an object (or a real image formed by an optical
`system disposed in front of the first lens group) is placed
`in the vicinity of the principal focal point of the first lens
`group, a real image is formed in the vicinity of the sec-
`ondary focal point of the second lens group. The magni-
`fication of the real image corresponds to the ratio of the
`focal lengths of the lens groups.
`If the intervals between the principal points of the
`lenses are ignored, the distance between the object and
`the image is approximately twice as great as the sum of
`the focal lengths of the lens groups.
`;
`In such a system, it is difficult to create a wide angle
`view. Therefore, if a large image size is required, the
`optical system itself must be large, which causes an
`apparatus which incorporates the optical system to be
`undesirably large.
`Apparatuses in which the optical system is incorpo-
`rated include an image reader for reading an original
`documentby a solid image sensor (for example, CCD),
`and exposing apparatus for printing mask patterns of an
`IC and an LSI on a semiconductor wafer, a scanning
`recording apparatus such as a laser plotter, a laser
`printer and thelike. A telecentric image-forming optical
`system is useful in these apparatuses because the magni-
`fication of such a system does not vary if the object
`distance is changed. Further, using a telecentric image-
`forming optical system prevents degradation of resolu-
`tion and reduction ofthe intensity of marginal rays.
`SUMMARY OF THE INVENTION
`
`45
`
`50
`
`invention solves the above-described
`The present
`problems and has as its object to provide a telecentric
`image-forming optical system having the following
`construction.
`Thetelecentric image-forming optical system in ac-
`cordance with the present invention comprises a first
`lens group and a second lens group. Thefirst group
`includes a double-convex lens, a meniscus lens whose
`convexside faces the object or a plano-convex lens, and
`a double-concavelens arranged in this order as viewed
`from the object. The second lens group includes a dou-
`ble-convex lens, a meniscus lens whose convex side
`faces the image or a plano-convex lens, and a double-
`concave lens arranged in this order as viewed from the
`image. The secondary focal point ofthe first lens group
`and the principal focal point of the second lens group
`
`55
`
`60
`
`65
`
`1
`
`4,929,066
`
`2
`substantially coincide with each other at a first point. A
`third double-convex lens having a positive focal length
`is disposed in the center between thefirst lens group and
`the secondlens group. Thethird lens is disposed in the
`vicinity of the first point.
`Since the double-convex lens is interposed between
`the first and second lens groups, the telecentric charac-
`teristic is maintained, and the object distance and the
`image distance are short. Accordingly,
`the total dis-
`tance between the object and the imageis short.
`The refracting power ofthe third convex lens can
`create a large curvature of field. In order to prevent
`such an occurrence, a concave lens having a negative
`focal length is disposed within each of the first and
`second lens groups. The concave lenses correct the
`curvature of field, whereby the image surface can be
`flattened and the image size can be enlarged.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The objects and the features of the present invention
`will become apparent from the following description
`whentaken in conjunction with preferred embodiments
`thereof with reference to the accompanying drawings
`in which:
`FIG.1 is a lens arrangement view showing the essen- _
`tial construction and arrangement of a telecentric im-
`age-forming optical system in accordance with the pres-
`ent invention;
`FIG, 2 shows aberration curves showing the spheri-
`cal aberration and the astigmatism of the first embodi-
`ment shown in FIG.1;
`FIG.3 is a lens arrangement and construction view
`showing a second embodiment;
`FIG. 4 showsaberration curves of the second em-
`bodiment;
`FIG.5 is a lens construction and arrangement view
`showing a third embodiment;
`FIG. 6 shows aberration curves of the third embodi-
`ment;
`FIG. 7 is a lens construction and arrangement view
`showing a fourth embodiment;
`FIG.8 showsaberration curves of the fourth embodi-
`mient;
`FIG,9 is a lens construction and arrangement view
`showing a fifth embodiment;
`FIG. 10 shows aberration curvesofthe fifth embodi-
`ment;
`FIG.11 is a lens construction and arrangement view
`showing a sixth embodiment;
`FIG.12 showsaberration curves of the sixth embodi-
`ment;
`FIG.13 is a lens construction and arrangement view
`showing a seventh embodiment;
`FIG. 14 showsaberration curves of the seventh em-
`bodiment;
`FIG.15 is a lens construction and arrangement view
`showing an eighth embodiment;
`FIG. 16 shows aberration curves of the eigth embodi-
`ment;
`FIG.17 is a lens construction and arrangement view
`showing a ninth embodiment;
`FIG. 18 showsaberration curves of the ninth embodi-
`ment;
`FIG.19 is a lens construction and arrangement view
`showing the entire arrangementofthe fifth embodiment
`for comparison with the lens system shown in FIG.21;
`
`

`

`4,929,066
`
`4
`FIG. 2 shows aberration curves showing the spheri-
`cal aberration and the astigmatism of the first embodi-
`ment.
`In the first embodiment, the lens system is composed
`of all single lenses, but preferably some lenses are ce-
`mented to each other with a glass material having a
`different refractive index and dispersion so as to correct
`chromatic aberrations. The glass material herein in-
`cludes a plastic material.
`In each of the second through eighth embodiments
`(described hereinafter),
`lenses are cemented to each
`other to correct chromatic aberrations and flatten image
`surfaces. In order to simplify the drawings, a plane face
`at a right angle to the optical axis is shownat the left of
`each drawing. This plane face represents a vertical cut
`throughthe center lens. Only lenses disposed behind the
`plane face are shown.
`Accordingly, in the second through eighth embodi-
`ments,
`rj=co, which corresponds
`to the above-
`described plane face.
`Each of the drawings (FIG. 3 through 16) of spheri-
`cal aberrations and astigmatisms in the second through
`eighth embodiment showsonly the portion behind the
`plane face. Therefore, when the lens groups are ar-
`ranged symmetrically with respect to the plane face in
`each of the second through eighth embodiments,
`the
`spherical aberration and the astigmatism are more than
`twice as large as those shown in the drawings.
`Second Embodiment
`
`25
`
`3
`FIG. 20 showsaberration curves of the lens system
`shown in FIG. 19;
`FIG.21is a lens construction and arrangement view
`showing a tenth embodiment;
`.
`FIG.22 shows aberration curves of the tenth embodi-
`ment;
`:
`FIG.23 is a lens construction and arrangement view
`showing an eleventh embodiment;
`FIG. 24 shows aberration curves of the eleventh
`embodiment;
`FIG. 25 shows a knowntelecentric image-forming
`optical system. The figure only shows the portion
`which is behind the point at which the focal points of
`two lens groups of the system coincide with each other;
`FIG.26 is a view showing an aberration curve of the
`prior art system shown in FIG.25;
`FIG.27 is a schematic perspective view of an appara-
`tus to which an optical system in accordance with the
`present invention may be applied;
`FIG. 28 is an explanatory view showing the move-
`ment of a scanning head of the apparatus; and
`FIG.29 is an explanatory view showing the scanning
`head portion.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`First Embodiment
`
`A first embodiment shown in FIG. 1 showsthe fun-
`damental construction and arrangementofa telecentric
`image-forming optical system, in accordance with the
`present invention, in which two lens groups are sym-
`metrical about the central plane of a double-convex lens
`(hereinafter referred to as the “center lens”). As shown,
`the center lens is disposed in the center of the optical
`system. Lens data for the lens groups shown in FIG. 1
`are listed in TABLE1.
`
`TABLE1
`
`r
`d
`1
`v
`
`1
`352.25
`6,3
`1.603
`65.4
`2
`—116,50
`0.6
`3
`45.87
`14.7
`4
`545.00
`21.1
`5
`—68.90
`63
`6
`33.95
`29.3
`7
`72.00
`8.0
`8
`—72.00
`29.3
`9
`—33.95
`6.3
`10
`68.90
`21.1
`11
`—545.00
`14.7
`12
`—45.87
`0.6
`13
`116,50
`6.3
`14
`—352.25
`do: 127.39;
`Distance between object and image: 419.38;
`Image-forming magnification: 1.0;
`Dimension of image plane: 40 ;
`F-number: 9.1 (NA-:0.055)
`
`1.620
`
`1.616
`
`1.486
`
`1.616
`
`1.620
`
`1.603
`
`63.5
`
`31.0
`
`81.8
`
`31.0
`
`63.5
`
`65.4
`
`where
`(r) represents the radius of curvature of the faces of
`the respective lenses;
`(do) shows the distance between the object and the
`face of curvature rj);
`d, through d)3 denote the center thickness of the
`respective lenses or the interval between the lenses
`along the optical axis;
`(n) represents the refractive indexes of the respective
`lenses relative to a wavelength of 587.6 nm;
`(3) shows the Abbe numberofthe respective lenses.
`
`FIG. 3 is a lens construction and arrangement view
`showing a second embodiment in which one lens group
`shows cemented together to correct the chromatic ab-
`erration and flatten the image surface. Lens data for the
`respective lens groups shown in FIG. 3 arelisted in
`TABLE3.
`
`35
`
`
` TABLE2
`r
`d
`n
`v
`
`1
`co
`44
`1.593
`67.9
`2
`—95.83
`30.0
`3
`—40.70
`6.9
`4
`75,16
`22.8
`5
`—2380.00
`12.5
`6
`—33.57
`3.9
`7
`— 60.76
`0.6
`8
`146.55
`69
`9
`—463.87
`Focal length: 100;
`
`
`1,595
`
`1.697
`1.648
`
`1.697
`
`35.5
`
`55.6
`33.8
`
`55.6
`
`where
`(r) represents the radius of curvature of the faces of
`the respective lenses;
`d, through dg denote the thickness of the respective
`lenses or the distance between the adjacent faces of
`the lenses;
`(n) represents the refractive index of the respective
`lenses relative to a wavelength of 587.6 nm;
`(3) shows the Abbe numberofthe respective lenses.
`FIG.4 are aberration curves showing the spherical
`aberration and the astigmatism of the second embodi-
`ment.
`
`Third Embodiment
`
`FIG. 5 showsa lens construction and arrangement
`view showing a third embodiment in which twolens
`groups are cemented to each other to correct the chro-
`matic aberration and flatten the image surface. Lens
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`

`4,929,066
`
`6
`TABLE5-continued
`r
`d
`
`n
`
`5
`data of the respective lens groups shown in FIG.5 are
`listed in TABLE3.
`
`TABLE3
`r
`d
`n
`v
`
`l
`oo
`43
`1.620
`60.3
`2
`—99,00
`30.3
`3
`—39.60
`5.0
`4
`— 18.80
`18
`5
`78.35
`22.55
`6
`—2400.00
`12.4
`7
`=—37.10
`3.8
`8
`—58.80
`0.6
`9
`144.80
`6.8
`10
`—457.35
`Focal length: 100;
`F-number: 8.3;
`Back focus: 120.74;
`Image size: 40 & (angle of view: 23°)
`
`1.623
`1.613
`
`1.694
`1.651
`
`1.694
`
`58.2
`37.0
`
`53.8
`38.2
`
`53.8
`
`v I
`
`magesize: 40 & (angle of view: 23°)
`
`FIG. 10 are aberration curves showing the spherical
`aberration and the astigmatism of the fifth embodiment.
`Sixth Embodiment
`
`FIG. 11 shows a lens construction and arrangement
`view showing a sixth embodiment in which three lens
`groups are cemented to each other to correct the chro-
`matic aberration and flatten the image surface. Lens
`data for the respective lens groups shown in FIG.11 are
`listed in TABLE6.
`
`10
`
`i5
`
`FIG. 6 are aberration curves showing the spherical
`aberration and the astigmatism of the third embodiment.
`Fourth Embodiment
`
`20
`
`FIG.7 is a lens construction and arrangement view
`showing a fourth embodiment in which,similarly to the
`third embodiment, two lens groups are cemented to
`each other. Lens data for the respective lens groups
`shownin FIG.7 are listed in TABLE 4.
`
`TABLE4
`d
`44
`28.8
`7.0
`23.4
`13.0
`3.7
`0.6
`13.0
`3.7
`
`T
`0
`1
`— 102.60
`2
`—42.70
`3
`80.90
`4
`— 1930.00
`a
`—37.20
`6
`—60,90
`7
`151.20
`8
`— 132,00
`9
`—404.00
`10
`Focal length: 100;
`F-number: 8.3;
`Back focus: 118.82;
`Image size: 40 o (angle of view: 23°)
`
`n
`1.620
`
`1.620
`
`1.694
`1.648
`
`1.694
`1.689
`
`v
`60.3
`
`36.3
`
`53.8
`33.8
`
`53.8
`31.1
`
`25
`
`30
`
`35
`
`FIG. 8 are aberration curves showing the spherical
`aberration and the astigmatism of the fourth embodi-
`ment.
`
`45
`
`Fifth Embodiment
`
`FIG. 9 shows a lens construction and arrangement
`view showing a fifth embodiment in which, similarly to
`the third and fourth embodiments, two lens groups are
`cemented to correct the chromatic aberration andflat-
`ten the image surface. Lens data for the respective lens
`groups shownin FIG.9 are listed in TABLE5.
`TABLE 5
`
`r
`d
`n
`v
`
`l
`oo
`43
`1.620
`60.3
`2
`—98.45
`30.8
`3
`—41.00
`5.0
`4
`—18.45
`1.8
`5
`77.75
`22.4
`6
`—2100.00
`3.8
`7
`144.00
`12.3
`8
`—58.45
`0.6
`9
`144.00
`6.8
`10
`455.30
`Focal length: 100;
`F-number: §.3;
`Back focus: 118.38;
`
`1.620
`1.613
`
`1.651
`1.694
`
`1.694
`
`60.3
`37.0
`
`38.2
`53.8
`
`53.8
`
`35
`
`65
`
`TABLE6
`r
`d
`n
`v
`
`1
`oo
`1.0
`1.613
`444
`2
`25.00
`3.6
`1.613
`58.5
`3
`—95.50
`31.0
`:
`4
`—39.40
`4.8
`1.620
`5
`15.50
`1.8
`1.613
`6
`75.80
`21.7
`if.
`—770.00
`3.6
`8
`141.00
`12.0
`9
`—57.30
`0.3
`10
`143.20
`6.5
`ll
`— 394.00
`Focal length: 100;
`F-number:8.3;
`Back focus: 118.49;
`Imagesize: 40 @ (angle of view: 23°)
`
`1.613
`1.694
`
`1.694
`
`60.3
`44.4
`
`44.4
`53.8
`
`53.8
`
`FIG.12 are aberration curves showing the spherical
`aberration and the astigmatism of the sixth embodiment.
`Whenthe lenses shown in FIG. 11 are symmetrical
`with respect to the above-described plane surface, two
`lenses are cemented to the double-convex centerlens.
`Thus, the center lens is disposed at the center of three
`lenses. In this lens system, five convex lenses are made
`of Kruz-Flint glass. The use of Kruz-Flint glass reduces
`the chromatic aberration by } to 4 times.
`Seventh Embodiment
`
`FIG. 13 shows a lens construction and arrangement
`view showing a seventh embodimentin which the com-
`bination of lenses is different from those of the third
`through fifth embodiments, but similarly to these three
`embodiments, two lens groups are cemented to each
`other, Lens data for the respective lens groups shown in
`FIG.13 are listed in TABLE 7.
`
`TABLE 7
`
`Tr
`d
`n
`v
`co
`4.3
`1.620
`60.3
`1
`—98.9
`30.8
`2
`—41.15
`Lg
`3
`30,2
`5.0
`4
`78.75
`22.65
`5
`— 1850.00
`16,00
`6
`— 59.35
`0.5
`7
`144.70
`12.5
`8
`— 120.00
`3.5
`9
`—457.40
`10
`Focal length: 100;
`F-number: 8.3;
`Back focus: 111.37;
`Imagesize: 40 @ (angle of view: 23°)
`
`1595
`1.620
`
`1.694
`
`1.694
`1.648
`
`a549
`60.3
`
`53.8
`
`53.8
`33.8
`
`

`

`7
`FIG. 14 shows aberration curves showing the spheri-
`cal aberration and the astigmatism of the seventh em-
`bodiment. .
`
`4,929,066
`
`Eighth Embodiment
`FIG. 15 shows a lens construction and arrangement
`view showing an eighth embodimentin which,similarly
`to the seventh embodiment, two lens groups are ce-
`mented to each other. Lens data for the respective lens
`groups shownin FIG. 15 are listed in TABLE8.
`TABLE 8
`i.
`d
`n
`v
`
`1
`oo
`43
`1,620
`60.3
`2
`—98.90
`30.7
`3
`—42.10
`5.0
`4
`—19.00
`1.8
`5
`82.60
`22.65
`6
`es)
`16.00
`7
`—60.55
`0.5
`8
`144.70
`12.5
`9
`— 120.00
`3.5
`10
`—457.40
`Focal length: 100;
`F-number: 8.3;
`Back focus: 112.07;
`Image size: 40 @ (angle of view: 23°)
`
`1.620
`1.613
`
`1.694
`
`1.694
`1.651
`
`60.3
`37.0
`
`53.8
`
`53.8
`38.2
`
`FIG. 16 illustrates aberration curves showing the
`spherical aberration and the astigmatism of the eighth
`embodiment.
`The second through eighth embodiments are modifi-
`cations of the first embodiment in which one lens group
`consists of lenses cemented to each other with a glass
`material having a refractive index and a dispersive
`power different from those of the lenses so as to correct
`chromatic aberration and flatten the image surface. In
`each of these embodiments, a double-convex lens is
`disposed in the center of the lens system.
`FIG. 25 shows an example of knowntelecentric im-
`age-forming optical systems in which a double-convex
`lens is not disposed at the center of the lens system. Lens
`data for the respective lenses are listed in TABLE 9.
`TABLE9
`d
`10.0
`3.0
`
`n
`1.618
`1.689
`
`v
`52.7
`31.2
`
`Tr
`85.5
`-343
`— 136.85
`
`1
`2
`3
`do: 96.0;
`Focal length: 100;
`F-number: 8.3;
`Back focus: 94.60;
`Image size: 14
`(angle of view: 8°)
`
`where
`(r) showsthe radii of curvature of the lenses;
`(d) represents the thickness of the lenses;
`(n) denotes the refractive index of the lenses relative
`to the wavelength of 587.6 nm;
`(v) indicates Abbe number;
`(do) denotes the distance between an object and the
`face of curvature r3 (+136.85) when lenses are
`arranged symmetrically with respect to the center
`of the lens system shown in FIG,25.
`FIG. 26 showsthe spherical aberration and the astig-
`matism of the telecentric image-forming optical system
`shown in FIG. 25.
`Comparing the above-described embodiments with
`the knowntelecentric image-forming optical system,it
`is apparent that the telecentric image-forming optical
`‘system in accordance with the present invention has a
`
`15
`
`25
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`wider angle of view. Thatis, the total lengths of the
`telecentric image-forming optical system of the above-
`described embodiments are almost equal to the known
`telecentric image-forming optical system shown in FIG.
`25, but the dimension of the image plane which can be
`formedis substantially three times as great as that of the
`knowntelecentric image-forming optical system.
`In each of the second through eighth embodiments,
`the principal focal point of the lens system does not
`coincide with the center of the lens system, butis dis-
`posed in the vicinity thereof. This is because the charac-
`teristics of the telecentric optical system is not degraded
`by the spherical aberration of the lens system. Actually,
`the position of a minimum circle of confusion formed by
`a parallel light flux from an image incident on the lens
`system coincides with the above-described center.
`Accordingly,
`the symmetrical arrangement of the
`lens groups about the above-described planeface in the
`second through eighth embodiments allows formation
`of a telecentric image-forming optical system in which
`the object size is magnified by one, i.e., a large angle of
`view is wide, that is, the object size is large.
`The same effect can be also obtained by making a
`position a little in front of the above-described plane
`face the reference face about which the lens system is
`arranged symmetrically. In this case, an air space is
`provided in the center face of the double-convex lens.
`It is possible to obtain the same effect by combining
`the lens systems of the second through eighth embodi-
`ments. A ninth embodiment (described below)is a com-
`bination of the seventh and eighth embodiments.
`Ninth Embodiment
`
`FIG. 17 shows a lens construction and arrangement
`view of a ninth embodiment in which the lens systems
`of the seventh and eighth embodiments are combined
`with each other.
`In this embodiment, astigmatism is corrected by lens
`groups disposed forwards and backwards from the
`plane face. Astigmatism in this embodimentis smaller
`than that of a lens system perfectly symmetrical with
`respect to the center-positioned plane face. Lens data
`for the respective lens groups shown in FIG. 17 are
`listed in TABLE 10.
`
`TABLE 10
`r
`d
`n
`v
`
`I
`457.40
`3.5
`1.648
`33.8
`2
`120.00
`12.5
`1.694
`53.8
`3
`— 144,70
`0.5
`4
`59.35
`16,0
`5
`1850.00
`22.65
`6
`—78.75
`5.0
`7
`— 30.20
`1.8
`8
`41.15
`30.8
`9
`98.90
`8.6
`10
`—98,90
`30.7
`1
`—42.10
`5.0
`12
`—19.00
`1.8
`13
`82.60
`22,65
`14
`oo
`16.00
`15
`—60.55
`0.5
`16
`144.70
`12.50
`17
`— 120.00
`3.5
`18
`—457.40
`dg (distance between object and face of curvature r1):
`111.37;
`Distance between object and image: 417.44;
`Image-forming magnification: 1;
`
`1.694
`
`1.620
`1.595
`
`1.620
`
`1.620
`1.613
`
`1.694
`
`1.694
`1.651
`
`53.8
`
`60.3
`35.5
`
`60.3
`
`60.3
`37.0
`
`53.8
`
`53.8
`38.2
`
`

`

`9
`FIG. 18 illustrates aberration curves showing the
`spherical aberration and the astigmatism of the ninth
`embodiment.
`FIG. 19 shows the lens system in which the lens
`system ofthe fifth embodiment shown in FIG.9 is ar-
`ranged symmetrically about
`the plane face rj (also
`shown in FIG. 9). This lens system constitutes an im-
`age-forming optical system in which the image of an
`object is magnified by one. This lens system is shown
`for comparison with the lens system shown in FIG.21.
`The lens data for the lenses shown in FIG. 19 are
`listed in the following TABLE 11.
`TABLE 11
`d
`6.8
`0.6
`12.3
`3.8
`22.4
`1.8
`5.0
`30.8
`8.6
`30.8
`5.0
`L8
`22.4
`3.8
`12.3
`0.6
`6.8
`
`4,929,066
`
`10
`TABLE12
`c
`d
`n
`v
`
`1
`455.30
`6.8
`1.694
`53.8
`2
`— 144.00
`0.6
`3
`58.45
`12.3
`4
`— 144.00
`3.8
`5
`2,100.00
`22.4
`6
`—77.75
`L8
`7
`18.45
`5.0
`8
`41,00
`30.8
`9
`98.45
`7.74
`10
`—78.76
`24,64
`1
`—32.80
`4.0
`12
`— 14.76
`1.44
`13
`62.20
`17.92
`14
`— 1680.00
`3.04
`15
`115,20
`9.84
`16
`—46.76
`0.48
`17
`115.20
`5.44
`18
`— 364.24
`dp (distance between object and face of curvature rj):
`118.38;
`Distance between object and image: 371.12;
`Image-forming magnification: 0.8;
`Imagesize: 32 ;
`F-number: 8.3 (NA: 0.06)
`
`1.694
`1.651
`
`1.613
`1.620
`
`1.620
`
`1.620
`1.613
`
`1.651
`1.694
`
`1.694
`
`53.8
`38.2
`
`37.0
`60.3
`
`60.3
`
`60.3
`37.0
`
`38.2
`53.8
`
`53.8
`
`FIG. 22 illustrates aberration curves showing the
`spherical aberration and the astigmatism of the tenth
`embodiment.
`When a telecentric image-forming optical system
`which has an image-forming magnification (other than
`one) and forms a large image size is constituted, the
`following method may be adopted: One need notpro-
`portionally magnify or reduce the radii of curvature and
`the distances between adjacent faces of the lenses of the
`lens group as is done in the tenth embodiment. Instead,
`for example, a desired image-forming magnification can
`be obtained by shifting the double-convex lens from the
`center of the lens system.
`Eleventh Embodiment
`
`The lens groups of an eleventh embodiment are ar-
`ranged by shifting a double-convex lens from the center
`ofthe lens system. FIG. 23 showsthe lens arrangement
`of the lens system. Lens data for the respective lens
`groups shown in FIG.23 are listed in TABLE 13.
`TABLE13
`d
`6.8
`0.6
`12.3
`3.8
`22.4
`1.8
`5.0
`40.0
`8.6
`17.85
`5.0
`Lg
`22.4
`3.8
`12.3
`0.6
`6.8
`
`n
`1.694
`
`1.694
`1.651
`1.613
`1.623
`
`vr
`418.45
`1
`— 144.00
`2
`58.45
`3
`— 144.00
`4
`2460.00
`5
`— 76.43
`6
`17.48
`7
`40.49
`8
`114.46
`9
`86.15
`10
`—40.49
`ll
`— 17.48
`12
`76.43
`13
`—2460.00
`14
`144.00
`15
`—58.45
`16
`144.00
`17
`—418.45
`18
`do (distance between object and face of curvature r):
`125.5:
`Distance between object and image: 410.24.
`Image-forming magnification: 0.865;
`Image size: 34.64 d;
`F-number: 8.9 (NA:0.056)
`
`1.620
`
`1.623
`1.613
`
`1.651
`1,694
`
`1.694
`
`v
`53.8
`
`53.8
`38.2
`37.0
`58.2
`
`60.3
`
`58.2
`37.0
`
`38.2
`53.8
`
`53.8
`
`10
`
`15
`
`25
`
`30
`
`35
`
`45
`
`55
`
`65
`
`v
`53.8
`
`53.8
`38.2
`
`37.0
`60.3
`
`60.3
`
`60.3
`37.0
`
`38.2
`53.8
`
`53.8
`
`n
`1.694
`
`1.694
`1.651
`
`1,613
`1.620
`
`1.620
`
`1.620
`1.613
`
`1.651
`1.694
`
`1.694
`
`r
`455.30
`1
`— 144.00
`2
`58.45
`3
`— 144.00
`4
`2100.00
`5
`77.75
`6
`“18.45
`-
`41.00
`8
`98.45
`9
`—98.45
`10
`—41.00
`11
`— 18.45
`12
`77.75
`13
`—2100.00
`14
`144.00
`15
`—58.40
`16
`144.00
`I?
`—455.30
`18
`do (distance between object and face of curvature ry):
`118.38;
`Distance between object and image: 412.35;
`Image-forming magnification: 1;
`Image size: 40 ¢;
`F-number: 8.3 (NA: 0.06)
`
`FIG. 20 illustrates aberration curves showing the
`spherical aberration and the astigmatism of the lens
`system shown in FIG. 19.
`Thefocal length of the lens group disposed in front of
`the center of the lens system need not be the same as the
`focal length of the lens group disposed behind the cen-
`ter of the lens system. For example, a telecentric image-
`forming optical system whose image-forming magnifi-
`cation is M times an object size can be constituted as
`follows: The radius of curvature and the distance be-
`tween adjacent faces of the lenses of a lens group dis-
`posed behind the center of the lens system are propor-
`tionally magnified or reduced by M times those of the
`lens group disposed in front of the center of the lens
`system.
`
`Tenth Embodiment
`
`FIG.21 illustrates a lens construction and arrange-
`ment view showing a tenth embodiment in which the
`construction of the lenses disposed in front of the center
`of the lens system are the same as those ofthe fifth
`embodiment and the lenses disposed behind the center
`of the lens system are constructed by proportionally
`reducing the image-forming magnification of the lens
`system of the fifth embodiment by 0.8 times. Thus, a
`telecentric image-forming optical system whose image-
`forming magnification is 0.8 times is constituted. Lens
`data for the respective lens groups shownin FIG.21 are
`listed in TABLE 12.
`
`

`

`4,929,066
`
`— 5
`
`25
`
`30
`
`35
`
`11
`FIG. 24 illustrates aberration curves showing the
`spherical aberration and the astigmatism of the eleventh
`embodiment.
`;
`In the eleventh embodiment, the double-convex lens
`is not cemented, and therefore the lens is not achro-
`matic. Therefore, if the double-convex lens is shifted
`such that the lens groups are unsymmetrical, a lateral
`chromatic aberration occurs. However, the magnifica-
`tion of a telecentric image-forming optical system is not
`varied even if the object distance is varied. Thus, an
`appropriate selection of the object distance (125.5 in this
`embodiment) corrects the lateral chromatic aberration
`without varying the image-forming magnification.
`As apparent from the foregoing description, the pres-
`ent invention, has a relatively simple lens construction.
`The arrangement provides a telecentric image-forming
`optical system in which the dimensions of an image
`plane may be large compared with the distance between
`the object and the image surface. Further, an object
`may be magnified or reduced.
`Furthermore, when the telecentric image-forming
`optical system in accordance with the present invention
`is used within an apparatus, the apparatus can be com-
`pactly manufactured because the length of the optical
`system is compact.
`
`12
`great as, for example, 655 X 869mm. The seconddiffer-
`ence is that it has a resolution as high as 1000~2000
`lines/inch. Thatis, the apparatus 100 reads data from a
`great area and at a high resolution. The apparatus 100 is
`required to read out the data as fast as possible. But the
`following problem arises.
`It is difficult to place a block copy layout sheet 13 on
`the glass 12 with no spaceleft therebetween. Evenif the
`block copy layout sheet is secured to the frame of the
`glass 12, the sheet flexes on the glass. In this case, a
`small mechanical error can greatly affect the optical
`system of the apparatus 100. In order to maintain a high
`resolution irrespective of the position of the layout
`sheet, magnification of an image on an image surface
`should not be varied even if there is a small change in
`the block copy layout sheet’s position. It is for this
`reason that a telecentric image-forming optical system is
`used within the scanning head. Sheet are frequently
`pasted on some regions of the block copy layout sheet
`13, so that the surface of the block copy layout sheet 13
`becomes irregular or stepshaped. The problems caused
`by such irregularity can also be solved by the telecen-
`tric image-forming optical system.
`In order to shorten the period of time required to read
`data, the scanning head 16 must scan the sheet 13 at a
`high speed. However, the scanning speed of the scan-
`Application Example
`ning head 16 is restricted to maintain a predetermined
`high resolution. To this end, the scanning width of a
`An application example using an optical system in
`raster should be great. This is possible with an optical
`accordance with the present
`invention is described
`hereinbelow. The application example relates to a read
`system which has a wide angle of view. However,in the
`apparatus for reading a block copy layout sheet to cre-
`Prior Art, it has been difficult to make a telecentric
`ate a prepress in a printing process.
`image-forming optical system with a wide angle of
`A block copy is formed at the initial stage of the
`view. If the angle of view is made wide without making
`prepress. The prepress specifies the arrangements of
`any countermeasures, the optical system itself becomes
`large. Thatis, the length of the optical system becomes
`letters, line drawings, photographs and the like in a
`sheet to be printed. The specification accurately per-
`long. It is difficult to use such a long optical system
`formed onalayout sheet is called a layout block copy or
`within the scanning head 16. In order to obtain a read
`a block copy layoutsheet.
`range for the scanning head 16 to travel, the scanning
`The block copy layout sheet is formed byadigitizer
`head 16 must be compact. Thus, to shorten the length of
`40
`or an automatic drafting machine. An original docu-
`the optical system a wide angle of view is necessary. In
`mentto be laid out in a specified position is processed by
`this sense, the telecentric image-forming optical system
`a scanner and stored in a storing medium in the form of
`of the present invention in which the angle of view is
`digital data. Data for laying out an image is necessary to
`wide compared wit