US008233224B2
`
`(12) United States Patent
`Chen
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,233,224 B2
`Jul. 31, 2012
`
`(54) IMAGING LENS SYSTEM
`
`(56)
`
`References Cited
`
`(*) Notice:
`
`U.S. PATENT DOCUMENTS
`2001/0015856 A1* 8/2001 Yoneyama .................... 359/687
`2009.0122423 A1* 5, 2009 Park et al. ..
`... 359,764
`2010/0220229 A1* 9, 2010 Sano ............................. 348/340
`k .
`cited by examiner
`
`Primary Examiner — Jordan Schwartz
`(74) Attorney, Agent, or Firm — Bacon & Thomas, PLLC
`
`(75) Inventor: Chun-Shan Chen, Taichung (TW)
`rsr rr
`(73) Assignee: Largan Precision Co., Ltd., Taichung
`(TW)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 288 days.
`(21) Appl. No.: 12/6S4,912
`ppl. No.:
`9
`(22) Filed:
`Jan. 8, 2010
`(65)
`Prior Publication Data
`US 2011/0013069 A1
`Jan. 20, 2011
`O
`O
`Foreign Application Priority Data
`
`(30)
`
`ABSTRACT
`(57)
`This invention provides al imaging lens system including, in
`order from an object side to an image side: a first lens with
`positive refractive power having a convex object-side Surface;
`a second lens with negative refractive power; a third lens
`having a concave image-side Surface; a fourth lens with posi
`tive refractive power; a fifth lens with negative refractive
`Jul. 14, 2009 (TW) ............................... 98.123694. A power having a concave image-side Surface, at least one Sur
`(51) Int. Cl
`face thereofhaving at least one inflection point; and an aper
`(2006.01)
`Goi o/60
`ture stop disposed between an imaged object and the third
`(2006.015
`GO2B 13/18
`lens. The on-axis spacing between the first lens and second
`(52) U.S. Cl. ......................... 359/764; 35.9/763; 359/714
`e R T12, t
`st SEE, system is f.
`(58) Field of Classification Search .......... songs 76,
`and they satisfy the relation: 0.5-(T12/Dx
`359/754 757, 771 773,776 778, 713 714
`See application file for complete search history.
`27 Claims, 13 Drawing Sheets
`
`
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 1 of 13
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`US 8,233,224 B2
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`111-122-1 / 132
`112-131-1 141
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`Fig. 1
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 3 of 13
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`US 8,233,224 B2
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`301
`
`y \ 7
`a
`302\321 ?
`311-322-1 1332
`312-1331-1 341
`
`342
`
`Fig. 3
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 5 of 13
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`US 8,233,224 B2
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`\ 7
`Y1
`501-1 502\521 ?
`511-522- 532
`512-531-1 541
`
`Fig. 5
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`APPL-1008 / Page 7 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 7 of 13
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`US 8,233,224 B2
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`TABLE 1
`(Embodiment 1)
`f = 5.44 mm, Fno - 2.9, HFOV = 33.0 deg.
`Curvature Radius Thickness Material
`Index
`
`Abbe it
`
`h
`
`Surface #
`
`O
`1
`2
`3
`4.
`5
`6
`7
`8
`9
`10
`11
`12
`13
`14
`
`Object
`Ape. Stop
`Lens 1
`
`Lens 2
`
`Lens 3
`
`Lens4
`
`LenSS
`
`IR-filter
`
`Image
`
`Plano
`Plano
`1.54469 (ASP)
`5.13230 (ASP)
`285.35120 (ASP)
`5.07630 (ASP)
`2.37564 (ASP)
`2.18085 (ASP)
`-1.60878 (ASP)
`-1.26807 (ASP)
`3.00470 (ASP)
`1.73617 (ASP)
`Plano
`Plano
`Plano
`
`Infinity
`-0.295
`0.544
`0.070
`O.300
`O408
`0.277
`O.86
`0.492
`0.100
`0.644
`OOO
`O.300
`0.975
`
`Fig.7
`
`Plastic
`
`544
`
`55.9
`
`3.85
`
`Plastic
`
`1.632
`
`23.4
`
`-8.18
`
`Plastic
`
`544
`
`55.9
`
`-97.98
`
`Plastic
`
`1544
`
`55.9
`
`7.29
`
`Plastic
`
`1.544
`
`55.9
`
`-9.2
`
`Glass
`
`1517
`
`64.2
`
`APPL-1008 / Page 8 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 8 of 13
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`US 8,233,224 B2
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`Surface #
`
`2
`
`TABLE 2
`Aspheric Coefficients
`3
`4.
`
`5
`
`6
`
`k =
`
`A4 =
`A6 =
`A8 =
`A 10=
`A12==
`A 14=
`A 16
`
`2.14772E-01 - 1.00000E-00 3.631.16E--04 8.10223E-00 - 1.00000E--00
`-1.31489E-02 -8.93237E-02 - 1.04367E-02 5. 70855E-02
`-10 1292E-01
`-147658E-02 2.0551 E-02 9.85 187E-02
`143963E-Ol
`-2.43027E-02
`-5.67815E-03 3.53580E-02
`-3.99988E-02 - 14282E-01
`8.3545 E-03
`2.5 1805E-03
`-383556E-O2 2.3340OE-02
`-2.21901 E-02
`
`1.01 047E-01
`
`- 19594OE-03
`-8.61299E-03
`180 139E-03
`
`-7.42997E-04
`
`Surface it
`
`7
`
`8
`
`9
`
`10
`
`R
`
`k
`A4 F
`A6 =
`A8 =
`
`A10s
`Al2=
`Al4 =
`
`
`-OOOOOE-00-100.000E-00-100000E-00-187192E-01 -9.57921 E-00
`-4.40404E-02.
`-3.40218E-02
`-7.4961 1 E-02 6.76904E-02 7.92341 E-02
`-2.73159E-02 -2.41658E-02 -2.37275E-02 5,54721E-03
`9.60671 E-03
`-3.22066E-04
`-2.0233E-03
`38402E-O2
`-5.78439E-03 5.08 192E-03
`-152799E-05
`2.30078E-04
`-9.93068E-06
`-2.91448E-07
`
`1.03756E-03
`-6.47005E-03 8.16669E-03
`-3.48727E-03 -4.41 16OE-04
`
`Fig.8
`
`APPL-1008 / Page 9 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 9 of 13
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`US 8,233,224 B2
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`TABLE 3
`(Embodiment 2)
`f = 5.46 mm, Fno - 2.9. HFOV = 33.0 deg.
`Curvature Radius Thickness Material
`Index
`
`Abbe if fG
`
`Surface #
`
`O
`
`2
`3
`4.
`5
`6
`7
`8
`9
`10
`11
`12
`13
`14
`
`Object
`Ape. Stop
`Lens 1
`
`Lens 2
`
`Lens 3
`
`Lens4
`
`LensS
`
`IR-filter
`
`Image
`
`Plano
`Plano
`1.63182 (ASP)
`6.51830 (ASP)
`100.00000 (ASP)
`4.54780 (ASP)
`2.62599 (ASP)
`2.71644 (ASP)
`-1.25296 (ASP)
`-1.19387 (ASP)
`2.85295 (ASP)
`1.92197 (ASP)
`Plano
`Plano
`Plano
`
`Infinity
`-0.251
`0.555
`0.070
`O.300
`0.4
`0.326
`0.817
`0.40
`0.00
`0.738
`1000
`0.300
`0.953
`
`Plastic
`
`1544
`
`55.9
`
`3.85
`
`Plastic
`
`1632
`
`23.4
`
`-755
`
`Plastic
`
`1.632
`
`23.4
`
`52.09
`
`Plastic
`
`1.544
`
`55.9
`
`13.72
`
`Plastic
`
`1544
`
`55.9
`
`-502
`
`Glass
`
`1517
`
`642
`
`Fig.9
`
`APPL-1008 / Page 10 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 10 of 13
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`US 8,233,224 B2
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`TABLE 4
`Aspheric Coefficients
`Surface it
`2
`3
`4
`5
`6
`k = 18352OE-01 - 1.0000 OE-00-100000E+00 1.75322E--01 - 1.00000E--00
`A4 = -2.19906E-02 -9.46773E-02 -2.351 68E-04 4.300.45E-02 -8.07699E-02
`A6 = -7.91364E-03 6.75602E-03 7.60931 E-02 8.85976E-02 -748881 E-03
`A8 = -3.74236E-02 2.76996E-03 -3.9723OE-02 -7.08086E-02 -2.20 195E-02
`A10= 158336E-02 - 123943E-02 2.93922E-02 2.61251 E-02 3.54907E-02
`A12 = -2.19436E-02
`-2.45503E-02
`Al4 =
`1.7143OE-03
`Al6 =
`-8.6l338E-04
`
`Surface #
`7
`8
`9
`10
`1
`k = -1.00000E--00-100.000E-HOO -1.00000E-00-157576E+01 - 1.16295E-01
`A4 = -5.94929E-02 143139E-01 12271 7E-01 -3.3903 E-02 -4.10434E-02
`A6 = -3.56226E-02 -4.97493E-02 - 162014E-02 103873E-02 9.7337OE-03
`A8 = 2.31795E-02 - 1.03685E-02 220416E-03 - 157303E-03 - 196225E-03
`A10= -1.05164E-02 1.15780E-02 -8.47082E-04 7, 18402E-05 2.28257E-04
`A 12-
`-381329E-03 8.10332E-05
`-1.25631 E-05
`A14=
`-14524 E-07
`
`Fig.10
`
`APPL-1008 / Page 11 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 11 of 13
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`US 8,233,224 B2
`
`TABLES
`(Embodiment 3)
`f = 5.47 mm, Fino - 2.90. HFOW - 33.0 deg.
`Curvature Radius Thickness Material
`Index
`
`Abbe it A.
`
`Surface #
`
`0
`1
`2
`3
`4
`5
`6
`7
`8
`9
`10
`11
`12
`13
`14
`
`Object
`Ape. Stop
`Lens 1
`
`Lens 2
`
`Lens 3
`
`Lens4
`
`Lens5
`
`IR-filter
`
`Image
`
`Plano
`Plano
`1.59122 (ASP)
`6.27730 (ASP)
`95.15520 (ASP)
`4.32910 (ASP)
`2.66560 (ASP)
`2.70650 (ASP)
`-1.28622 (ASP)
`-122799 (ASP)
`2.61083 (ASP)
`1.83624 (ASP)
`Plano
`Plano
`Plano
`
`Infinity
`-0.251
`0.554
`0.050
`0.300
`0.459
`0.327
`0.810
`0.395
`0.100
`0.733
`OOO
`0.300
`0.942
`
`Plastic
`
`544
`
`55.9
`
`3.76
`
`Plastic
`
`1632
`
`23.4
`
`-7.19
`
`Plastic
`
`632
`
`23.4
`
`68. 14
`
`Plastic
`
`1544
`
`55.9
`
`14.70
`
`Plastic
`
`1530
`
`55.8
`
`-17.37
`
`Glass
`
`157
`
`64.2
`
`Fig.11
`
`APPL-1008 / Page 12 of 21
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`U.S. Patent
`
`Jul. 31, 2012
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`Sheet 12 of 13
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`US 8,233,224 B2
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`Surface #
`
`2
`
`TABLE 6
`Aspheric Coefficients
`3
`4
`
`5
`
`6
`
`k = 2.09651E-01 - 100000E--00-100 OOOE-00 9.99772E-00 - 1.00000E--00
`A4 = -1.7793OE-02 -8.72936E-02 -9.52488E-04 4.97.902E-02 -8.71676E-02
`A6 = -1.49198E-02 1.18932E-02 8.64 198E-02 1.02616E-01 -1.22907E-02
`A8 = -2.16321E-02 2.19445E-02 - 197815E-02 -6.24973E-02 -2.13884E-02
`A10= 5.06499E-03 -3.50593E-02 7.13718E-03 3.79381 E-02 3.41 199E-02
`Al2 = -2.28246E-02
`-2.09784E-02
`Al4 =
`2.292.79E-03
`Al6 =
`-8.61.338E-04
`
`Surface #
`
`7
`
`8
`
`9
`
`10
`
`k = - 1.OOOOOE-00 - 1.OOOOOE-00 OOOOOE-00 - 1300SE--01 - 1.0574E--01
`A4 = -6.4819E-02 1595 12E-01 125998E-01 -3.70522E-02 -4.15102E-02
`A6 = -4.04836E-02 -5.1 1615E-02 - 1.57374E-02 .02084E-02 9.52140E-03
`A8 = 2.3 102E-02 - 19922E-02 .5724.6E-03 -1.26222E-03 - 193210E-03
`A10= -8.571 16E-03 123102E-02 - 1.30371E-03 2.99868E-05 2.22574E-04
`Al2=
`-4.30806E-03 1.9l832E-04
`-9.32854E-06
`A 14-
`-5.31861 E-07
`
`Fig. 12
`
`APPL-1008 / Page 13 of 21
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`U.S. Patent
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`Jul. 31, 2012
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`Sheet 13 of 13
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`US 8,233,224 B2
`
`TABLE 7
`Embodiment Embodiment Embodiment
`2
`3
`5.46
`5.47
`2.9
`2.9
`33.0
`33.0
`32.5
`32.5
`0.0
`0.0
`1.42
`1.45
`-0.91
`-0.85
`0.30
`0.29
`0.83
`0.79
`0.97
`0.98
`1.05
`1.05
`148
`142
`1.28
`0.91
`1.66
`1.66
`
`5.44
`2.9
`33.0
`32.5
`32.5
`141
`-0.79
`0.28
`0.93
`1.09
`1.27
`173
`129
`1.66
`
`f
`Fno
`HFOV
`V-V2
`V2-V3
`f/f
`fa/fs
`R/f
`R4/f
`Ro/Ri
`
`(T12/f)*100
`TTL/ImgH
`
`Fig.13
`
`APPL-1008 / Page 14 of 21
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`1.
`MAGING LENS SYSTEM
`
`US 8,233,224 B2
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to an imaging lens system,
`and more particularly, to an imaging lens system used in a
`mobile phone camera.
`2. Description of the Prior Art
`In recent years, with the popularity of mobile phone cam
`eras, the demand for compact imaging lenses is increasing,
`and the sensor of a general photographing camera is none
`other than CCD (charge coupled device) or CMOS device
`(Complementary Metal Oxide Semiconductor device). Fur
`thermore, as advanced semiconductor manufacturing tech
`nology has allowed the pixel size of sensors to be reduced and
`the resolution of compact imaging lenses has gradually
`increased, there is an increasing demand for compact imaging
`lenses featuring better image quality.
`A conventional compact lens assembly for mobile phone
`cameras, such as the four lens element assembly disclosed in
`U.S. Pat. No. 7.365,920, generally comprises four lens ele
`ments. However, the four-element lens has become insuffi
`cient for a high-end imaging lens assembly due to the rapid
`increase in the resolution of mobile phone cameras, the reduc
`tion in the pixel size of sensors and the increasing demand for
`compact lens assemblies featuring better image quality. As
`there is an ongoing trend toward compact yet powerful elec
`tronic products, a need exists in the art for an imaging lens
`system applicable to high-resolution mobile phone cameras
`while maintaining a moderate total track length.
`
`10
`
`15
`
`25
`
`30
`
`SUMMARY OF THE INVENTION
`
`The present invention provides an imaging lens system
`including, in order from the object side to the image side: a
`first lens element with positive refractive power having a
`convex object-side Surface; a second lens element with nega
`tive refractive power, a third lens element having a concave
`image-side Surface; a fourth lens element with positive refrac
`tive power; a fifth lens element with negative refractive power
`having a concave image-side Surface, at least one Surface
`thereof being provided with at least one inflection point; and
`an aperture stop disposed between an imaged object and the
`third lens element; wherein the on-axis spacing between the
`first lens element and the second lens element is T12, the focal
`length of the imaging lens system is f, and they satisfy the
`relation: 0.5<(T12/fx100<15.
`Such an arrangement of optical elements can effectively
`correct the aberrations to improve image quality of the sys
`tem, reduce the total track length of the imaging lens system
`and achieve a wide field of view.
`In the aforementioned imaging lens system, the first lens
`element provides a positive refractive power, and the aperture
`stop is disposed near the object side of the imaging lens
`system, thereby the total track length of the imaging lens
`system can be reduced effectively. The aforementioned
`arrangement also enables the exit pupil of the imaging lens
`system to be positioned far away from the image plane, thus
`light will be projected onto the electronic sensor at a nearly
`perpendicular angle, and this is the telecentric feature of the
`image side. The telecentric feature is very important to the
`photosensitive power of the current Solid-state sensor as it can
`improve the photosensitivity of the sensor to reduce the prob
`ability of the occurrence of shading. Moreover, the inflection
`point provided on the fifth lens element can effectively reduce
`the angle at which the light is projected onto the sensor from
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`the off-axis field so that the off-axis aberrations can be further
`corrected. In addition, when the aperture stop is disposed near
`the third lens element, a wide field of view can be favorably
`achieved. Such an aperture stop placement facilitates the
`correction of the distortion and chromatic aberration of mag
`nification, thereby the sensitivity of the imaging lens system
`can be effectively reduced. In other words, when the aperture
`stop is disposed near the imaged object, the telecentric feature
`is emphasized and enables a shorter total track length. When
`the aperture stop is disposed near the third lens element, the
`emphasis is on the wide field of view so that the sensitivity of
`the imaging lens system can be effectively reduced.
`The present invention provides another imaging lens sys
`tem including, in order from the object side to the image side:
`a first lens element with positive refractive power having a
`convex object-side Surface; a second lens element with nega
`tive refractive power; a third lens element with negative
`refractive power; a fourth lens element with positive refrac
`tive power having a concave object-side Surface and a convex
`image-side Surface; a fifth lens element with negative refrac
`tive power having a concave image-side Surface, at least one
`surface thereof being provided with at least one inflection
`point; and an aperture stop disposed between an imaged
`object and the third lens element; wherein the on-axis spacing
`between the first lens element and the second lens element is
`T12, the focal length of the imaging lens system is f, and they
`satisfy the relation: 0.5<(T12/f)x100<15.
`In the aforementioned imaging lens system, the third lens
`element has negative refractive power so that the Petzval Sum
`of the system can be effectively corrected, enabling the focal
`plane to become more flat near the periphery; the fourth lens
`element has a concave object-side Surface and a convex
`image-side Surface so that the astigmatism of the system can
`be effectively corrected. Moreover, when the aperture stop is
`disposed near the object side, the telecentric feature is empha
`sized and enables a shorter total track length. When the aper
`ture stop is disposed near the third lens element, the emphasis
`is on the wide field of view so that the sensitivity of the
`imaging lens system can be effectively reduced.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows an imaging lens system in accordance with a
`first embodiment of the present invention.
`FIG.2 shows the aberration curves of the first embodiment
`of the present invention.
`FIG.3 shows an imaging lens system in accordance with a
`second embodiment of the present invention.
`FIG. 4 shows the aberration curves of the second embodi
`ment of the present invention.
`FIG. 5 shows an imaging lens system in accordance with a
`third embodiment of the present invention.
`FIG. 6 shows the aberration curves of the third embodiment
`of the present invention.
`FIG. 7 is TABLE 1 which lists the optical data of the first
`embodiment.
`FIG. 8 is TABLE 2 which lists the aspheric surface data of
`the first embodiment.
`FIG.9 is TABLE3 which lists the optical data of the second
`embodiment.
`FIG.10 is TABLE 4 which lists the aspheric surface data of
`the second embodiment.
`FIG. 11 is TABLE5 which lists the optical data of the third
`embodiment.
`FIG. 12 is TABLE 6 which lists the aspheric surface data of
`the third embodiment.
`
`APPL-1008 / Page 15 of 21
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`US 8,233,224 B2
`
`3
`FIG. 13 is TABLE 7 which lists the data of the respective
`embodiments resulted from the equations.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`4
`first lens element is f1 and they preferably satisfy the relation:
`1.0<f7f131.8. When the above relation is satisfied, the refrac
`tive power of the first lens element is more balanced so that
`the total track length of the system can be effectively reduced.
`The above relation also prevents the high order spherical
`aberration from becoming too large, so that the image quality
`can be improved. And it will be more preferable that fand f1
`satisfy the relation: 1.2<f7f1<1.6.
`In the aforementioned imaging lens system, the focal
`length of the fourth lens element is fa, the focal length of the
`fifth lens element is f5, and they preferably satisfy the rela
`tion: -1.5<faffs.<-0.5. The above relation ensures the tele
`photo structure formed by the fourth and fifth lens elements
`and facilitates reducing the total track length of the system.
`In the aforementioned imaging lens system, it is preferable
`that, of the third, fourth and fifth lens elements, all lens
`elements which are meniscus in shape satisfy the relation:
`0.5<R/R,<2.0, wherein R represents the radius of curvature
`of the object-side surface of the meniscus lens element and R,
`represents the radius of curvature of the image-side Surface of
`the meniscus lens element. The above relation effectively
`reduces the sensitivity of the system by preventing the refrac
`tive power of the meniscus lens elements from becoming too
`large.
`In the aforementioned imaging lens system, the radius of
`curvature of the object-side surface of the first lens element is
`R1, the focal length of the imaging lens system is f, and they
`preferably satisfy the relation: 0.2<R1/f-0.4. When the above
`relation is satisfied, the total track length of the imaging lens
`system can be effectively reduced. The above relation also
`prevents the high order aberrations from becoming too large.
`In the aforementioned imaging lens system, the aperture
`stop is disposed between the imaged object and the first lens
`element so that the telecentric feature is emphasized, result
`ing in a shorter total track length.
`The aforementioned imaging lens system further com
`prises an electronic sensor on which an object is imaged. The
`on-axis spacing between the object-side Surface of the first
`lens element and the electronic sensor is TTL, half of the
`diagonal length of the effective pixel area of the electronic
`sensor is ImgH, and they preferably satisfy the relation: TTL/
`ImgH-2.0. The above relation enables the imaging lens sys
`tem to maintain a compact form so that it can be equipped in
`compact portable electronic products.
`In the aforementioned imaging lens system, the radius of
`curvature of the image-side surface of the second lens ele
`ment is R4, the focal length of the imaging lens system is f.
`and they preferably satisfy the relation: 0.7<R4/f-1.2. When
`the above relation is satisfied, the chromatic aberration of the
`system can be effectively corrected. The above relation also
`prevents the back focal length of the imaging lens system
`from becoming too long so that the system can maintain a
`compact form.
`In the aforementioned imaging lens system, the Abbe num
`ber of the second lens element is V2, the Abbe number of the
`third lens element is V3, and they preferably satisfy the rela
`tion: V2-V3|<15, thereby the chromatic aberration of the
`system can be effectively corrected.
`The present invention provides another imaging lens sys
`tem including, in order from the object side to the image side:
`a first lens element with positive refractive power having a
`convex object-side Surface; a second lens element with nega
`tive refractive power; a third lens element with negative
`refractive power; a fourth lens element with positive refrac
`tive power having a concave object-side Surface and a convex
`image-side Surface; a fifth lens element with negative refrac
`tive power having a concave image-side Surface, at least one
`
`The present invention provides an imaging lens system
`including, in order from the object side to the image side: a
`first lens element with positive refractive power having a
`convex object-side Surface; a second lens element with nega
`tive refractive power, a third lens element having a concave
`image-side Surface; a fourth lens element with positive refrac
`tive power; a fifth lens element with negative refractive power
`having a concave image-side Surface, at least one Surface
`thereof being provided with at least one inflection point; and
`an aperture stop disposed between an imaged object and the
`third lens element; wherein the on-axis spacing between the
`first lens element and the second lens element is T12, the focal
`length of the imaging lens system is f, and they satisfy the
`relation: 0.5<(T12/f)x100<15.
`In the aforementioned imaging lens system, the first lens
`element has positive refractive power and a convex object
`side Surface so that the total track length of the imaging lens
`system can be effectively reduced; the second lens element
`has negative refractive power so that the chromatic aberration
`of the system can be favorably corrected; the third lens ele
`ment may be a lens element with either negative or positive
`refractive power; the fourth lens element has positive refrac
`tive power so that the positive refractive power of the first lens
`element can be effectively distributed to reduce the sensitivity
`of the imaging lens system; the fifth lens element with nega
`tive refractive power and the fourthlens element with positive
`refractive powerform a telephoto structure, thereby the total
`track length of the imaging lens system can be effectively
`reduced. When the third lens element has negative refractive
`power, the Petzval Sum of the system can be more effectively
`corrected, enabling the focal plane to become more flat near
`the periphery. When the third lens element has positive refrac
`tive power, the high order aberrations of the system can be
`favorably corrected.
`In the aforementioned imaging lens system, the on-axis
`spacing between the first lens element and the second lens
`element is T12, the focal length of the imaging lens system is
`f, and they satisfy the relation: 0.5<(T12/f)x100<15. The
`above relation can prevent the astigmatism from becoming
`too large.
`In the aforementioned imaging lens system, it is preferable
`that the second lens element has a concave image-side Surface
`so as to effectively lengthen the back focal length of the
`imaging lens system, thereby providing sufficient space
`between the fifth lens element and the image plane to accom
`modate other components.
`In the aforementioned imaging lens system, it is preferable
`that the third lens element has a convex object-side surface so
`that the high order aberrations of the system can be favorably
`corrected to improve the image quality. Preferably, the fourth
`lens element has a concave object-side Surface and a convex
`image-side Surface so that the astigmatism of the system can
`be effectively corrected.
`In the aforementioned imaging lens system, the Abbenum
`ber of the first lens element is V1, the Abbe number of the
`second lens element is V2, and they preferably satisfy the
`relation: V1-V2>20, thereby the chromatic aberration can be
`effectively corrected. And it will be more preferable that V1
`and V2 satisfy the relation: V1-V2>30.
`In the aforementioned imaging lens system, the focal
`length of the imaging lens system is f, the focal length of the
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`5
`surface thereof being provided with at least one inflection
`point; and an aperture stop disposed between an imaged
`object and the third lens element; wherein the on-axis spacing
`between the first lens element and the second lens element is
`T12, the focal length of the imaging lens system is f, and they
`satisfy the relation: 0.5<(T12/f)x100<15.
`In the aforementioned imaging lens system, the first lens
`element has positive refractive power and a convex object
`side Surface so that the total track length of the imaging lens
`system can be effectively reduced; the second lens element
`has negative refractive power so that the chromatic aberration
`of the system can be favorably corrected; the third lens ele
`ment has negative refractive power so that the Petzval Sum of
`the system can be more effectively corrected, enabling the
`focal plane to become more flat near the periphery; the fourth
`lens element has positive refractive power so that the positive
`refractive power of the first lens element can be effectively
`distributed to reduce the sensitivity of the imaging lens sys
`tem, and the concave object-side surface and the convex
`image-side surface thereof facilitate the correction of the
`astigmatism of the system; the fifth lens element with nega
`tive refractive power and the fourth lens element with positive
`refractive powerform a telephoto structure, thereby the total
`track length of the imaging lens system can be effectively
`reduced.
`In the aforementioned imaging lens system, the on-axis
`spacing between the first lens element and the second lens
`element is T12, the focal length of the imaging lens system is
`f, and they satisfy the relation: 0.5<(T12/f)x100<15. The
`above relation can prevent the astigmatism from becoming
`too large.
`In the aforementioned imaging lens system, it is preferable
`that the second lens element has a concave image-side Surface
`so as to effectively lengthen the back focal length of the
`imaging lens system, thereby providing sufficient space
`between the fifth lens element and the image plane to accom
`modate other components.
`In the aforementioned imaging lens system, it is preferable
`that the third lens element has a convex object-side surface
`and a concave image-side surface so that the high order aber
`rations of the system can be favorably corrected to improve
`the image quality.
`In the aforementioned imaging lens system, the Abbenum
`ber of the first lens element is V1, the Abbe number of the
`second lens element is V2, and they preferably satisfy the
`relation: V1-V2>30, thereby the chromatic aberration can be
`effectively corrected.
`In the aforementioned imaging lens system, the focal
`length of the imaging lens system is f, the focal length of the
`first lens element is f1, and they preferably satisfy the relation:
`1.0<f7f131.8. When the above relation is satisfied, the refrac
`tive power of the first lens element is more balanced so that
`the total track length of the system can be effectively reduced.
`The above relation also prevents the high order spherical
`aberration from becoming too large, so that the image quality
`can be improved. And it will be more preferable that fand f1
`satisfy the relation: 1.2<f/fl-1.6.
`In the aforementioned imaging lens system, the focal
`length of the fourth lens element is fa, the focal length of the
`fifth lens element is f5, and they preferably satisfy the rela
`tion: -1.5<faffs.<-0.5. The above relation ensures the tele
`photo structure formed by the fourth and fifth lens elements
`and facilitates reducing the total track length of the system.
`In the aforementioned imaging lens system, it is preferable
`that, of the third, fourth and fifth lens elements, all lens
`elements which are meniscus in shape satisfy the relation:
`0.5<R/R,<2.0, wherein R represents the radius of curvature
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`US 8,233,224 B2
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`of the object-side surface of the meniscus lens element and R,
`represents the radius of curvature of the image-side Surface of
`the meniscus lens element. The above relation effectively
`reduces the sensitivity of the system by preventing the refrac
`tive power of the meniscus lens elements from becoming too
`large.
`In the aforementioned imaging lens system, the radius of
`curvature of the object-side surface of the first lens element is
`R1, the focal length of the imaging lens system is f, and they
`preferably satisfy the relation: 0.2<R1/f-0.4. When the above
`relation is satisfied, the total track length of the imaging lens
`system can be effectively reduced. The above relation also
`prevents the high order aberrations from becoming too large.
`In the aforementioned imaging lens system, the aperture
`stop is disposed between the imaged object and the first lens
`element so that the telecentric feature is emphasized, result
`ing in a shorter total track length.
`The aforementioned imaging lens system further com
`prises an electronic sensor on which an object is imaged. The
`on-axis spacing between the object-side Surface of the first
`lens element and the electronic sensor is TTL, half of the
`diagonal length of the effective pixel area of the electronic
`sensor is ImgH, and they preferably satisfy the relation: TTL/
`ImgH-2.0. The above relation enables the imaging lens sys
`tem to maintain a compact form so that it can be equipped in
`compact portable electronic products.
`In the present imaging lens system, the lens elements can
`be made of glass or plastic material. If the lens elements are
`made of glass, there is more freedom in distributing the
`refractive power of the system. If plastic material is adopted
`to produce lens elements, the production cost will be reduced
`effectively. Additionally, the surfaces of the lens elements can
`be aspheric and easily made into non-spherical profiles,
`allowing more design parameter freedom which can be used
`to reduce aberrations and the number of the lens elements, so
`that the total track length of the imaging lens system can be
`reduced effectively.
`In the present imaging lens system, if a lens element has a
`convex surface, it means the portion of the Surface proximate
`to the axis is convex; if a lens element has a concave surface,
`it means the portion of the Surface proximate to the axis is
`COCaV.
`Preferred embodiments of the present invention will be
`described in the following paragraphs by referring to the
`accompanying drawings.
`FIG. 1 shows an imaging lens system in accordance with a
`first embodiment of the present invention, and FIG. 2 shows
`the aberration curves of the first embodiment of the present
`invention. The imaging lens system of the first embodiment of
`the present invention mainly comprises five lens elements
`including, in order from the object side to the image side: a
`plastic first lens element 100 with positive refractive power
`having a convex object-side Surface 101 and a concave image
`side surface 102, the object-side and image-side surfaces 101
`and 102 thereof being aspheric; a plastic second lens element
`110 with negative refractive power having a convex object
`side Surface 111 and a concave image-side Surface 112, the
`object-side and image-side surfaces 111 and 112 thereof
`being aspheric; a plastic third lens element 120 with negative
`refractive power having a convex object-side Surface 121 and
`a concave image-side Surface 122, the object-side and image
`side surfaces 121 and 122 thereof being aspheric; a plastic
`fourth lens element 130 with positive refractive power having
`a concave object-side Surface 131 and a convex image-side
`surface 132, the object-side and image-side surfaces 131 and
`132 thereof being aspheric; and a plastic fifth lens element
`140 with negative refractive power having a convex object
`
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`US 8,233,224 B2
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`7
`side Surface 141 and a concave image-side Surface 142, the
`object-side and image-side surfaces 141 and 142 thereof
`being aspheric, and each of which being provided with at least
`one inflection point; wherein an aperture stop 150 is disposed
`between an imaged object and the first lens element 100:
`wherein the imaging lens system further comprises an IR
`filter 160 disposed between the image-side surface 142 of the
`fifth lens element 140 and the image plane 170; and wherein
`the IR filter 160 has no influence on the focal length of the
`imaging lens System.
`The equation of the aspheric Surface profiles is expressed
`as follows:
`
`5
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`first lens element 100 is R1, the focal len