(12) United States Patent
`Ogino et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9,128.267 B2
`Sep. 8, 2015
`
`US009 128267B2
`
`(54) IMAGING LENS AND IMAGINGAPPARATUS
`INCLUDING THE MAGING LENS
`
`(71) Applicant: FUJIFILM Corporation, Tokyo (JP)
`
`(72) Inventors: Tatsuyuki Ogino, Saitama-ken (JP);
`Michio Cho, Saitama-ken (JP); Yoshiaki
`Ishii, Saitama-ken (JP)
`
`(73) Assignee: FUJIFILM CORPORATON, Tokyo
`(JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 14/226,172
`ppl. No.:
`9
`
`(22) Filed:
`(65)
`
`• 1-1 s 1-
`
`u -
`
`Mar. 26, 2014
`Prior Publication Data
`f
`US 2014/O293453 A1
`Oct. 2, 2014
`O
`O
`Foreign Application Priority Data
`(30)
`Mar. 29, 2013 (JP)
`2013-072282
`(51) Int. Cl.
`GO2B 3/02
`GO2B I3/00
`(52) U.S. Cl.
`CPC .................................. G02B 13/0045 (2013.01)
`
`way - F
`
`· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
`
`(2006.01)
`(2006.01)
`
`(58) Field of Classification Search
`CPC ................................................... GO2B 13 FOO45
`USPC .......................................................... 3597714
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`M
`8,310,768 B2 11/2012 Lin et al.
`2010, O253829 A1* 10, 2010 Shinohara ......
`2012/0087020 A1* 4/2012 Tang et al. ...
`2013, OO33765 A1
`2/2013 Tsai et al.
`* cited by examiner
`
`... 348/340
`359,714
`
`Primary Examiner —James Jones
`(74) Attorney, Agent, or Firm — Young & Thompson
`57
`ABSTRACT
`(
`An imaging lens Substantially consists of, in order from an
`object side, five lenses of a first lens that has a positive
`refractive power and has a meniscus shape which is convex
`toward the object side, a second lens that has a biconcave
`shape, a third lens that has a meniscus shape which is convex
`toward the object side, a fourth lens that has a meniscus shape
`which is convex toward the image side; and a fifth lens that
`point on an image side Surface. Further, the following condi
`tional expression (1) is satisfied.
`1.4<ffl<4
`
`has a negative refractive power and has at least one inflection
`
`(1)
`
`21 Claims, 14 Drawing Sheets
`
`CG
`
`EXAMPE
`
`5
`
`4.
`
`St1
`
`.
`
`St2(R3)
`"
`| 2
`|
`
`L3
`
`
`
`
`
`--.100(R14)
`
`APPL-1005 / Page 1 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 1 of 14
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`US 9,128.267 B2
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`FIG.1
`
`
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`EXAMPLE 1.
`
`--..100(R14)
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`APPL-1005 / Page 2 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 2 of 14
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`US 9,128.267 B2
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`FIG.2
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`
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`EXAMPLE 2
`
`-100(R14)
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`APPL-1005 / Page 3 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 3 of 14
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`US 9,128.267 B2
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`
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`FIG.3
`
`EXAMPLE 3
`
`- 100(R14)
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`APPL-1005 / Page 4 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 4 of 14
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`US 9,128.267 B2
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`FIG.4
`
`EXAMPLE 4
`
`
`
`--...100(R14)
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`APPL-1005 / Page 5 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 5 of 14
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`US 9,128.267 B2
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`FIG.5
`
`EXAMPLE 5.
`
`
`
`D13
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`-100(R14)
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`APPL-1005 / Page 6 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 6 of 14
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`US 9,128.267 B2
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`FIG.6
`
`EXAMPLE 6
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`
`
`---.100(R4)
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`APPL-1005 / Page 7 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 7 of 14
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`US 9,128.267 B2
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`FIG.7
`
`EXAMPLE
`
`
`
`-...-100
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`APPL-1005 / Page 8 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 8 of 14
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`US 9,128.267 B2
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`APPL-1005 / Page 9 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 9 of 14
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`US 9,128.267 B2
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`HNIT-p–
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`% 0 | -
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`APPL-1005 / Page 10 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 10 of 14
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`% 0 | -
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`
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`Uu?? 00||O UU 77 00 | -
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 11 of 14
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`US 9,128.267 B2
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`% 0 | -
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`Lu 77 00||O UUTÍ OO|-
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 12 of 14
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`APPL-1005 / Page 14 of 28
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`U.S. Patent
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`Sep. 8, 2015
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`Sheet 14 of 14
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`2
`The imaging lens of the present invention is an imaging
`lens Substantially consisting of, in order from an object side,
`five lenses of:
`a first lens that has a positive refractive power and has a
`meniscus shape which is convex toward the object side;
`a second lens that has a biconcave shape;
`a third lens that has a meniscus shape which is convex
`toward the object side;
`a fourth lens that has a meniscus shape which is convex
`toward an image side; and
`a fifth lens that has a negative refractive power and has at
`least one inflection point on an image side Surface,
`in which the following conditional expression (1) is satis
`fied:
`
`(1), where
`
`1.4<fflk4
`f is a focal length of a whole system, and
`fl is a focal length of the first lens.
`According to the imaging lens of the present invention, in
`the imaging lens which is composed offive lenses as a whole,
`a configuration of each lens element of the first to fifth lenses
`is optimized. Therefore, it is possible to achieve a lens system
`that has high resolution performance while decreasing the
`total length thereof.
`In the imaging lens of the present invention, the expression
`“Substantially consisting of five lenses' means that the imag
`ing lens of the present invention may include not only the five
`lenses but also a lens which has substantially no refractive
`power, optical elements, such as a stop and a cover glass,
`which are not a lens, mechanism parts, such as a lens flange,
`a lens barrel, an imaging device and a hand shake blur cor
`rection mechanism, and the like. When the lens includes an
`aspheric Surface, the reference sign of the Surface shape and
`refractive power of the lens is considered in a paraxial region.
`In the imaging lens of the present invention, by employing
`and satisfying the following desirable configuration, it is pos
`sible to make the optical performance thereof better.
`In the imaging lens of the present invention, it is desirable
`that the fourth lens have a positive refractive power.
`It is desirable that the imaging lens of the present invention
`further include an aperture stop that is disposed on the object
`side of an object side surface of the second lens.
`It is desirable that the imaging lens of the present invention
`satisfy any of the following conditional expressions (1-1) to
`(10). It should be noted that, as a desirable mode, any one of
`the conditional expressions (1-1) to (10) may be satisfied, or
`an arbitrary combination thereof may be satisfied. However,
`regarding the conditional expression (7-1), when the compos
`ite refractive power of the first to third lenses is positive, it is
`desirable to satisfy the conditional expression (7-1).
`1.5<fflk3.5
`
`(1-1),
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`US 9,128.267 B2
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`1.
`IMAGING LENS AND MAGINGAPPARATUS
`INCLUDING THE MAGING LENS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a fixed-focus imaging lens
`that forms an optical image of a Subject on an imaging device,
`Such as a charge coupled device (CCD) and a complementary
`metal oxide semiconductor(CMOS), and to an imaging appa
`ratus, Such as a digital still camera, a cellular phone with a
`camera, a mobile information terminal (PDA: Personal Digi
`tal Assistance), a Smartphone, a tablet terminal, and a mobile
`game machine, on which the imaging lens is mounted to
`perform photography.
`2. Description of the Related Art
`As personal computers have become popular in homes,
`digital still cameras which are capable of inputting image
`information about photographed scenes, persons, and the like
`into the personal computers have spread rapidly. Further, a
`cellular phone, a Smartphone, or a tablet terminal in which a
`camera module for inputting images is installed has been
`increasing. Such apparatus having an imaging function uses
`an imaging device, such as a CCD and a CMOS. Recently,
`because the imaging device has been miniaturized, there has
`been also a demand to miniaturize the whole of the imaging
`apparatus and an imaging lens mounted thereon. Further,
`since the number of pixels included in the imaging device has
`also been increasing, there has been a demand to enhance the
`resolution and performance of the imaging lens. For example,
`there has been a demand for performance corresponding to
`high resolution of 5 megapixels or higher, and preferably
`performance corresponding to high resolution of 8 megapix
`els or higher.
`To satisfy Such demands, it can be considered that the
`imaging lens is composed of five or six lenses, which are a
`relatively large number of lenses. For example, U.S. Pat. No.
`8.310,768 (Patent Document 1) and U.S. Patent Application
`Publication No. 20130033765 (Patent Document 2) propose
`an imaging lens composed of five lenses. The imaging lens
`disclosed in Patent Documents 1 and 2 substantially consists
`of in order from an object side, five lenses of a first lens that
`has a positive refractive power, a second lens that has a nega
`tive refractive power, a third lens that has a positive refractive
`power, a fourth lens that has a positive refractive power, and
`a fifth lens that has a negative refractive power.
`
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`SUMMARY OF THE INVENTION
`
`50
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`In particular, for the imaging lenses used in apparatuses, of
`which the thickness has been decreased. Such as a cellular
`phone, a Smartphone or a tablet terminal, a demand to
`decrease the total length of the lens has been increased more
`and more. Hence, it is necessary to further decrease the total
`lengths of the imaging lenses disclosed in Patent Documents
`1 and 2.
`The present invention has been made in view of the above
`mentioned circumstances and an object thereof is to provide
`an imaging lens capable of achieving high imaging perfor
`mance in the range from the central angle of view to the
`peripheral angle of view while achieving a decrease in the
`total length thereof. Another object of the present invention is
`to provide an imaging apparatus capable of obtaining a pho
`tographed image with high resolution through the imaging
`lens which is mounted thereon.
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`US 9,128.267 B2
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`3
`
`4
`FIG. 4 is a lens cross-sectional view illustrating a fourth
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 4;
`FIG. 5 is a lens cross-sectional view illustrating a fifth
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 5:
`FIG. 6 is a lens cross-sectional view illustrating a sixth
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 6:
`FIG. 7 is a ray diagram of the imaging lens shown in FIG.
`1;
`FIG. 8 is an aberration diagram illustrating various aberra
`tions of animaging lens according to Example 1 of the present
`invention, where Section A shows a spherical aberration,
`Section B shows astigmatism (curvature of field), Section C
`shows distortion, and Section D shows a lateral chromatic
`aberration;
`FIG. 9 is an aberration diagram illustrating various aberra
`tions of animaging lens according to Example 2 of the present
`invention, where Section A shows a spherical aberration,
`Section B shows astigmatism (curvature of field), Section C
`shows distortion, and Section D shows a lateral chromatic
`aberration;
`FIG. 10 is an aberration diagram illustrating various aber
`rations of an imaging lens according to Example 3 of the
`present invention, where Section. A shows a spherical aberra
`tion, Section B shows astigmatism (curvature of field), Sec
`tion C shows distortion, and Section D shows a lateral chro
`matic aberration:
`FIG. 11 is an aberration diagram illustrating various aber
`rations of an imaging lens according to Example 4 of the
`present invention, where Section. A shows a spherical aberra
`tion, Section B shows astigmatism (curvature of field), Sec
`tion C shows distortion, and Section D shows a lateral chro
`matic aberration;
`FIG. 12 is an aberration diagram illustrating various aber
`rations of an imaging lens according to Example 5 of the
`present invention, where Section. A shows a spherical aberra
`tion, Section B shows astigmatism (curvature of field), Sec
`tion C shows distortion, and Section D shows a lateral chro
`matic aberration;
`FIG. 13 is an aberration diagram illustrating various aber
`rations of an imaging lens according to Example 6 of the
`present invention, where Section. A shows a spherical aberra
`tion, Section B shows astigmatism (curvature of field), Sec
`tion C shows distortion, and Section D shows a lateral chro
`matic aberration;
`FIG. 14 is a diagram illustrating an imaging apparatus
`which is a cellular phone terminal including the imaging lens
`according to the present invention; and
`FIG. 15 is a diagram illustrating an imaging apparatus
`which is a Smartphone including the imaging lens according
`to the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Hereinafter, embodiments of the present invention will be
`described in detail with reference to the accompanying draw
`1ngS.
`FIG. 1 shows a first configuration example of an imaging
`lens according to a first embodiment of the present invention.
`The configuration example corresponds to a lens configura
`tion of a first numerical value example (Table 1 and Table 2)
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`(10), where
`
`0.05<D7/f-0.2
`fis a focal length of a whole system,
`fl is a focal length of the first lens,
`f2 is a focal length of the second lens,
`f3 is a focal length of the third lens,
`f5 is a focal length of the fifth lens,
`fl2 is a composite focal length of the first lens and the
`second lens,
`f345 is a composite focal length of the third to fifth lenses,
`R3f is a paraxial radius of curvature of an object side
`surface of the third lens,
`R3r is a paraxial radius of curvature of an image side
`surface of the third lens,
`R5r is a paraxial radius of curvature of an image side
`surface of the fifth lens,
`D7 is a spacing on an optical axis between the third lens and
`the fourth lens, and
`() is a half angle of view.
`The imaging apparatus of the present invention includes
`the imaging lens of the present invention.
`In the imaging apparatus of the present invention, imaging
`signals with high resolution can be obtained based on an
`optical image with high resolution obtained by the imaging
`lens of the present invention.
`According to the imaging lens of the present invention, in
`the imaging lens which is composed offive lenses as a whole,
`a configuration of each lens element is optimized, and par
`ticularly the shapes of the first and fifth lenses are appropri
`ately formed. Therefore, it is possible to achieve a lens system
`that has high resolution performance in the range from the
`central angle of view to the peripheral angle of view while
`decreasing the total length thereof.
`Further, according to the imaging apparatus of the present
`invention, imaging signals based on an optical image formed
`by the imaging lens of the present invention, which has high
`imaging performance, are output. Therefore, it is possible to
`obtain a photographed image with high resolution.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a lens cross-sectional view illustrating a first
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 1:
`FIG. 2 is a lens cross-sectional view illustrating a second
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 2:
`FIG. 3 is a lens cross-sectional view illustrating a third
`configuration example of an imaging lens according to an
`embodiment of the present invention and corresponding to
`Example 3:
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`5
`to be described later. Likewise, FIGS. 2 to 6 show cross
`sections of second to sixth configuration examples corre
`sponding to the imaging lenses according to second to sixth
`embodiments to be described later. The second to sixth con
`figuration examples correspond to lens configurations of the
`second to sixth numerical value examples (Tables 3 to 12) to
`be described later. In FIGS. 1 to 6, the reference sign Ri
`represents a radius of curvature of i-th surface, where the
`number i is the sequential number that sequentially increases
`as it gets closer to an image side (an imaging side) when a
`Surface of a lens element closest to an object side is regarded
`as a first Surface. The reference sign Direpresents an on-axis
`Surface spacing between i-th Surface and (i+1) th Surface on
`an optical axis Z1. Since the respective configuration
`examples are basically similar in configuration, the following
`description will be given on the basis of the first configuration
`example of the imaging lens shown in FIG. 1, and the con
`figuration examples shown in FIGS. 2 to 6 will be also
`described as necessary. Further, FIG. 7 is an optical path
`diagram of the imaging lens L shown in FIG. 1, and shows an
`optical path of rays 2 on the optical axis from an object point
`at the infinite distance and an optical path of rays 3 at the
`maximum angle of view.
`An imaging lens L according to an embodiment of the
`present invention is appropriate to be used in various kinds of
`imaging apparatuses using imaging devices such as a CCD
`and a CMOS. Especially, the imaging lens L is appropriate to
`be used in relatively small-sized mobile terminal apparatus,
`for example, such as a digital still camera, a cellular phone
`with a camera, a Smartphone, a tablet terminal, and a PDA.
`This imaging lens L includes, along the optical axis Z1, a first
`lens L1, a second lens L2, a third lens L3, a fourth lens L4, and
`a fifth lens L5 in this order from the object side.
`FIG. 14 is a schematic diagram illustrating a cellular phone
`terminal, which is an imaging apparatus 1 according to an
`embodiment of the present invention. The imaging apparatus
`1 according to the embodiment of the present invention
`includes imaging lens L according to the present embodiment
`and an imaging device 100 (refer to FIG. 1), such as a CCD,
`which outputs imaging signals based on an optical image
`formed by the imaging lens L. The imaging device 100 is
`disposed at an image formation Surface (image plane R14) of
`the imaging lens L.
`FIG. 15 is a schematic diagram illustrating a Smartphone
`which is an imaging apparatus 501 according to an embodi
`ment of the present invention. The imaging apparatus 501
`according to the embodiment of the present invention
`includes a camera unit 541 including the imaging lens L
`according to the present embodiment and the imaging device
`100 (refer to FIG. 1), such as a CCD, which outputs imaging
`signals based on an optical image formed by the imaging lens
`L. The imaging device 100 is disposed at the image formation
`Surface (image plane R14) of the imaging lens L.
`Various optical members CG may be disposed between the
`fifth lens L5 and the imaging device 100 based on the con
`figuration of a camera on which the imaging lens is mounted.
`For example, a flat-plate-shaped optical member, Such as a
`coverglass for protecting an imaging Surface and an infrared
`ray cut filter, may be disposed. In this case, for example, a
`flat-plate-shaped cover glass to which a coating having an
`effect of a filter, such as an infrared-ray cut filter and an ND
`filter, has been applied, or a material having the same effect
`may be used as the optical member CG.
`Alternatively, an effect similar to the optical member CG
`may be given to the fifth lens L5 or the like by applying a
`coating to the fifth lens L5 or the like without using the optical
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`member CG. Thereby, it is possible to reduce the number of
`components, and to reduce the total length.
`Further, it is desirable that the imaging lens L includes an
`aperture stop St disposed on the object side of an object side
`surface of the second lens L2. Since the aperture stop St is
`disposed on the object side of the object side surface of the
`second lens L2 in Such a manner, especially in a peripheral
`portion of an imaging area, it is possible to prevent an angle of
`incidence of rays, which pass through the optical system and
`are incident onto an imaging Surface (imaging device), from
`becoming large. In order to further enhance this effect, it is
`more desirable that the aperture stop St be disposed on the
`object side of an object side surface of the first lens L1. Here,
`the expression “disposed on the object side of the object side
`surface of the second lens L2 means that the position of the
`aperture stop in the optical axis direction is the same as an
`intersection point between an on-axis marginal ray and the
`object side surface of the second lens L2 or located on the
`object side of the intersection point. Likewise, the expression
`“disposed on the object side of an object side surface of the
`first lens L1 means that the position of the aperture stop in
`the optical axis direction is the same as an intersection point
`between an on-axis marginal ray and the object side Surface of
`the first lens L1 or located on the object side of the intersec
`tion point.
`In the embodiments of the present invention, the imaging
`lenses of the third and sixth configuration examples (refer to
`FIGS. 3 and 6) are configuration examples in which the aper
`ture stop St is disposed on the object side of the object side
`Surface of the first lens L1, and the imaging lenses of the first,
`second, fourth and fifth configuration examples (refer to
`FIGS. 1, 2, 4 and 5) are configuration examples in which the
`aperture stop St is disposed on the object side of the object
`side surface of the second lens L2. It should be noted that the
`aperture stop St shown herein does not necessarily represent
`the size or shape thereof but shows the position thereof on the
`optical axis Z1.
`When the aperture stop St is disposed on the object side of
`the object side surface of the second lens L2, a flare stop for
`Suppressing a flare component or a ghost component may be
`further provided on the object side of the object side surface
`of the first lens L1. In the embodiments of the present inven
`tion, lenses as first and second configuration examples (FIGS.
`1 and 2) are configuration examples in which the flare stop is
`provided. It should be noted that, in FIGS. 1 and 2, the flare
`stop is referenced by the reference sign St1, and the aperture
`stop is referenced by the reference sign St2. In this case, the
`aperture stop St2 is a stop that restricts an F-number, and the
`flare stop St1 is a stop that restricts rays at peripheral angles of
`view.
`Furthermore, when the aperture stop St is disposed on the
`object side of the object side surface of the first lens L1 in the
`optical axis, it is desirable that the aperture stop St be dis
`posed on the image side of a vertex of the surface of the first
`lens L1. When the aperture stop St is disposed on the image
`side of the vertex of the surface of the first lens L1 in such a
`manner, it is possible to reduce the total length of the imaging
`lens including the aperture stop St. In the above-mentioned
`embodiments, the aperture stop St is disposed on the image
`side of the vertex of the surface of the first lens L1. However,
`the invention is not limited to the embodiments, and the
`aperture stop St may be disposed on the object side of the
`vertex of the surface of the first lens L1. The arrangement, in
`which the aperture stop Stis disposed on the object side of the
`vertex of the surface of the first lens L1, is slightly disadvan
`tageous in terms of securing a peripheral light amount, com
`pared with a case where the aperture stop Stis disposed on the
`
`APPL-1005 / Page 18 of 28
`APPLE INC. v. COREPHOTONICS LTD.
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`7
`image side of the vertex of the surface of the first lens L1.
`However, the arrangement can prevent an angle of incidence
`of rays, which pass through the optical system and are inci
`dent onto the imaging Surface (imaging device), from becom
`ing large in the peripheral portion of the imaging area in a
`more desirable manner.
`As in the imaging lenses according to the first, second,
`fourth and fifth embodiments shown in FIGS. 1, 2, 4 and 5, the
`aperture stop St (St2) may be disposed between the first lens
`L1 and the second lens L2 in the optical axis direction. In this
`case, it is possible to satisfactorily correct a curvature of field.
`When the aperture stop St is disposed between the first lens
`L1 and the second lens L2 in the optical axis direction, as
`compared with a case where the aperture stop St is disposed
`on the object side of the object side surface of the first lens L1
`in the optical axis direction, this arrangement is disadvanta
`geous in securing telecentricity, that is, making the principal
`rays parallel to Such an extent that the principal rays are
`regarded as the optical axis (setting an incident angle thereof
`on the imaging Surface Such that the angle is approximate to
`Zero). Thus, by applying an imaging device which is recently
`implemented as the development in the imaging device tech
`nology advances and in which deterioration in the light
`receiving efficiency and occurrence of color mixture due to
`increase of incident angle are more reduced than in the con
`ventional imaging device, it is possible to achieve optimum
`optical performance.
`In the imaging lens L, the first lens L1 has a positive
`refractive power in the vicinity of the optical axis, and has a
`meniscus shape which is convex toward the object side in the
`vicinity of the optical axis. As shown in the embodiments, by
`making the first lens L1, which is a lens closest to the object,
`have a positive refractive power and have a meniscus shape
`which is convex toward the object side in the vicinity of the
`optical axis, the position of the rear side principal point of the
`first lens L1 can be set to be close to the object, and thus it is
`possible to appropriately reduce the total length.
`The second lens L2 has a biconcave shape in the vicinity of
`the optical axis. Thereby, it is possible to appropriately Sup
`press occurrence of a high-order spherical aberration while
`satisfactorily correcting a chromatic aberration, and it is also
`possible to appropriately reduce the total length.
`The third lens L3 has a meniscus shape which is convex
`toward the object side in the vicinity of the optical axis.
`Thereby, the position of the rear side principal point of the
`third lens L3 can be more appropriately set to be close to the
`object side, and thus it is possible to appropriately reduce the
`total length. As long as the third lens L3 has a meniscus shape
`which is convex toward the object side in the vicinity of the
`optical axis, it is possible to adopt a configuration in which the
`50
`third lens L3 has a positive refractive power in the vicinity of
`the optical axis, and it is also possible to adopt a configuration
`in which the third lens L3 has a negative refractive power in
`the vicinity of the optical axis. As in the imaging lenses
`according to the first to third embodiments shown in FIGS. 1
`to 3, when the third lens L3 is configured to have a positive
`refractive power in the vicinity of the optical axis, it is pos
`sible to more appropriately reduce the totallength. Further, as
`in the imaging lenses according to the fourth to sixth embodi
`ments shown in FIGS. 4 to 6, when the third lens L3 is
`configured to have a negative refractive power in the vicinity
`of the optical axis, it is possible to more satisfactorily correct
`a chromatic aberration.
`The fourth lens L4 has a meniscus shape which is convex
`toward the image side in the vicinity of the optical axis.
`Thereby, it is possible to appropriately correctastigmatism. It
`is desirable that the fourth lens L4 have a positive refractive
`
`8
`power in the vicinity of the optical axis. Thereby, especially at
`the medium angle of view, it is possible to prevent the angle of
`incidence of rays, which pass through the optical system and
`are incident onto the image formation Surface (imaging
`device), from becoming large, and thus it is possible to satis
`factorily correct a lateral chromatic aberration while appro
`priately reducing the total length.
`The fifth lens L5 has a negative refractive power in the
`vicinity of the optical axis. A lens, which has a negative
`refractive power in the vicinity of the optical axis, is disposed
`to be closest to the image side of the imaging lens, whereby
`the imaging lens can be more appropriately made to have a
`telephototype configuration as a whole, and thus it is possible
`to appropriately reduce the total length. In addition, since the
`fifth lens L5 has a negative refractive power in the vicinity of
`the optical axis, it is possible to appropriately correct a cur
`Vature of field. When the fifth lens L5 is concave toward the
`image side in the vicinity of the optical axis, it is possible to
`satisfactorily correct a curvature of field while more appro
`priately reducing the total length. In order to further enhance
`this effect, as shown in the first, second, and sixth embodi
`ments, it is desirable that the fifth lens L5 have a meniscus
`shape which is concave toward the image side in the vicinity
`of the optical axis.
`The fifth lens L5 has at least one inflection point within an
`effective diameter of the image side surface. The “inflection
`point’ on the image side surface of the fifth lens L5 is defined
`as a point at which the shape of the image side Surface of the
`fifth lens L5 changes from a convex shape to a concave shape
`(or from a concave shape to a convex shape) toward the image
`side. The inflection point can be disposed at an arbitrary
`position on the outside in a radial direction from the optical
`axis as long as the point is within the effective diameter of the
`image side surface of the fifth lens L5. As shown in the
`respective embodiments, by forming the image side Surface
`of the fifth lens L5 in a shape in which the image side surface
`has at least one inflection point, especially in a peripheral
`portion of an image formation area, it is possible to prevent
`the angle of incidence of rays, which pass through the optical
`system and are incident onto the image formation Surface
`(imaging device), from becoming large.
`According to the imaging lens L, in the imaging lens which
`is composed offive lenses as a whole, a configuration of each
`lens element of the first to fifth lenses L1 to L5 is optimized.
`Therefore, it is possible to achieve a lens system that has high
`resolution performance while decreasing the total length
`thereof.
`In the imaging lens L, in order to enhance the performance
`thereof, it is desirable that at least one surface of each lens of
`the first to fifth lenses L1 to L5 be formed as an aspheric
`Surface.
`Further, it is desirable that each of the lenses L1 to L5
`constituting the imaging lens L be not formed as a cemented
`lens but a single lens. The reason is that, compared with a case
`where any of the lenses L1 to L5 is formed as a cemented lens,
`since the number of aspheric Surfaces increases, a degree of
`freedom in design of each lens is enhanced, and it is possible
`to appropriately achieve reduction in the total length thereof.
`Next, effects and advantages of the conditional expressions
`of the imaging lens L configured as described above will be
`described in detail.
`First, it is desirable that the focal length fl of the first lens
`L1 and the focal length f of the whole system satisfy the
`following conditional expression (1).
`
`1.4<fflk4
`
`(1)
`
`US 9,128.267 B2
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`55
`
`60
`
`65
`
`APPL-1005 / Page 19 of 28
`APPLE INC. v. COREPHOTONICS LTD.
`
`

`

`The conditional expression (1) defines a desirable numeri
`cal range of a ratio of the focal length fof the whole system to
`the focal leng