WO2019119312A1 - Optical system, camera module and electronic apparatus - Google Patents

Optical system, camera module and electronic apparatus Download PDF

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Publication number
WO2019119312A1
WO2019119312A1 PCT/CN2017/117535 CN2017117535W WO2019119312A1 WO 2019119312 A1 WO2019119312 A1 WO 2019119312A1 CN 2017117535 W CN2017117535 W CN 2017117535W WO 2019119312 A1 WO2019119312 A1 WO 2019119312A1
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WIPO (PCT)
Prior art keywords
lens element
optical system
satisfied
image
following conditional
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PCT/CN2017/117535
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French (fr)
Inventor
Tateoka SUSUMU
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Huawei Technologies Co., Ltd.
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Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to PCT/CN2017/117535 priority Critical patent/WO2019119312A1/en
Publication of WO2019119312A1 publication Critical patent/WO2019119312A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
    • G02B13/0045—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having five or more lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/62—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having six components only

Definitions

  • the present invention relates to an optical system, a camera module and an electronic apparatus.
  • an image sensor and an optical system including at least one lens may be mounted.
  • performance of the optical system is decreased. Therefore, optical systems with greater performance are desired.
  • an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element having a convex object-side surface at least in a paraxial region and a concave image-side surface at least in a paraxial region, a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof; wherein the following conditional expressions are satisfied: 0 ⁇ f2/f1 ⁇ 15.0; and 0 ⁇ (f/f1) / ( (f/f2) + (f/f4) ) ⁇ 5.0, where f is a focal
  • an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element having a convex object-side surface at least in a paraxial region; a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a paraxial regionl region thereof; wherein the following conditional expressions are satisfied: 0 ⁇ f2/f1 ⁇ 15; 0 ⁇ (f/f1) (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) ⁇ 8.0; and 0.5 ⁇ f/R7 ⁇ 20.0 where
  • an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element; a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power having a concave image-side surface at least in a paraxial region, wherein the image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof; wherein the following conditional expressions are satisfied:
  • f1 is a focal length of the first lens element
  • f2 is a focal length of the second lens element
  • f4 is a focal length of the fourth lens element
  • f5 is a focal length of the fifth lens element
  • Fno is an f-number of the optical system.
  • a camera module comprising: the optical system of any one of the above embodiments; and an image sensor.
  • an electronic apparatus comprising: the camera module of the above embodiment; a display section; and a control section that controls the camera module and the display section.
  • FIG. 1 is a block diagram of the electronic apparatus according to the present embodiment.
  • FIG. 2 is a schematic view of the optical device according to the present embodiment, along with the paths of a plurality of light rays.
  • FIG. 3 shows the field curvature of the optical device.
  • FIG. 4 shows the distortion of the optical device.
  • FIG. 5 shows a spot diagram of the optical device.
  • FIG. 6 shows an OTF curve of the optical device.
  • FIG. 1 is a block diagram of an electronic apparatus 100 according to the present embodiment.
  • the electronic apparatus 100 is a mobile device, such as a smart phone, a mobile telephone, a tablet computer or a camera.
  • the electronic apparatus 100 may have a thin housing (not shown) .
  • the electronic apparatus 100 includes a camera module 1, a display section 101, a wireless communication section 102, an user interface 103 and a control section 104.
  • the wireless communication section 102 and the user interface 103 do not need to be included in the electronic apparatus 100.
  • the camera module 1 images an object.
  • the camera module 1 may be mounted in the thin housing, such that an optical axis of the camera module 1 is parallel to a thickness direction of the thin housing.
  • the camera module 1 may generate image data and supply it to at least one of the display section 101, the wireless communication section 102 and a storage section (not shown) .
  • the display section 101 displays the image data.
  • the display section 101 may display character data and operational buttons that are manipulated by a user.
  • the wireless communication section 102 may transmits and receives information using wireless communication such as wireless telecommunication network, wireless LAN (Local Area Network) , BlueTooth, or infrared communication. As an example, the wireless communication section 102 may transmit the image data to another electronic apparatus.
  • wireless communication such as wireless telecommunication network, wireless LAN (Local Area Network) , BlueTooth, or infrared communication.
  • the wireless communication section 102 may transmit the image data to another electronic apparatus.
  • the user interface 103 receives manipulation input from the user.
  • the user interface 103 may be formed integrally with the display section 101.
  • the control section 104 may perform overall control of the electronic apparatus 100.
  • the control section 104 controls imaging by the camera module 1.
  • FIG. 2 is a schematic view of the camera module 1 according to the present embodiment, along with the paths of a plurality of light rays.
  • the camera module 1 includes an optical system 2 and an image sensor 3.
  • the optical system 2 forms an image of an object.
  • the optical system 2 includes, in order from an object side to an image side, an aperture stop 20, a first lens element 21, a second lens element 22, a third lens element 23, a fourth lens element 24, a fifth lens element 25, a sixth lens element 26, and an IR cut filter 29.
  • the aperture stop 20 and the IR cut filter 29 do not need to be included in the optical system 2.
  • the optical system 2 may further include other optical elements, such as a mirror and/or prism, for example.
  • the aperture stop 20 is a front stop which can be disposed between the object and the first lens element 21.
  • the aperture stop 20 provides a longer distance from an exit pupil of the optical system 2 to an image plane, and therefore the generated telecentric effect improves the image-sensing efficiency of the image sensor 3.
  • the optical system 2 may include one or more aperture stops that are middle stops.
  • the middle stop is disposed between the first lens element 21 and the image plane.
  • the field of view of the optical system 2 can be larger.
  • the optical system 2 may include other types of stops, such as a flare stop or a field stop.
  • the flare stop and the field stop may be allocated to reduce stray light while retaining high image quality.
  • the first lens element 21 (also referred to as the lens element 21) has positive refractive power.
  • the first lens element 21 has an object-side surface 21a and an image-side surface 21b.
  • the object-side surface 21a is convex at least in a paraxial region.
  • the image-side surface 21b may be concave at least in a paraxial region. Therefore, the total track length of the optical system 2 can be reduced by adjusting the positive refractive power of the first lens element 21.
  • the object-side surface 21a and/or the image-side surface 21b may be aspheric.
  • an optical surface may have a paraxial region and a peripheral region.
  • the paraxial region refers to a region of the optical surface where light rays travel close to an optical axis.
  • the peripheral region refers to a region of the optical surface where light rays travel away from the optical axis. If a lens element has a convex surface at least in the paraxial region, i.e. if the optical surface is convex at least in theparaxial region, it may indicate that the peripheral region may be other shape, such as concave or flat. If the lens element has a concave surface at least in the paraxial region, i.e. if the optical surface is concave at least in the paraxial region, it may indicate that the peripheral region may be other shape, such as convex or flat.
  • the second lens element 22 (also referred to as the lens element 22) has positive refractive power.
  • the second lens element 22 has an object-side surface 22a and an image-side surface 22b.
  • the image-side surface 22b may be convex at least in a paraxial region, so that the positive refractive power of the first lens element 21 can be balanced for avoiding the excessive distribution of refractive power from the first lens element 21. Therefore, the spherical aberration of the optical system 2 can be corrected.
  • the object-side surface 22a may also be convex.
  • the object-side surface 22a and/or the image-side surface 22b may be aspheric.
  • the third lens element 23 (also referred to as the lens element 23) has negative refractive power.
  • the third lens element 23 has an object-side surface 23a and an image-side surface 23b.
  • the image-side surface 23b may be concave at least in a paraxial region, so that the aberration generated from the first lens element 21 and the second lens element 22 can be reduced.
  • the object-side surface 23a may be convex at least in a paraxial region.
  • the object-side surface 23a and/or the image-side surface 23b may be aspheric.
  • the fourth lens element 24 (also referred to as the lens element 24) may have positive refractive power.
  • the fourth lens element 24 has an object-side surface 24a and an image-side surface 24b.
  • the object-side surface 24a may be convex at least in a paraxial region and the image-side surface 24b may be concave at least in a paraxial region, so that the astigmatism of the optical system 2 can be corrected.
  • the object-side surface 24a and/or the image-side surface 24b may be aspheric.
  • the object-side surface 24a may change from convex at a paraxial region thereof to concave at a peripheral region thereof, and the image-side surface 24b may change from concave at a paraxial region thereof to convex at a peripheral region thereof. Therefore, the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected.
  • the fifth lens element 25 (also referred to as the lens element 25) has positive refractive power.
  • the fifth lens element 25 has an object-side surface 25a and an image-side surface 25b.
  • the object-side surface 25a may be concave and the image-side surface 25b is convex. Therefore, the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality.
  • the object-side surface 25a and/or the image-side surface 25b may be aspheric.
  • the sixth lens element 26 (also referred to as the lens element 26) has negative refractive power.
  • the sixth lens element 26 has an object-side surface 26a and an image-side surface 26b.
  • the image-side surface 26b is concave at least in a paraxial region. Therefore, the principal point of the optical system 2 can be positioned away from the image plane.
  • the optical path length, the back focal length, and the size of the optical system 2 can be reduced.
  • the image-side surface 26b is at least partially aspheric.
  • the image-side surface 26b changes from concave at a paraxial region thereof to convex at a peripheral region thereof.
  • the object-side surface 26a may also be concave.
  • the object-side surface 26a may be at least partially aspheric.
  • the IR cut filter 29 may be made of infrared absorption ink over a substrate.
  • the substrate may be made of plastic material or glass material.
  • a glass substrate with a thickness of 0.11 mm made of borosilicate glass can be used as the substrate.
  • the IR cut filter 29 does not affect the focal length of the optical system 2.
  • f1 is a focal length of the first lens element 21
  • f2 is a focal length of the second lens element 22.
  • the lower limit value of Expression 1 may be 0.2, 0.25, 0.4, 0.5 or 1.0.
  • the upper limit value of Expression 1 may be 10.0, 5.0, 4.8, 2.0 or 1.0.
  • Expression 1 may be 0 ⁇ f2/f1 ⁇ 10.0, 0 ⁇ f2/f1 ⁇ 2.0, 0 ⁇ f2/f1 ⁇ 5.0, 0.2 ⁇ f2/f1 ⁇ 5.0, 0.5 ⁇ f2/f1 ⁇ 5.0 or 1.0 ⁇ f2/f1 ⁇ 10.
  • f is a focal length of the optical system 2.
  • f may be between 2.16 mm and 3.28 mm.
  • f4 is a focal length of the fourth lens element 24.
  • the telephoto functionality of the optical system 2 can be enhanced to reduce the back focal length and the total track length of the optical system 2, so that the optical system 2 can be applied to compact and portable electronics.
  • Expression 2 may be satisfied when the refractive power of the second lens element 22 and the fourth lens element 24 is small, the refractive power of the first lens element 21 is large.
  • the refractive power of the second lens element 22 may be larger than the refractive power of the fourth lens element 24.
  • Focal lengths of the third lens element 23 and the fifth lens element 25 may be designed to have larger aspherical coefficiencies so that an F-number and back focus of the optical system 2 are maintained.
  • the lower limit value of Expression 2 may be 0.2 or 0.35.
  • the upper limit value of Expression 2 may be 3.0, 2.0, 1.0 or 0.75.
  • Expression 2 may be 0 ⁇ (f/f1) / ( (f/f2) + (f/f4) ) ⁇ 3.0, 0 ⁇ (f/f1) / ( (f/f2) + (f/f4) ) ⁇ 2.0 or 0 ⁇ (f/f1) / ( (f/f2) + (f/f4) ) ⁇ 1.0.
  • f3 is a focal length of the third lens element 23
  • f5 is a focal length of the fifth lens element 25
  • f6 is a focal length of the sixth lens element 26.
  • the portion surrounded by the inequality signs may express a Petzval sum of the optical system 2, and may relate to astigmatism of the optical system 2. Since the Petzval sum is less than 1.0, the astigmatism of the optical system 2 is small and the MTF (Modulated Transfer Function) is favorable.
  • Expression 3 and/or Expression 3”’are satisfied, the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected.
  • the upper limit value of Expression 3” may be 2.0.
  • the lower limit value of Expression 4 may be -0.25 or -0.2.
  • the upper limit value of Expression 4 may be 0.75, 0.5, or 0.45.
  • Expression 4 may be -0.5 ⁇ f/f4 ⁇ 0.75 or -0.25 ⁇ f/f4 ⁇ 1.5.
  • f/f4 may be 0.05.
  • V1 is an Abbe number of the first lens element 21
  • V3 is an Abbe number of the third lens element 23.
  • the lower limit value of Expression 5 may be 0.2, 0.25 or 0.3.
  • the upper limit value of expression 5 may be 0.5 or 0.35.
  • expression 5 may be 0.2 ⁇ V3/V1 ⁇ 0.35 or 0.3 ⁇ V3/V1 ⁇ 0.5.
  • V1 may be 53.0
  • V3 may be 20.4, and V3/V1 may be 0.384.
  • R7 is a curvature radius of the object-side surface 24a of the fourth lens element 24.
  • the lower limit value of Expression 6 may be 0.5, 0.6, 0.8, 1.0, or 1.5.
  • the upper limit value of Expression 6 may be 10.0, 3.2, 3.0, 2.4, 2.2, or 1.65.
  • Expression 6 may be 0.2 ⁇ f/R7 ⁇ 20.0, 0.2 ⁇ f/R7 ⁇ 10.0, 0.5 ⁇ f/R7 ⁇ 20.0, 1 ⁇ f/R7 ⁇ 3.2, 1 ⁇ f/R7 ⁇ 3.0, or 1.5 ⁇ f/R7 ⁇ 1.65.
  • R3 is a curvature radius of the object-side surface 22a of the second lens element 22
  • R4 is a curvature radius of the image-side surface 22b of the second lens element 22.
  • the lower limit value of Expression 7 may be -0.4, -0.2, or 0.25.
  • the upper limit value of Expression 7 may be 0.55, 0.5, or 0.4.
  • Expression 7 may be -0.5 ⁇ (R3+R4) / (R3-R4) ⁇ 0.55, -0.5 ⁇ (R3+R4) / (R3-R4) ⁇ 0.5, -0.4 ⁇ (R3+R4) / (R3-R4) ⁇ 0.55, or 0.25 ⁇ (R3+R4) / (R3-R4) ⁇ 0.75.
  • T23 is an axial distance between the second lens element 22 and the third lens element 23.
  • ET23 is a distance in parallel with an optical axis between a maximum effective diameter position on the image-side surface 22b of the second lens element 22 and a maximum effective diameter position on the object-side surface 23a of the third lens element 23.
  • T34 is an axial distance between the third lens element 23 and the fourth lens element 24.
  • ET34 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface 23b of the third lens element 23 and a maximum effective diameter position on an object-side surface 24a of the fourth lens element 24.
  • the yield rate of assembling the optical system 2 can be increased by properly arranging thickness of the lens elements 22, 23 and the distance between them and/or thickness of the lens elements 23, 24 and the distance between them, in order to avoid interference of the lens elements. Moreover, distortion of the optical system 2 can be balanced between the lens elements 21 to 26 and can be reduced in total.
  • the upper limit value of Expression 8 may be 0.45, 0.30, or 0.20.
  • Expression 8 may be 0 ⁇ T23/ET23 ⁇ 0.45 or 0 ⁇ T23/ET23 ⁇ 0.20.
  • T12 is an axial distance between the first lens element 21 and the second lens element 22.
  • T45 is an axial distance between the fourth lens element 24 and the fifth lens element 25.
  • the lower limit value of Expression 9 may be 0.15 or 0.25.
  • the upper limit value of Expression 9 may be 0.35.
  • Expression 9 may be 0.15 ⁇ (T12+T23) / (T34+T45) ⁇ 0.35.
  • CT2 is a central thickness of the second lens element 22.
  • CT3 is a central thickness of the third lens element 23.
  • CT4 is a central thickness of the fourth lens element 24.
  • CT5 is a central thickness of the fifth lens element 25.
  • a lens element with a thickness that is too large or too small would be poorly fabricated and/or easily broken. Therefore, the yield rate of the lens elements 22 to 25 can be increased by properly setting the thicknesses of these lens elements.
  • the image-side lens elements, such as the lens elements 21 and 22, can be thick than the object-side lens elements, such as the lens elements 23 to 26, when two or three of Expressions 10-12 are satisfied.
  • the lower limit value of Expression 10 may be 0.2.
  • the upper limit value of Expression 11 may be 0.5.
  • Fno is an f-number of the optical system 2, which may be a ratio of focal length to an aperture of the optical system 2.
  • Fno may be between 2.0 and 2.2.
  • the optical system 2 can have a large aperture, so that the optical system 2 can capture clear images by a high-speed shutter in a low light environment along with a longer depth of field.
  • the lower limit value of Expression 13 may be 1.5 or 1.6.
  • the upper limit value of Expression 13 may be 2.8, 2.5, 2.2, or 2.0.
  • expression 13 may be 1.25 ⁇ Fno ⁇ 2.5, 1.5 ⁇ Fno ⁇ 2.5, or 1.5 ⁇ Fno ⁇ 2.8.
  • the TTL (through the lens) of the optical system 2 may be 4.5 mm, and the FOV (field of view) of the optical system 2 may be between 75 and 78 degrees.
  • the HFOV (half of the maximal field of view) may be 37.5 degrees.
  • the image sensor 3 may be a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) sensor.
  • the image sensor 3 may be a 1/3.2 type, and the effective size may be 4.5 mm ⁇ 3.4 mm.
  • the single pixel size of the image sensor 3 may be a small size such as 1.12 um, 1.0 um, or 0.9 um.
  • the image sensor 3 may be disposed on the image plane of the optical system 2.
  • the image sensor 3 may be operable to be moved by an anti-shaking correction mechanism. As an example, the image sensor 3 may be operable to move in the direction of the optical axis of the optical system 2, or may be operable to move in one or two directions orthogonal to the optical axis.
  • the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced.
  • the second lens element 22 haspositive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected.
  • the third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced.
  • the fourth lens element 24 has a convex object-side surface 24a at least in a paraxial region and a concave image-side 24b surface at least in a paraxial region, and therefore the astigmatism of the optical system 2 can be corrected.
  • the fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected to enhance the resolving power and the image quality.
  • the image-side surface 26b of the sixth lens element 26 changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected.
  • the conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced.
  • the conditional Expression 2 is satisfied, and therefore the telephoto functionality of the optical system 2 can be enhanced to reduce the back focal length and the total track length of the optical system 2, so that the optical system 2 can be applied to compact and portable electronics. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
  • the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced.
  • the second lens element 22 has positive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected.
  • the third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced.
  • the fourth lens element 24 has a convex object-side surface 24a at least in a paraxial region and a concave image-side 24b surface at least in a paraxial region, and therefore the astigmatism of the optical system 2 can be corrected.
  • the fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality.
  • the image-side surface 26b of the sixth lens element 26 changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected.
  • the conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced.
  • conditional Expression 3 is satisfied, and therefore the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected.
  • conditional expression 5 is satisfied, and therefore the sensitivity of the optical system 2 can be reduced effectively by properly adjusting the curvature of the object-side surface 24a of the fourth lens element 24. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
  • the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced.
  • the second lens element 22 has positive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected.
  • the third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced.
  • the fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality.
  • the six lens element 26 has a concave image-side surface 26b at least in a paraxial region, and the image-side surface 26b changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected.
  • the conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced.
  • the conditional Expression 3”’ is satisfied, and therefore the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected.
  • the conditional expression 13 is satisfied, and therefore the optical system 2 can capture clear images by a high-speed shutter at the low light environment along with a longer depth of field. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
  • the lens elements 21 to 26 can be made of glass material or plastic material independently.
  • the distribution of the refractive power of the optical system 2 may be more flexible to design.
  • the TTL (through the lens) and aberration including chromatic aberration of the optical system 2 can be reduced.
  • the manufacturing costs can be effectively reduced.
  • the optical surfaces can be made aspheric easily. As a result, more controllable variables are obtained, and the aberration of the optical system 2 can be reduced while maintainingthe number of lens elements. Therefore, by using both of glass material and plastic material, the total track length of the optical system 2 can also be reduced.
  • two of the lens elements 21 to 26 may be made of glass material and the remaining four lens elements may be formed of plastic material.
  • the first lens element 21 and the fifth lens element 25 may be made of glass material.
  • the second lens element 22, the third lens element 23, the fourth lens element 24 and the sixth lens element 26 may be made of plastic material.
  • the first lens element 21 and the fourth lens element 24 may be made of glass material.
  • the second lens element 22, the third lens element 23, the fifth lens element 25 and the sixth lens element 26 may be made of plastic material.
  • the lens material may be selected from materials having dimensional stability, molding easiness, high refractive index and/or high Abbe number.
  • commercially available low dispersion glass can be used as the glass material.
  • the plastic material may be a material for which Nd (the refractive index with respect to the d line) is 1.66 and vd (Abbe number) is 20.4, or a material for which Nd is 1.55 and vd is 53.0.
  • Commercially available cyclo-olefin polymer resin or commercially available polycarbonate resin can be used as the plastic material.
  • the first column indicates the object-side and image-side optical surfaces 21a to 26b of the optical elements 21 to 26.
  • the optical surfaces “29a” and “29b” are the object-side and image-side optical surfaces of the IR cut filter 29.
  • the second column indicates the shape of the optical surface.
  • “Standard” indicates a planar surface
  • “Even Aspheric” indicates a flat aspherical surface.
  • 16M (1/3.2) indicates that the image sensor 3 is a 1/3.2 type with 16 megapixels.
  • the fourth column indicates the curvature radius.
  • the fifth column indicates the distance between surfaces.
  • the sixth column indicates the refractive index with respect to the d line and the Abbe number.
  • the seventh column indicates the radius, and the eighth column (Conic) indicates the conic coefficient.
  • Table 2 shows another embodiment example of the camera module 1 according to the present embodiment.
  • the camera module 1 may satisfy the values shown in Table 2.
  • the aspheric surface profiles (sag quantities) of the lens elements 21 to 26 are expressed by the following Expression 20.
  • C is the curvature of the surface
  • k is the conic constant
  • r is the distance from the point on the optical surface to the optical axis in radial direction
  • a i is the aspheric coefficient.
  • i may be either an even number or an odd number
  • N may be approximately 240.
  • Table 3 shows the aspheric coefficient A i of each optical surface.
  • the first column indicates the object-side and image-side optical surfaces 21a to 26b of the optical elements 21 to 26 and the object-side and image-side optical surfaces 29a and 29b of the IR cut filter 29.
  • the second and following columns indicate the aspherical surface coefficient of each order.
  • FIG. 3 shows the field curvature of the camera module 1.
  • the vertical axis indicates the height from the optical axis
  • the horizontal axis indicates the magnitude of the field curvature.
  • Graph S shows the field curvature at the sagittal surface
  • Graph T shows the field curvature at the tangential surface (meridional surface) .
  • FIG. 4 shows the distortion of the camera module 1.
  • the vertical axis indicates the ideal image height
  • the horizontal axis indicates the magnitude of the distortion, i.e. the amount of skew of the actual height of the image relative to the ideal height of the image.
  • FIG. 5 shows spot diagrams of the camera module 1.
  • the upper left diagram shows the spot diagram in a case where the position of the image sensor is the best focused position and the light rays from the object form an angle of 0° with the optical axis.
  • the upper right diagram shows the spot diagram in a case where the position of the image sensor is shifted by 1.097 mm on the optical axis and the light rays from the object form an angle of 20° with the optical axis.
  • the points plotted in this figure respectively indicate focal positions of light rays with wavelengths of 0.5461, 0.5876, 0.4861, 0.4358, and 0.6563 (nm) .
  • FIG. 6 shows the OTF curve of the camera module 1.
  • the horizontal axis indicates the spatial frequency and the vertical axis indicates the resolution ratio.
  • Each graph shows the OTF curve of sagittal light rays and tangential light rays forming angles of 0, 10, 20, 30, 35, 40, and 45 (degrees) relative to the optical axis at the image plane.
  • the image sensor 3 is described as being moved by the anti-shaking correction mechanism. Instead of this, at least one of the lens elements 21 to 26 in the optical system 2 may be moved. Furthermore, the image sensor 3 and at least one of the lens elements 21 to 26 in the optical system 2 may be moved by a zoom mechanism and/or focus mechanism, which are not shown in the figures.
  • the camera module 1 is described as including the image sensor 3. However, if the image sensor 3 is detachable to the camera module 1, the image sensor 3 does not need to be equipped in the camera module 1.
  • the electronic apparatus 100 is described as a movile device.
  • the electronic apparatus 100 may be an on-vehicle camera, a robot eye, a security apparatus or an unmanned aircraft, such as a drone.
  • the embodiments of the present invention can be used to realize an optical system and a device that realizes higher performance capabilities while preventing an increase in size.

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Abstract

Provided is an optical system (2) comprising, in order from an object side to an image side: a first lens element (21) with positive refractive power having a convex object-side surface (21a) at least in a paraxial region; a second lens element (22) with positive refractive power; a third lens element (23) with negative refractive power; a fourth lens element (24) having a convex object-side surface (24a) at least in a paraxial region and a concave image-side surface (24b) at least in a paraxial region, a fifth lens element (25) with positive refractive power having a convex image-side surface (25b) at least in a paraxial region; and a sixth lens element (26) with negative refractive power, having a concave image-side surface (26b) at least in a paraxial region; wherein the following conditional expressions are satisfied: 0<f2/f1<15.0; and 0< (f/f1) / ((f/f2) + (f/f4)) <5.0, where f is a focal length of the optical system (2), f1 is a focal length of the first lens element (21), f2 is a focal length of the second lens element (22), and f4 is a focal length of the fourth lens element (24).

Description

OPTICAL SYSTEM, CAMERA MODULE AND ELECTRONIC APPARATUS BACKGROUND
1. TECHNICAL FIELD
The present invention relates to an optical system, a camera module and an electronic apparatus.
2. RELATED ART
In an apparatus capable of imaging an object, an image sensor and an optical system including at least one lens may be mounted. In recent years, since the apparatus and the optical system are made smaller, performance of the optical system is decreased. Therefore, optical systems with greater performance are desired.
SUMMARY
In one embodiment, provided is an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element having a convex object-side surface at least in a paraxial region and a concave image-side surface at least in a paraxial region, a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof; wherein the following conditional expressions are satisfied: 0<f2/f1<15.0; and 0< (f/f1) / ( (f/f2) + (f/f4) ) <5.0, where f is a focal length of the optical system, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, and f4 is a focal length of the fourth lens element.
In another embodiment, provided is an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element having a convex object-side surface at least in a paraxial region; a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a paraxial regionl region thereof; wherein the following conditional expressions are satisfied: 0<f2/f1<15; 0< (f/f1) (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) <8.0; and 0.5<f/R7<20.0 where f is a focal length of the optical system is f, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, f3 is a focal length of the third lens element, f4 is a focal length of the fourth lens element, f5 is a focal length of the fifth lens element, and R7 is a curvature radius of the object-side surface of the fourth lens element.
In still another embodiment, provided is an optical system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object side surface at least in a paraxial region; a second lens element with positive refractive power; a third lens element with negative refractive power; a fourth lens element; a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and a sixth lens element with negative refractive power having a concave image-side surface at least in a paraxial region, wherein the image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof; wherein the following conditional expressions are satisfied:
0<f2/f1<15.0; 0< (f/f1) / ( (f/f2) (f5) + (f/f4) ) <2.0; and 0.5<Fno<3.0 where f is a focal length of the optical system, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, f4 is a focal length of the fourth lens element, f5 is a focal length of the fifth lens element, and Fno is an f-number of the optical system.
With any one of the optical systems described above, it is possible to increase performance while preventing an increase in size.
In still another embodiment, provided is a camera module comprising: the optical system of any one of the above embodiments; and an image sensor. In still another embodiment, provided is an electronic apparatus comprising: the camera module of the above embodiment; a display section; and a control section that controls the camera module and the display section.
The summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The present invention may also be a sub-combination of the features described above. The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the electronic apparatus according to the present embodiment.
FIG. 2 is a schematic view of the optical device according to the present embodiment, along with the paths of a plurality of light rays.
FIG. 3 shows the field curvature of the optical device.
FIG. 4 shows the distortion of the optical device.
FIG. 5 shows a spot diagram of the optical device.
FIG. 6 shows an OTF curve of the optical device.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
Hereinafter, some embodiments of the present invention will be described. The embodiments do not limit the invention according to the claims, and all the combinations of the features described in the embodiments are not necessarily essential to means provided by aspects of the invention.
FIG. 1 is a block diagram of an electronic apparatus 100 according to the present embodiment. As an example in the present embodiment, the electronic apparatus 100 is a mobile device, such as a smart phone, a mobile telephone, a tablet computer or a camera. The electronic apparatus 100 may have a thin housing (not shown) .
The electronic apparatus 100 includes a camera module 1, a display section 101, a wireless communication section 102, an user interface 103 and a control section 104. The wireless communication section 102 and the user interface 103 do not need to be included in the electronic apparatus 100.
The camera module 1 images an object. The camera module 1 may be mounted in the thin housing, such that an optical axis of the camera module 1 is parallel to a thickness direction of the thin housing. The camera module 1 may generate image data and supply it to at least one of the display section 101, the wireless communication section 102 and a storage section (not shown) .
The display section 101 displays the image data. The display section 101 may display character data and operational buttons that are manipulated by a user.
The wireless communication section 102 may transmits and receives information using wireless communication such as wireless telecommunication network, wireless LAN (Local Area Network) , BlueTooth, or infrared communication. As an example, the wireless communication section 102 may transmit the image data to another electronic apparatus.
The user interface 103 receives manipulation input from the user. The user interface 103 may be formed integrally with the display section 101.
The control section 104 may perform overall control of the electronic apparatus 100. For example, the control section 104 controls imaging by the camera module 1.
FIG. 2 is a schematic view of the camera module 1 according to the present embodiment, along with the paths of a plurality of light rays. The camera module 1 includes an optical system 2 and an image sensor 3.
(1. The optical system 2)
The optical system 2 forms an image of an object. The optical system 2 includes, in order from an object side to an image side, an aperture stop 20, a first lens element 21, a second lens element 22, a third lens element 23, a fourth lens element 24, a fifth lens element 25, a sixth lens element 26, and an IR cut filter 29. The aperture stop 20 and the IR cut filter 29 do not need to be included in the optical system 2. The optical system 2 may further include other optical elements, such as a mirror and/or prism, for example.
(1-1. The aperture stop 20)
The aperture stop 20 is a front stop which can be disposed between the object and the first lens element 21. The aperture stop 20 provides a longer distance from an exit pupil of the optical system 2 to an image plane, and therefore the generated telecentric effect improves the image-sensing efficiency of the image sensor 3.
Instead of or in addition to the aperture stop 20, the optical system 2 may include one or more aperture stops that are middle stops. The middle stop is disposed between the first lens element 21 and the image plane. In this case, the field of view of the optical system 2 can be larger. The optical system 2 may include other types of stops, such as a flare stop or a field stop. The flare stop and the field stop may be allocated to reduce stray light while retaining high image quality.
(1-2. The first lens element 21)
The first lens element 21 (also referred to as the lens element 21) has positive refractive power. The first lens element 21 has an object-side surface 21a and an image-side surface 21b. The object-side surface 21a is convex at least in a paraxial region. The image-side surface 21b may be concave at least in a paraxial region. Therefore, the total track length of the optical system 2 can be reduced by adjusting the positive refractive power of the first lens element 21. The object-side surface 21a and/or the image-side surface 21b may be aspheric.
Here, an optical surface may have a paraxial region and a peripheral region. The paraxial region refers to a region of the optical surface where light rays travel close to an optical axis. The peripheral region refers to a region of the optical surface where light rays travel away from the optical axis. If a lens element has a convex surface at least in the paraxial region, i.e. if the optical surface is convex at least in theparaxial region, it may indicate that the peripheral region may be other shape, such as concave or flat. If the lens element has a concave surface at least in the paraxial region, i.e. if the optical surface is concave at least in the paraxial region, it may indicate that the peripheral region may be other shape, such as convex or flat.
(1-3. The second lens element 22)
The second lens element 22 (also referred to as the lens element 22) has positive refractive power. The second lens element 22 has an object-side surface 22a and an image-side surface 22b. The image-side surface 22b may be convex at least in a paraxial region, so that the positive refractive power of the first lens element 21 can be balanced for avoiding the excessive distribution of refractive power from the first lens element 21. Therefore, the spherical aberration of the optical system 2 can be corrected. The object-side surface 22a may also be convex. The object-side surface 22a and/or the image-side surface 22b may be aspheric.
(1-4. The third lens element 23)
The third lens element 23 (also referred to as the lens element 23) has negative refractive power. The third lens element 23 has an object-side surface 23a and an image-side surface 23b. The image-side surface 23b may be concave at least in a paraxial region, so that the aberration generated from the first lens element 21 and the second lens element 22 can be reduced. The object-side surface 23a may be convex at least in a paraxial region. The object-side surface 23a and/or the image-side surface 23b may be aspheric.
(1-5. The fourth lens element 24)
The fourth lens element 24 (also referred to as the lens element 24) may have positive refractive power. The fourth lens element 24 has an object-side surface 24a and an image-side surface 24b. The object-side surface 24a may be convex at least in a paraxial region and the image-side surface 24b may be concave at least in a paraxial region, so that the astigmatism of the optical system 2 can be corrected. The object-side surface 24a and/or the image-side surface 24b may be aspheric.
As an example of the present embodiment, the object-side surface 24a may change from convex at a paraxial region thereof to concave at a peripheral region thereof, and the image-side surface 24b may change from concave at a paraxial region thereof to convex at a peripheral region thereof. Therefore, the incident angle from the off-axis field of the optical  system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected.
(1-6. The fifth lens element 25)
The fifth lens element 25 (also referred to as the lens element 25) has positive refractive power. The fifth lens element 25 has an object-side surface 25a and an image-side surface 25b. The object-side surface 25a may be concave and the image-side surface 25b is convex. Therefore, the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality. The object-side surface 25a and/or the image-side surface 25b may be aspheric.
(1-7. The sixth lens element 26)
The sixth lens element 26 (also referred to as the lens element 26) has negative refractive power. The sixth lens element 26 has an object-side surface 26a and an image-side surface 26b. The image-side surface 26b is concave at least in a paraxial region. Therefore, the principal point of the optical system 2 can be positioned away from the image plane. The optical path length, the back focal length, and the size of the optical system 2 can be reduced. The image-side surface 26b is at least partially aspheric. The image-side surface 26b changes from concave at a paraxial region thereof to convex at a peripheral region thereof. Therefore, the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected. The object-side surface 26a may also be concave. The object-side surface 26a may be at least partially aspheric.
(1-8. The IR cut filter 29)
The IR cut filter 29 may be made of infrared absorption ink over a substrate. The substrate may be made of plastic material or glass material. As an example, a glass substrate with a thickness of 0.11 mm made of borosilicate glass can be used as the substrate. The IR cut filter 29 does not affect the focal length of the optical system 2.
(1-9. Optical characteristic of the optical system 2)
In the optical system 2, the following conditional Expression 1 is satisfied. Here, f1 is a focal length of the first lens element 21, and f2 is a focal length of the second lens element 22.
[Expression 1]
0<f2/f1<15.0
Therefore, the spherical aberration generated from the optical system 2 can be reduced by properly arranging the positive refractive power of the first lens element 21 and the second lens element 22. The lower limit value of Expression 1 may be 0.2, 0.25, 0.4, 0.5 or 1.0. The upper limit value of Expression 1 may be 10.0, 5.0, 4.8, 2.0 or 1.0. For example, Expression 1 may be 0<f2/f1<10.0, 0<f2/f1<2.0, 0<f2/f1<5.0, 0.2<f2/f1<5.0, 0.5<f2/f1<5.0 or 1.0<f2/f1<10.
The following conditional Expression 2 may also be satisfied. Here, f is a focal length of the optical system 2. As an example in the present embodiment, fmay be between 2.16 mm and 3.28 mm. Furthermore, f4 is a focal length of the fourth lens element 24.
[Expression 2]
0< (f/f1) / ( (f/f2) + (f/f4) ) <5.0
Therefore, the telephoto functionality of the optical system 2 can be enhanced to reduce the back focal length and the total track length of the optical system 2, so that the optical system 2 can be applied to compact and portable electronics. For example, Expression 2 may be satisfied when the refractive power of the second lens element 22 and the fourth lens element 24 is small, the refractive power of the first lens element 21 is large. The refractive power of the second lens element 22 may be larger than the refractive power of the fourth lens element 24. Focal lengths of the third lens element 23 and the fifth lens element 25 may be designed to have larger aspherical coefficiencies so that an F-number and back focus of the optical system 2 are maintained. The lower limit value of Expression 2 may be 0.2 or 0.35. The upper limit value of Expression 2 may be 3.0, 2.0, 1.0 or 0.75. For example, Expression 2 may be 0< (f/f1) / ( (f/f2) + (f/f4) ) <3.0, 0< (f/f1) / ( (f/f2) + (f/f4) ) <2.0 or 0< (f/f1) / ( (f/f2) + (f/f4) ) <1.0.
The following conditional Expression 3 may also be satisfied. Here, f3 is a focal length of the third lens element 23, f5 is a focal length of the fifth lens element 25, and f6 is a focal length of the sixth lens element 26.
[Expression 3]
0< (f/f1) + (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) + (f/f6) <1.0
In Expression 3, the portion surrounded by the inequality signs may express a Petzval sum of the optical system 2, and may relate to astigmatism of the optical system 2. Since the Petzval sum is less than 1.0, the astigmatism of the optical system 2 is small and the MTF (Modulated Transfer Function) is favorable.
Instead of or in addition to Expression 3, any combination of the following conditional Expression 3’, the following conditional Expression 3”and the following conditional Expression 3”’may also be satisfied.
[Expression 3’]
0.15< (f/f1) + (f/f3) + (f/f5) / ( (f/f2) + (f/f4) + (f/f5) + (f/f6) <0.25
[Expression 3”]
0< (f/f1) (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) <8.0
[Expression 3”’]
0< (f/f1) / ( (f/f2) (f5) + (f/f4) ) <2.0
If Expression 3”and/or Expression 3”’are satisfied, the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected. The upper limit value of Expression 3”may be 2.0.
The following conditional Expression 4 may also be satisfied.
[Expression 4]
-0.5<f/f4<1.5
Therefore, the sensitivity indicating the degree to which the optical system 2 is affected by the allowance tilt when the optical system 2 is assembled within the housing can be reduced by properly adjusting the refractive power of the fourth lens element 24. The lower limit value of Expression 4 may be -0.25 or -0.2. The upper limit value of Expression 4 may be 0.75, 0.5, or 0.45. For example, Expression 4 may be -0.5<f/f4<0.75 or -0.25<f/f4<1.5. As an example, f/f4 may be 0.05.
The following conditional Expression 5 may also be satisfied. Here, V1 is an Abbe number of the first lens element 21, and V3 is an Abbe number of the third lens element 23.
[Expression 5]
0.1<V3/V1<1.0
Therefore, the chromatic aberration of the optical system 2 can be corrected. The lower limit value of Expression 5 may be 0.2, 0.25 or 0.3. The upper limit value of expression 5 may be 0.5 or 0.35. For example, expression 5 may be 0.2<V3/V1<0.35 or 0.3<V3/V1<0.5. As an example, V1 may be 53.0, V3 may be 20.4, and V3/V1 may be 0.384.
The following conditional Expression 6 may also be satisfied. Here, R7 is a curvature radius of the object-side surface 24a of the fourth lens element 24.
[Expression 6]
0.2<f/R7<20.0
Therefore, the sensitivity of the optical system 2 can be reduced effectively by properly adjusting the curvature of the object-side surface 24a of the fourth lens element 24. The lower limit value of Expression 6 may be 0.5, 0.6, 0.8, 1.0, or 1.5. The upper limit value of Expression 6 may be 10.0, 3.2, 3.0, 2.4, 2.2, or 1.65. For example, Expression 6 may be 0.2<f/R7<20.0, 0.2<f/R7<10.0, 0.5<f/R7<20.0, 1<f/R7<3.2, 1<f/R7<3.0, or 1.5<f/R7<1.65.
The following conditional Expression 7 may also be satisfied. Here, R3 is a curvature radius of the object-side surface 22a of the second lens element 22, and R4 is a curvature radius of the image-side surface 22b of the second lens element 22.
[Expression 7]
-0.5< (R3+R4) / (R3-R4) <0.75
Therefore, the aberration (e.g. spherical aberration) of the optical system 2 can be corrected by properly adjusting the curvature of the optical surfaces of the second lens element 22. The lower limit value of Expression 7 may be -0.4, -0.2, or 0.25. The upper limit value of Expression 7 may be 0.55, 0.5, or 0.4. For example, Expression 7 may be -0.5< (R3+R4) / (R3-R4) <0.55, -0.5< (R3+R4) / (R3-R4) <0.5, -0.4< (R3+R4) / (R3-R4) <0.55, or 0.25< (R3+R4) / (R3-R4) <0.75.
The following conditional Expression 8 and/or the following Expression 8’may also be satisfied. Here, T23 is an axial distance between the second lens element 22 and the third lens element 23. ET23 is a distance in parallel with an optical axis between a maximum effective diameter position on the image-side surface 22b of the second lens element 22 and a maximum effective diameter position on the object-side surface 23a of the third lens element 23. T34 is an axial distance between the third lens element 23 and the fourth lens element 24. ET34 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface 23b of the third lens element 23 and a maximum effective diameter position on an object-side surface 24a of the fourth lens element 24.
[Expression 8]
0<T23/ET23<0.55
[Expression 8’]
0<T34/E34<0.01
Therefore, the yield rate of assembling the optical system 2 can be increased by properly arranging thickness of the lens elements 22, 23 and the distance between them and/or thickness of the  lens elements  23, 24 and the distance between them, in order to avoid interference of the lens elements. Moreover, distortion of the optical system 2 can be balanced between the lens elements 21 to 26 and can be reduced in total. The upper limit value of Expression 8 may be 0.45, 0.30, or 0.20. For example, Expression 8 may be 0<T23/ET23<0.45 or 0<T23/ET23<0.20.
The following conditional Expression 9 may also be satisfied. Here, T12 is an axial distance between the first lens element 21 and the second lens element 22. T45 is an axial distance between the fourth lens element 24 and the fifth lens element 25.
[Expression 9]
0.05< (T12+T23) / (T34+T45) <0.75
By properly arranging the distances between the lens elements 21 to 26, assembling of the optical system 2 can be made easier and the yield rate of the optical system 2 can be improved. The lower limit value of Expression 9 may be 0.15 or 0.25. The upper limit value of Expression 9 may be 0.35. For example, Expression 9 may be 0.15< (T12+T23) / (T34+T45) <0.35.
Any combination of the following conditional Expression 10, the following conditional Expression 11 and the following conditional Expression 12 may also be satisfied. Here, CT2 is a central thickness of the second lens element 22. CT3 is a central thickness of the third lens element 23. CT4 is a central thickness of the fourth lens element 24. CT5 is a central thickness of the fifth lens element 25.
[Expression 10]
0.15<CT3/CT2<0.80
[Expression 11]
0.20 mm<CT3+CT4<0.65 mm
[Expression 12]
0.50 mm<CT3+CT4+CT5<1.25 mm
A lens element with a thickness that is too large or too small would be poorly fabricated and/or easily broken. Therefore, the yield rate of the lens elements 22 to 25 can be increased by properly setting the thicknesses of these lens elements. The image-side lens elements, such as the lens elements 21 and 22, can be thick than the object-side lens elements, such as the lens elements 23 to 26, when two or three of Expressions 10-12 are satisfied. The lower limit value of Expression 10 may be 0.2. The upper limit value of Expression 11 may be 0.5.
The following conditional Expression 13 may also be satisfied. Here, Fno is an f-number of the optical system 2, which may be a ratio of focal length to an aperture of the optical system 2. As an example in the present embodiment, Fno may be between 2.0 and 2.2.
[Expression 13]
0.5<Fno<3.0
Therefore, the optical system 2 can have a large aperture, so that the optical system 2 can capture clear images by a high-speed shutter in a low light environment along with a  longer depth of field. The lower limit value of Expression 13 may be 1.5 or 1.6. The upper limit value of Expression 13 may be 2.8, 2.5, 2.2, or 2.0. For example, expression 13 may be 1.25<Fno<2.5, 1.5<Fno<2.5, or 1.5<Fno<2.8.
Concerning other characteristics, the TTL (through the lens) of the optical system 2 may be 4.5 mm, and the FOV (field of view) of the optical system 2 may be between 75 and 78 degrees. As an example, the HFOV (half of the maximal field of view) may be 37.5 degrees.
(2. The image sensor 3)
The image sensor 3 may be a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) sensor. The image sensor 3 may be a 1/3.2 type, and the effective size may be 4.5 mm × 3.4 mm. The single pixel size of the image sensor 3 may be a small size such as 1.12 um, 1.0 um, or 0.9 um. The image sensor 3 may be disposed on the image plane of the optical system 2. The image sensor 3 may be operable to be moved by an anti-shaking correction mechanism. As an example, the image sensor 3 may be operable to move in the direction of the optical axis of the optical system 2, or may be operable to move in one or two directions orthogonal to the optical axis.
In an embodiment described above, the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced. The second lens element 22 haspositive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected. The third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced. The fourth lens element 24 has a convex object-side surface 24a at least in a paraxial region and a concave image-side 24b surface at least in a paraxial region, and therefore the astigmatism of the optical system 2 can be corrected. The fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected to enhance the resolving power and the image quality. The image-side surface 26b of the sixth lens element 26 changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected. The conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced. The conditional Expression 2 is satisfied, and therefore the telephoto functionality of the optical system 2 can be enhanced to reduce the back focal length and the total track length of the optical system 2, so that the optical system 2 can be applied to compact and portable electronics. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
In another embodiment, the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced. The second lens element 22 has positive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected. The third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced. The fourth lens element 24 has a convex object-side surface 24a at least in a paraxial region and a  concave image-side 24b surface at least in a paraxial region, and therefore the astigmatism of the optical system 2 can be corrected. The fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality. The image-side surface 26b of the sixth lens element 26 changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected. The conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced. The conditional Expression 3”is satisfied, and therefore the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected. The conditional expression 5 is satisfied, and therefore the sensitivity of the optical system 2 can be reduced effectively by properly adjusting the curvature of the object-side surface 24a of the fourth lens element 24. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
In another embodiment, the first lens element 21 has positive refractive power and has the convex object-side surface 21a at least in a paraxial region, and therefore the total track length of the system can be reduced. The second lens element 22 has positive refractive power, and therefore the spherical aberration of the optical system 2 can be corrected. The third lens element 23 has negative refractive power, and therefore the aberration generated from the first and second lens elements 21 and 22 can be reduced. The fifth lens element 25 has positive refractive power and has a convex image-side surface 25b at least in a paraxial region, and therefore the high order aberration of the optical system 2 can be corrected for enhancing the resolving power and the image quality. The six lens element 26 has a concave image-side surface 26b at least in a paraxial region, and the image-side surface 26b changes from concave at a paraxial region to convex at a peripheral region, and therefore the incident angle from the off-axis field of the optical system 2 to the image sensor 3 can be effectively reduced, and the aberration of the off-axis field can be further corrected. The conditional Expression 1 is satisfied, and therefore the spherical aberration generated from the optical system 2 can be reduced. The conditional Expression 3”’is satisfied, and therefore the focal point of each lens element 21 to 26 is suitably arranged and the field curvature is corrected. The conditional expression 13 is satisfied, and therefore the optical system 2 can capture clear images by a high-speed shutter at the low light environment along with a longer depth of field. Based on the above, it is possible to realize higher performance capabilities while preventing an increase in the size of the optical system 2.
(3. Material of the lens elements 21 to 26)
According to the optical system 2 of the present disclosure, the lens elements 21 to 26 can be made of glass material or plastic material independently. When at least one of the lens elements 21 to 26 is made of glass material, the distribution of the refractive power of the optical system 2 may be more flexible to design. Furthermore, the TTL (through the lens) and aberration including chromatic aberration of the optical system 2 can be reduced. When at least one of the lens elements 21 to 26 is made of plastic material, the manufacturing costs  can be effectively reduced. Furthermore, the optical surfaces can be made aspheric easily. As a result, more controllable variables are obtained, and the aberration of the optical system 2 can be reduced while maintainingthe number of lens elements. Therefore, by using both of glass material and plastic material, the total track length of the optical system 2 can also be reduced. For example, two of the lens elements 21 to 26 may be made of glass material and the remaining four lens elements may be formed of plastic material. As an example in the present embodiment, the first lens element 21 and the fifth lens element 25 may be made of glass material. The second lens element 22, the third lens element 23, the fourth lens element 24 and the sixth lens element 26 may be made of plastic material. In another example, the first lens element 21 and the fourth lens element 24 may be made of glass material. The second lens element 22, the third lens element 23, the fifth lens element 25 and the sixth lens element 26 may be made of plastic material.
The lens material may be selected from materials having dimensional stability, molding easiness, high refractive index and/or high Abbe number. As an example, commercially available low dispersion glass can be used as the glass material. The plastic material may be a material for which Nd (the refractive index with respect to the d line) is 1.66 and vd (Abbe number) is 20.4, or a material for which Nd is 1.55 and vd is 53.0. Commercially available cyclo-olefin polymer resin or commercially available polycarbonate resin can be used as the plastic material.
(4. Embodiment examples)
Table 1 shows an embodiment example of the camera module 1 according to the present embodiment.
[Table 1]
Figure PCTCN2017117535-appb-000001
In the table 1, the first column (surface number) indicates the object-side and image-side optical surfaces 21a to 26b of the optical elements 21 to 26. The optical surfaces “29a” and “29b” are the object-side and image-side optical surfaces of the IR cut filter 29.
The second column (surface type) indicates the shape of the optical surface. Here, “Standard” indicates a planar surface, and “Even Aspheric” indicates a flat aspherical surface.
The third column (Comment) shows remarks, wherein “f=4.1” indicates that the focal distance of the optical system 2 is 4.1 and “M-FCD1” , “K26R” , and “EP8000” indicate that the optical elements are formed of the corresponding materials described above.
Furthermore, “16M (1/3.2) ” indicates that the image sensor 3 is a 1/3.2 type with 16 megapixels.
The fourth column (Radius) indicates the curvature radius. The fifth column (Thickness) indicates the distance between surfaces. The sixth column (nd, vd) indicates the refractive index with respect to the d line and the Abbe number. The seventh column (Semi-diameter) indicates the radius, and the eighth column (Conic) indicates the conic coefficient.
Table 2 shows another embodiment example of the camera module 1 according to the present embodiment. The camera module 1 may satisfy the values shown in Table 2.
[Table 2]
Figure PCTCN2017117535-appb-000002
(4-1. Optical surfaces of the lens elements 21 to 26)
The aspheric surface profiles (sag quantities) of the lens elements 21 to 26 are expressed by the following Expression 20.
[Expression 20]
Figure PCTCN2017117535-appb-000003
Here, C is the curvature of the surface, k is the conic constant, r is the distance from the point on the optical surface to the optical axis in radial direction, and A i is the aspheric coefficient. Furthermore, i may be either an even number or an odd number, and N may be approximately 240.
Table 3 shows the aspheric coefficient A i of each optical surface.
[Table 3]
Figure PCTCN2017117535-appb-000004
In the table 3, the first column (surface number) indicates the object-side and image-side optical surfaces 21a to 26b of the optical elements 21 to 26 and the object-side and image-side optical surfaces 29a and 29b of the IR cut filter 29. The second and following columns indicate the aspherical surface coefficient of each order.
FIG. 3 shows the field curvature of the camera module 1. In this figure, the vertical axis indicates the height from the optical axis, and the horizontal axis indicates the magnitude of the field curvature. Graph S shows the field curvature at the sagittal surface, and Graph T shows the field curvature at the tangential surface (meridional surface) .
FIG. 4 shows the distortion of the camera module 1. In this figure, the vertical axis indicates the ideal image height, and the horizontal axis indicates the magnitude of the distortion, i.e. the amount of skew of the actual height of the image relative to the ideal height of the image.
FIG. 5 shows spot diagrams of the camera module 1. As an example, the upper left diagram shows the spot diagram in a case where the position of the image sensor is the best focused position and the light rays from the object form an angle of 0° with the optical axis. Furthermore, the upper right diagram shows the spot diagram in a case where the position of the image sensor is shifted by 1.097 mm on the optical axis and the light rays from the object form an angle of 20° with the optical axis. The points plotted in this figure respectively indicate focal positions of light rays with wavelengths of 0.5461, 0.5876, 0.4861, 0.4358, and 0.6563 (nm) .
FIG. 6 shows the OTF curve of the camera module 1. In this figure, the horizontal axis indicates the spatial frequency and the vertical axis indicates the resolution ratio. Each graph shows the OTF curve of sagittal light rays and tangential light rays forming angles of 0, 10, 20, 30, 35, 40, and 45 (degrees) relative to the optical axis at the image plane.
In the embodiment described above, the image sensor 3 is described as being moved by the anti-shaking correction mechanism. Instead of this, at least one of the lens elements 21 to 26 in the optical system 2 may be moved. Furthermore, the image sensor 3 and at least one of the lens elements 21 to 26 in the optical system 2 may be moved by a zoom mechanism and/or focus mechanism, which are not shown in the figures.
Furthermore, the camera module 1 is described as including the image sensor 3. However, if the image sensor 3 is detachable to the camera module 1, the image sensor 3 does not need to be equipped in the camera module 1.
Furthermore, the electronic apparatus 100 is described as a movile device. Instead of this, the electronic apparatus 100 may be an on-vehicle camera, a robot eye, a security apparatus or an unmanned aircraft, such as a drone.
While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention.
The operations, procedures, steps, and stages of each process performed by an apparatus, system, program, and method shown in the claims, embodiments, or diagrams can be performed in any order as long as the order is not indicated by “prior to, ” “before, ” or the like and as long as the output from a previous process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order.
As made clear from the above, the embodiments of the present invention can be used to realize an optical system and a device that realizes higher performance capabilities while preventing an increase in size.

Claims (40)

  1. An optical system comprising, in order from an object side to an image side:
    a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region;
    a second lens element with positive refractive power;
    a third lens element with negative refractive power;
    a fourth lens element having a convex object-side surface at least in a paraxial region and a concave image-side surface at least in a paraxial region,
    a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and
    a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof;
    Wherein the following conditional expressions are satisfied:
    0<f2/f1<15.0; and
    0< (f/f1) / ( (f/f2) + (f/f4) ) <5.0,
    Where f is a focal length of the optical system, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, and f4 is a focal length of the fourth lens element.
  2. The optical system of claim 1, wherein the following conditional expressions are satisfied:
    0<f2/f1<5.0; and
    0< (f/f1) / ( (f/f2) + (f/f4) ) <3.0.
  3. The optical system of claim 1 or 2, wherein the following conditional expression is satisfied:
    0< (f/f1) + (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) + (f/f6) <1.0
    where f3 is a focal length of the third lens element, f5 is a focal length of the fifth lens element, and f6 is a focal length of the sixth lens element.
  4. The optical system of any one of claims 1-3, wherein the following conditional expression is satisfied:
    0.15< (f/f1) + (f/f3) + (f/f5) / ( (f/f2) + (f/f4) + (f/f5) + (f/f6) <0.25.
  5. The optical system of any one of claims 1-4, wherein the following conditional expression is satisfied:
    0< (f/f1) (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) <8.0.
  6. The optical system of any one of claims 1-5, wherein the following conditional expression is satisfied:
    0< (f/f1) / ( (f/f2) (f5) + (f/f4) ) <2.0.
  7. The optical system of any one of claims 1-6, wherein the following conditional expression is satisfied:
    -0.5<f/f4<1.5.
  8. The optical system of any one of claims 1-7, wherein the following conditional expression is satisfied:
    0.1<V3/V1<1.0
    where V1 is an Abbe number of the first lens element, and V3 is an Abbe number of the third lens element.
  9. The optical system of any one of claims 1-8, wherein the following conditional expression is satisfied:
    0.2<f/R7<20.0
    where R7 is a curvature radius of the object-side surface of the fourth lens element.
  10. The optical system of any one of claims 1-9, wherein the following conditional expression is satisfied:
    0<T23/ET23<0.55
    where T23 is an axial distance between the second lens element and the third lens element, and ET23 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface of the second lens element and a maximum effective diameter position on an object-side surface of the third lens element.
  11. The optical system of any one of claims 1-10, wherein the following conditional expression is satisfied:
    0<T34/E34<0.01
    Where T34 is an axial distance between the third lens element and the fourth lens element, and ET34 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface of the third lens element and a maximum effective diameter position on an object-side surface of the fourth lens element.
  12. The optical system of any one of claims 1-11, wherein the following conditional expression is satisfied:
    -0.5< (R3+R4) / (R3-R4) <0.75
    where R3 is a curvature radius of an object-side surface of the second lens element, and R4 is a curvature radius of an image-side surface of the second lens element.
  13. The optical system of claim 12, wherein the following conditional expression is satisfied:
    -0.4< (R3+R4) / (R3-R4) <0.55.
  14. The optical system of any one of claims 1-13, wherein the following conditional expression is satisfied:
    0.05< (T12+T23) / (T34+T45) <0.75
    where T12 is an axial distance between the first lens element and the second lens element, T23 is an axial distance between the second lens element and the third lens element, T34 is an axial distance between the third lens element and the fourth lens element, and T45 is an axial distance between the fourth lens element and the fifth lens element.
  15. The optical system of any one of claims 1-14, wherein the following conditional expression is satisfied:
    0.15<CT3/CT2<0.80
    where CT2 is a central thickness of the second lens element, and CT3 is a central thickness of the third lens element.
  16. The optical system of any one of claims 1-15, wherein the following conditional expression is satisfied:
    0.50 mm<CT3+CT4+CT5<1.25 mm
    where CT3 is a central thickness of the third lens element, CT4 is a central thickness of the fourth lens element, and CT5 is a central thickness of the fifth lens element.
  17. The optical system of any one of claims 1-16, wherein the following conditional expression is satisfied:
    0<f2/f1<2.0.
  18. The optical system of claim 17, wherein the first lens element has a concave image-side surface at least in a paraxial region, the second lens element has a convex image-side surface at least in a paraxial region, and the third lens element has a concave image-side surface at least in a paraxial region.
  19. The optical system of claim 17 or 18, wherein the following conditional expression is satisfied:
    0.20 mm<CT3+CT4<0.65 mm
    where CT3 is a central thickness of the third lens element, and CT4 is a central thickness of the fourth lens element.
  20. The optical system of any one of claims 17-19, wherein the following conditional expression is satisfied:
    0.5<Fno<3.0
    where Fno is an f-number of the optical system.
  21. The optical system of any one of claims 1-20, wherein the object-side surface of the fourth lens element changes from convex at a paraxial region thereof to concave at a peripheral region thereof, and the image-side surface of the fourth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof.
  22. The optical system of any one of claims 1 to 21, wherein the following conditional expression is satisfied:
    0.15<CT3/CT2<0.80
    where CT2 is a central thickness of the second lens element, and CT3 is a central thickness of the third lens element.
  23. An optical system comprising, in order from an object side to an image side:
    a first lens element with positive refractive power having a convex object-side surface at least in a paraxial region;
    a second lens element with positive refractive power;
    a third lens element with negative refractive power;
    a fourth lens element having a convex object-side surface at least in a paraxial region;
    a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and
    a sixth lens element with negative refractive power, wherein an image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a paraxial regionl region thereof;
    wherein the following conditional expressions are satisfied:
    0<f2/f1<15;
    0< (f/f1) (f/f3) / ( (f/f2) + (f/f4) ) + (f/f5) <8.0; and
    0.5<f/R7<20.0
    where f is a focal length of the optical system is f, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, f3 is a focal length of the third lens element, f4 is a focal length of the fourth lens element, f5 is a focal length of the fifth lens element, and R7 is a curvature radius of the object-side surface of the fourth lens element.
  24. The optical system of claim 23, wherein the following conditional expression is satisfied:
    1<f/R7<3.2.
  25. The optical system of claim 23 or 24, wherein the following conditional expression is satisfied:
    -0.5<f/f4<1.5.
  26. The optical system of any one of claims 23-25, wherein the object-side surface of the fifth lens element is concave at least in a paraxial region.
  27. The optical system of any one of claims 23-26, wherein the first lens element has a concave image-side surface at least in a paraxial region, the second lens element has a convex image-side surface at least in a paraxial region, and the following conditional expression is satisfied:
    1.0<f2/f1<10.
  28. The optical system of any one of claims 23-27, wherein the following conditional expression is satisfied:
    0<T23/ET23<0.55
    Where T23 is an axial distance between the second lens element and the third lens element, and ET23 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface of the second lens element and a maximum effective diameter position on an object-side surface of the third lens element.
  29. The optical system of any one of claims 23-28, wherein the following conditional expression is satisfied:
    -0.5< (R3+R4) / (R3-R4) <0.75
    Where R3 is a curvature radius of an object-side surface of the second lens element, and R4 is a curvature radius of an image-side surface of the second lens element.
  30. The optical system of any one of claims 23-29, wherein the following conditional expression is satisfied:
    0.50 mm<CT3+CT4+CT5<1.25 mm
    Where CT3 is a central thickness of the third lens element, CT4 is a central thickness of the fourth lens element, and CT5 is a central thickness of the fifth lens element.
  31. The optical system of any one of claims 28-30, wherein the following conditional expression is satisfied:
    0.1<V3/V1<1.0
    Where V1 is an Abbe number of the first lens element, and V3 is an Abbe number of the third lens element.
  32. An optical system comprising, in order from an object side to an image side:
    a first lens element with positive refractive power having a convex object side surface at least in a paraxial region;
    a second lens element with positive refractive power;
    athird lens element with negative refractive power;
    a fourth lens element;
    a fifth lens element with positive refractive power having a convex image-side surface at least in a paraxial region; and
    a sixth lens element with negative refractive power having a concave image-side surface at least in a paraxial region, wherein the image-side surface of the sixth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof;
    wherein the following conditional expressions are satisfied:
    0<f2/f1<15.0;
    0< (f/f1) / ( (f/f2) (f5) + (f/f4) ) <2.0; and
    0.5<Fno<3.0
    where f is a focal length of the optical system, f1 is a focal length of the first lens element, f2 is a focal length of the second lens element, f4 is a focal length of the fourth lens element, f5 is a focal length of the fifth lens element, and Fno is an f-number of the optical system.
  33. The optical system of claim 23, wherein the following conditional expressions are satisfied:
    0<f2/f1<10.0;
    0< (f/f1) / ( (f/f2) (f5) + (f/f4) ) <2.0; and
    0.5<Fno<3.0.
  34. The optical system of claim 32 or 33, wherein the following conditional expression is satisfied:
    0.1<V3/V1<1.0
    where V1 is an Abbe number of the first lens element, and V3 is an Abbe number of the third lens element.
  35. The optical system of any one of claims 32-34, wherein the second lens element has a convex image-side surface at least in a paraxial region, and the following conditional expression is satisfied:
    0< (f/f1) / ( (f/f2) + (f/f4) ) <5.0.
  36. The optical system of any one of claims 32-35, wherein the following conditional expressions are satisfied:
    0<T23/ET23<0.55;
    0<T34/E34<0.01
    where T23 is an axial distance between the second lens element and the third lens element, ET23 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface of the second lens element and a maximum effective diameter position on an object-side surface of the third lens element, T34 is an axial distance between the third lens element and the fourth lens element, and ET34 is a distance in parallel with an optical axis between a maximum effective diameter position on an image-side surface of the third lens element and a maximum effective diameter position on an object-side surface of the fourth lens element.
  37. The optical system of any one of claims 32-36, wherein the following conditional expression is satisfied:
    0.05< (T12+T23) / (T34+T45) <0.75
    where T12 is an axial distance between the first lens element and the second lens element, T23 is an axial distance between the second lens element and the third lens element, T34 is an axial distance between the third lens element and the fourth lens element, and T45 is an axial distance between the fourth lens element and the fifth lens element.
  38. The optical system of any one of claims 32-37, wherein the object-side surface of the fourth lens element changes from convex at a paraxial region thereof to concave at a peripheral region thereof, and the image-side surface of the fourth lens element changes from concave at a paraxial region thereof to convex at a peripheral region thereof.
  39. A camera module comprising:
    the optical system of any one of claims 1-38; and
    an image sensor.
  40. An electronic apparatus comprising:
    the camera module of claim 39;
    a display section; and
    a control section that controls the camera module and the display section.
PCT/CN2017/117535 2017-12-20 2017-12-20 Optical system, camera module and electronic apparatus WO2019119312A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103576295A (en) * 2012-08-08 2014-02-12 大立光电股份有限公司 Optical photographing lens system
JP2014044250A (en) * 2012-08-24 2014-03-13 Sony Corp Image pickup lens and image pickup device
CN105044880A (en) * 2015-03-11 2015-11-11 瑞声声学科技(深圳)有限公司 Camera lens system
CN105717609A (en) * 2014-12-05 2016-06-29 大立光电股份有限公司 Optical image capture battery of lens, image capture apparatus and electronic apparatus
KR101690479B1 (en) * 2016-03-07 2016-12-28 주식회사 세코닉스 High-resolution photographing lens system
CN206710685U (en) * 2017-02-17 2017-12-05 浙江舜宇光学有限公司 Pick-up lens

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103576295A (en) * 2012-08-08 2014-02-12 大立光电股份有限公司 Optical photographing lens system
JP2014044250A (en) * 2012-08-24 2014-03-13 Sony Corp Image pickup lens and image pickup device
CN105717609A (en) * 2014-12-05 2016-06-29 大立光电股份有限公司 Optical image capture battery of lens, image capture apparatus and electronic apparatus
CN105044880A (en) * 2015-03-11 2015-11-11 瑞声声学科技(深圳)有限公司 Camera lens system
KR101690479B1 (en) * 2016-03-07 2016-12-28 주식회사 세코닉스 High-resolution photographing lens system
CN206710685U (en) * 2017-02-17 2017-12-05 浙江舜宇光学有限公司 Pick-up lens

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