JP6430206B2 - The camera module - Google Patents

Description

The present invention is related to a camera module for imaging a subject through the lens.

  An electronic device such as a digital camera or a mobile phone has a built-in camera module for photographing a subject and converting it into an image signal. The camera module includes an image sensor that images a subject and a lens unit that forms an image of the subject on the image sensor. The lens unit is usually composed of a plurality of lenses.

  In the camera module, it is necessary to remove unnecessary incident light and reflected light to prevent the occurrence of flare, ghost, and the like and to improve the image quality of the captured image. For this reason, a lens unit having a light shielding plate for cutting unnecessary light, a lens having a light shielding material with low glossiness for reducing reflected light while cutting unnecessary light, and the like have been proposed.

  Patent Document 1 discloses a lens unit having a light shielding plate that is inserted between lenses and is disposed at a position where unnecessary light generated by reflection of each lens surface or the like is not incident on another lens. .

  Patent Document 2 discloses a method for manufacturing an optical lens with a light shielding material having a concavo-convex shape on the lens surface in order to reduce reflected light on the surface of the light shielding material.

JP 2009-048024 A JP 2012-208391 A

  In recent years, camera modules are required to have both a large aperture for increasing brightness and a reduction in thickness for miniaturization, and this requirement is expected to become stricter in the future. For this reason, the incident angle of light incident on the light shielding plate mounted on the camera module is further increased, but even in this case, a configuration that can further suppress the reflection of light on the surface of the light shielding plate is required. Here, the incident angle refers to an angle formed between the normal to the light shielding plate surface and the light incident direction.

  However, when the lens unit disclosed in Patent Document 1 is applied to a thin camera module in recent years, flare and ghost may occur due to reflected light on the surface of the light shielding plate.

  In addition, the lens disclosed in Patent Document 2 has a concavo-convex shape on the surface of the light shielding material. However, the disclosed concavo-convex shape cannot sufficiently reduce the reflection of light having a large incident angle. And ghosting may occur.

The present invention has been made in view of the above circumstances, to reduce the reflection of a large light incident angle, to provide a camera module for suppressing thin flare and ghost due to the reflection of the light shielding plate surface For the purpose.

In order to solve the above problems, a camera module of the present invention includes a lens unit in which a plurality of lenses and at least one light-shielding plate are stacked in the optical axis direction of the lens, an imaging element that images a subject through the lens unit, have. At least a part of the light shielding plate is provided with an antireflection portion whose refractive index increases from the surface of the light shielding plate toward the inside of the light shielding plate, and from the surface closest to the subject to the imaging element among the surfaces of the plurality of lenses TTL / f ≦ 1.3, where TTL is TTL and the combined focal length of the lens unit is f. The antireflection portion includes a rough concavo-convex structure having an average period longer than the longest wavelength λB in the wavelength band of light to be shielded, and the rough concavo-convex structure, which is the most in the wavelength band of light to be shielded. A moth-eye structure that is a fine concavo-convex structure having an average period smaller than ½ of the short wavelength λA, the light shielding plate has a base material made of Al, and the base material has the rough concavo-convex structure. The fine concavo-convex structure is made of Ni plating.

The average height of the fine concavo-convex structure is preferably 1/2 or more of λB.

  The average height of the rough concavo-convex structure is preferably ½ or more of λB.

  It is preferable that the light shielding member has an antireflection structure by unevenness formed on the surface.

  It is preferable that the light shielding plate is included in the lens.

  According to the present invention, since the reflection of light having a large incident angle is reduced, the occurrence of flare and ghost can be suppressed even when incorporated into a thin electronic device.

It is a surface side perspective view of the electronic device of the present invention. It is a back side perspective view of the electronic device of the present invention. It is sectional drawing of the electronic device of FIG. It is sectional drawing of the camera module of this invention. It is a disassembled perspective view of the lens unit of this invention. It is explanatory drawing of the light-shielding plate of 1st Embodiment. It is the elements on larger scale of a lens unit. It is explanatory drawing of the light-shielding plate of 2nd Embodiment. It is explanatory drawing of the light-shielding plate of 3rd Embodiment. It is explanatory drawing of the lens of 4th Embodiment. It is explanatory drawing of the manufacturing method of the lens of 4th Embodiment. It is explanatory drawing of the conventional antireflection part. It is explanatory drawing of the conventional antireflection part.

“First Embodiment”
As an example of the electronic apparatus of the present invention, a smartphone 10 is shown in FIGS. As illustrated in FIG. 1, the smartphone 10 includes a touch panel display input unit 11 on one side, and a predetermined instruction is given to the smartphone 10 by operating the display input unit 11 with a finger or the like. As shown in FIG. 2, a camera module 20 is provided on the other surface of the smartphone 10, and still images and moving images can be taken using the camera module 20. Still images and moving images captured by the camera module 20 can be displayed on the display input unit 11.

  FIG. 3 is a cross-sectional view of the smartphone 10, and the optical axis Ax of the camera module 20 showing the camera module 20 mounted on the smartphone 10 matches the thickness direction of the smartphone 10.

  FIG. 4 is a cross-sectional view of the camera module 20. In the camera module 20, a lens unit 21, a focus driving unit 22, and an image sensor 23 are provided inside a housing 24.

  Here, the operation of the camera module 20 will be described. When a subject is photographed by the smartphone 10, the focus control unit 22 drives the lens unit 21 in the direction of the optical axis Ax by an AF control unit (not shown) provided in the camera module. The focus is adjusted by adjusting the distance from the camera 23.

  The subject light entering from the opening 28 of the lens unit 21 is condensed on the image sensor 23 by the lens 26 to form a subject image. The imaging element 23 converts imaging information into an electrical signal and sends the electrical signal to a control unit (not shown) of the smartphone 10.

  FIG. 5 is an exploded perspective view of the lens unit 21. The lens unit includes a cylindrical lens barrel 25, five lenses 26A to 26E, and three light shielding plates 27A to 27C. As the lens 26, various lenses such as a convex lens and a concave lens can be used. The curved surface of the lens may be a spherical surface or an aspherical surface. The lenses 26 </ b> A to 26 </ b> E and the light shielding plates 27 </ b> A to 27 </ b> C are incorporated in the lens barrel 25, and the positions in the optical axis direction are determined by a step portion 29 provided on the inner peripheral portion of the lens barrel 25.

  As shown in FIG. 6, the light shielding plate 27 uses Al (aluminum) as a base material 30, and a moth-eye structure having a fine uneven structure 31 made of Ni (nickel) is formed on the surface of the light shielding plate 27. 32 is formed. The fine concavo-convex structure 31 is formed by arranging a plurality of conical protrusions with thin tips and thick roots. In the moth-eye structure, the volume ratio between the material of the protrusion and the light medium that occupies between adjacent protrusions gradually changes from the tip of the protrusion toward the root, so the apparent refractive index changes slowly. . Therefore, light incident on the fine concavo-convex structure 31 is less likely to be reflected or refracted and is absorbed by the fine concavo-convex structure 31. Here, the light medium is air when the fine concavo-convex structure 31 is present in the atmosphere outside the lens, and is a lens material when it is present in the lens.

  The average period of the fine concavo-convex structure 31 is smaller than ½ of the shortest wavelength λA in the wavelength band of light shielded by the light shielding plate 27. Here, the period of the fine concavo-convex structure 31 is a distance between vertices (Crest) of adjacent convex portions or a root (Root), and is a distance indicated by PS1 in FIG. The average period is obtained by observing the cross section of the fine concavo-convex structure 31 with a scanning electron microscope (SEM), measuring 10 distances between the tops of 11 adjacent concavo-convex parts or valley bottoms, and calculating the average value. Can be obtained by calculating. The wavelength band of light to be shielded is 360 to 830 nm (visible light region) if the camera module 20 is a normal camera module, and 700 to 2500 nm if the camera module 20 is an infrared camera module.

  The antireflection part 32 is provided at least at a part of the part where the light is incident while being incorporated in the lens barrel 25, but may be provided at the whole part where the light is incident, or the entire surface of the light shielding plate 27. May be provided. When the fine concavo-convex structure 31 has the average period as described above, the antireflection part 32 has an increased refractive index from the surface toward the inside, and can reduce light reflection on the surface of the antireflection part 32. It is possible to prevent the light reflected on the surface of the antireflection part 32 from entering the image sensor 23 and reduce the occurrence of ghosts and flares.

  The fine concavo-convex structure 31 is formed by plating Ni (nickel) on an Al (aluminum) base material 30. As a nickel plating process for forming the fine concavo-convex structure 32, for example, a black plating technique of Ebina Denka Kogyo is used (see http://www.ebinadk.com/technology/tech/detail02.html). The fine concavo-convex structure 31 is formed by applying an energy curable resin on a base material, embossing the applied energy curable resin with a mold on which a fine concavo-convex structure is formed, and then irradiating ultraviolet rays or the like. The energy curable resin may be cured by heating or curing.

  The effect | action of the light-shielding plate of this embodiment is demonstrated using FIG. As described above, since the antireflection portion 32 of the light shielding plate 27 has the fine concavo-convex structure 31, the refractive index gradually increases from the surface toward the inside, so that the reflected light on the surface of the antireflection portion 32 is reduced. be able to. As the camera module 20 becomes thinner (lower profile), a light beam having a large incident angle θ formed by the normal V of the light shielding plate 27C and the light beam L incident on the light shielding plate 27C also enters the light shielding plate 27C. It becomes like this. Specifically, as shown in FIG. 4, when the distance from the most object-side portion of the surface of the lens 26A to the image sensor is TTL (mm) and the combined focal length f (mm) of the lenses 26A to E is used. When TTL / f ≦ 1.3, the tendency becomes remarkable.

  By the way, as a method of reducing the reflected light on the surface of the light shielding plate, as in the present invention, in addition to a method of increasing the refractive index from the surface of the light shielding plate toward the inside, a method of scattering light on the surface of the light shielding plate, Conventionally, there is a method using light interference.

  FIG. 12 shows a light shielding plate 40 in which a concavo-convex structure 41 having a larger wavelength than the wavelength of light to be shielded on the surface is formed on a base material 42. When a light beam having a small incident angle is incident on the light shielding plate 40, the light is scattered by the action of the concavo-convex structure 41, and unnecessary light incident on the image sensor can be reduced. However, when a light beam having a large incident angle is incident, the light shielding plate 40 appears to shine white when observed with the naked eye, and the unnecessary light cannot be sufficiently reduced. Here, the unnecessary light refers to harmful light that is generated by reflection from the lens surface or the like and causes flare or ghost.

  FIG. 13 shows a light shielding plate 50 having an antireflection film 51 utilizing light interference on a base material 52. In the light shielding plate 50, the optical path difference Δl between the light L1A reflected by the surface of the antireflection film 51 and the light L1B reflected by the interface between the antireflection film 51 and the base material 52 when the light L1 enters the antireflection film 51. (Nm) is Δl = 2D / cos θ, where D (nm) is the thickness of the antireflection film 51. When Δl is ½ of the wavelength λnm of the incident light, the phases of L1A and L1B are shifted by 180 °, so that the intensities are reduced and the antireflection effect is maximized. Therefore, the film thickness D of the antireflection film is generally provided as D = 4 / λ when θ is small. However, when the film thickness D is set to d = 4 / λ in this way, when a light beam having a large θ is also incident on the light shielding plate 50, the optical path difference greatly deviates from λ / 2. It cannot be obtained, and unnecessary light cannot be reduced sufficiently.

  On the other hand, in the method of increasing the refractive index from the surface of the light shielding plate toward the inside as in the present invention, the change in the antireflection effect due to the incident angle is small, and the reflection of light on the surface of the antireflection part 32 is reduced. Therefore, it is suitable as a method for preventing reflection of a light shielding plate used in a thin camera module in recent years.

"Second embodiment"
In the first embodiment, the light shielding plate 27 having the fine concavo-convex structure 31 on the surface is used, but a light shielding plate having a plurality of layers on the base material can also be used. In the light shielding plate 60 shown in FIG. 8, a base material 62 is provided with an antireflection portion 61 including a black paint layer 63 and an antireflection layer 64. In the present embodiment, the black paint layer 63 is provided by applying GT20 manufactured by Canon Kasei Co., Ltd. to the base material 62 and then drying it. The antireflection layer 64 is an Al2O3 layer provided by a vacuum deposition method. J, A.M. When the refractive index was measured using an ellipsometer VASE manufactured by Woollam Japan, the refractive index of the black paint layer 63 was 1.7 when the wavelength was 546 nm, and the refractive index of the antireflection layer 64 was 1. when the wavelength was 546 nm. 4. Thus, by providing a plurality of layers and increasing the refractive index of the antireflection part 61 provided on the light shielding plate 60 from the surface toward the inside, the reflection of light on the surface of the antireflection part 64 is reduced. be able to.

“Third Embodiment”
As yet another embodiment, a light shielding plate having a rough concavo-convex structure and a fine concavo-convex structure may be used. The light shielding plate 70 shown in FIG. 9 is formed on a base material 72 having a rough concavo-convex structure 74 having an average period longer than the longest wavelength in the wavelength band of light to be shielded, and the rough concavo-convex structure 74. And an antireflection portion 71 having a fine concavo-convex structure 73.

  Here, the base material 72 is made of Al (aluminum), and the rough concavo-convex structure 74 is formed by subjecting the base material 72 to nitric acid electrolysis. The fine uneven structure 73 is formed by Ni plating.

  The rough concavo-convex structure 74 may be formed by sandblasting. The fine concavo-convex structure 73 is formed by applying an energy curable resin on the base material, pressing the energy curable resin applied using a mold in which a fine concavo-convex structure is formed, and then irradiating ultraviolet rays or the like. It may be formed by heating or curing the energy curable resin.

  The rough concavo-convex structure 74 has an average period longer than the longest wavelength λB in the wavelength band of light that the light shielding plate 70 shields. Here, the period is the distance between the apexes of adjacent convex portions of the rough concavo-convex structure 74, and is the distance indicated by PL shown in FIG. The wavelength band of light to be shielded is 360 to 830 nm (visible light region) if the camera module 20 is a normal camera module, and 700 to 2500 nm if the camera module 20 is an infrared camera module.

  The average height of the rough concavo-convex structure 74 is ½ or more of λB. Here, the height of the rough concavo-convex structure is the height indicated by HL in FIG. 9, and the average height is a cross-section of the rough concavo-convex structure 74 observed with a scanning electron microscope (SEM). Then, it can be obtained by measuring the heights of the vertices (Crest) of the ten adjacent irregularities and calculating the average value thereof. Since the rough concavo-convex structure 74 has such a concavo-convex structure, the fine concavo-convex structure 73 described later is less likely to be peeled off from the base material, and light reflection on the surface of the antireflection portion 71 is further reduced. can do.

  The fine concavo-convex structure 73 is a moth-eye structure formed by Ni plating, and the average period of the fine concavo-convex structure 73 is smaller than ½ of the shortest wavelength λA in the wavelength band of light shielded by the light shielding plate 70. It has become. Here, the wavelength band of light to be blocked is visible light of 360 to 830 nm if the camera module 20 is a normal camera, and 700 to 2500 nm if the camera module 20 is an infrared camera. The period of the fine concavo-convex structure 73 is the distance between adjacent convex portions of the fine concavo-convex structure 73, that is, the distance indicated by PS2 in FIG. 9, and the average period is the cross section of the fine concavo-convex structure 73 taken by a scanning electron microscope. It can be obtained by observing with a scanning electron microscope (SEM), measuring 10 distances between 11 concavo-convex vertices (Crest) or between roots (Root), and calculating an average value thereof. . The average height of the fine concavo-convex structure 73 is ½ or more of the above λB. Here, the height of the fine concavo-convex structure 73 is the height indicated by HS in FIG. 9, and the average height is obtained by observing a cross section of the fine concavo-convex structure 31 with a scanning electron microscope (SEM). It can be obtained by measuring the heights of the tops (Crest) of 10 adjacent irregularities and calculating the average value thereof.

  Since the fine concavo-convex structure 73 has the concavo-convex size as described above, the reflection of light on the surface of the antireflection portion 71 can be further reduced.

“Fourth Embodiment”
In the camera module of the present invention, the following lens and light shielding plate can be used instead of the lens 26A and the light shielding plate 27A. A lens 80 shown in FIG. 10 includes a light shielding plate 81. Further, the light shielding plate 81 has an antireflection portion (not shown), and the antireflection portion is provided with a fine uneven structure and a rough uneven structure (not shown).

  A method of creating such a lens 80 will be described with reference to FIG. First, the light shielding plate 81 is temporarily assembled on the first preform 82 made of a transparent resin, and is put into the mold unit 90 (A). Next, the second preform 83 made of a transparent resin is put into the mold unit 90 and disposed so as to overlap the first preform 82 (B). In this state, the first mold 91 and the second mold 92 are heated by a heater (not shown), and the first preform 82 and the second preform 83 are heated to the glass transition temperature Tg.

  After the heating, the first preform 82 and the second preform 83 are compression molded by the first mold 91 and the second mold 92 (C). After the compression molding, the first preform 82 and the second preform 83 are cooled while maintaining the pressure. The molded shape is fixed by cooling while maintaining the compression state. The first preform 82 is integrated with the second preform 83 in a state in which the light shielding plate 81 is sandwiched between the first preform 82 and the second preform 83. After compression molding, the molded lens 80 is taken out from the mold unit 90 (D).

  As described above, since the light shielding plate 81 is included in the lens 80, a fine concavo-convex structure that is easily damaged is not exposed on the surface, and the handling becomes easy.

  In this embodiment, the lens 80 including the light shielding plate 81 is illustrated as an alternative to the lens 26A and the light shielding plate 27A. However, the light shielding plate can be included in an arbitrary lens. For example, the lens 26E includes the light shielding plate. 27C may be included.

  In this embodiment, a transparent resin is used as the lens preform. However, the present invention is not limited to this. For example, glass or a resin that transmits infrared rays and does not transmit visible light may be used. .

  In each of the above embodiments, an example in which the antireflection part is provided on a part of the light shielding plate is illustrated, but the present invention is not limited to this, and the antireflection part is provided on the entire surface of the light shielding plate. May be.

  In the said embodiment, although the smart phone 10 is illustrated as an electronic device, this invention is not restricted to this, What is necessary is just an electronic device in which a camera module is used. In particular, it is suitable for a portable electronic device that requires a thin camera module, such as a smartphone 10, a tablet terminal, a glasses-type wearable terminal, and a wristwatch-type wearable terminal.

  The present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention. For example, the above-described various embodiments and various modifications can be appropriately combined.

10 Smartphone (electronic equipment)
26, 80 Lens 27, 60, 70, 81 Light-shielding plate 20 Camera module 21 Lens unit 23 Image sensor 32, 61, 71 Antireflection part 31, 73 Fine uneven structure 74 Coarse uneven structure 30, 72 Base material

Claims (4)

A camera module having a plurality of lenses and at least one light shielding plate stacked in the optical axis direction of the lens, and an image sensor that images a subject through the lens unit;
At least a part of the light shielding plate is provided with an antireflection portion whose refractive index increases from the surface of the light shielding plate toward the inside of the light shielding plate,
Of the surfaces of the plurality of lenses, TTL / f ≦ 1.3, where TTL is the distance from the most object-side portion to the image sensor and f is the combined focal length of the lens unit ,
The antireflection portion is
A rough concavo-convex structure having an average period larger than the longest wavelength λB in the wavelength band of light to be shielded;
On the rough concavo-convex structure, there is a moth-eye structure that is a fine concavo-convex structure having an average period smaller than 1/2 of the shortest wavelength λA in the wavelength band of light to be shielded,
The light shielding plate has a base material made of Al, the base material has the rough concavo-convex structure,
The camera module according to claim 1, wherein the fine uneven structure is made of Ni plating . The camera module according to claim 1 , wherein an average height of the fine concavo-convex structure is ½ or more of λB. The camera module according to claim 2 , wherein an average height of the rough concavo-convex structure is ½ or more of λB. The camera module according to claim 1, wherein the light shielding plate is included in the lens.

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