JP2021036284A - Lens with film, lens unit, and camera module - Google Patents

Abstract

To provide a lens with film, a lens unit, and a camera module not having a reflection prevention film on a lens surface receive adverse effect from heat from a heater warming the lens.SOLUTION: A lens unit 11 of this invention is provided with a lens with film 13 provided on an end unit on an object side of a lens barrel 12 as well as having a reflection preventing film 30 formed on a surface. The reflection preventing film 30 is formed by alternately laminating a first film formed from first material having a first index of refraction and a second film formed from second material having the second index of refraction greater than the first index of refraction, and the first material and the second material have thermal shock resistance of 500°C or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lens with a film, a lens unit and a camera module, and more particularly to a lens with a film, a lens unit and a camera module which can be provided in an in-vehicle camera mounted on a vehicle such as an automobile.

In recent years, in-vehicle cameras have been installed in automobiles to support parking and to prevent collisions by image recognition, and attempts have been made to apply them to automatic driving. In addition, a camera module of such an in-vehicle camera generally includes a lens group in which a plurality of lenses are arranged along an optical axis, a lens barrel that accommodates and holds the lens group, and a lens at least one part of the lens group. A lens unit having an aperture member arranged between them is provided (see, for example, Patent Document 1).

The lens unit (camera module) having the above configuration can be used not only in an in-vehicle camera but also in various optical devices, but especially when it is exposed to an external environment in a cold region, the lens freezes or snow is attached to the lens. Since it can be assumed, it is generally equipped with a snow melting function and the like. Specifically, for example, as shown in FIG. 5, the lens group L housed and held in the lens barrel 120 is located closest to the object and is exposed from the lens barrel 120 (exposed to the external environment). In order to warm the first lens 101, the heater 130 is between the surface 101a of the first lens 101 facing the image side and the surface 102a of the second lens 102 adjacent to the first lens 101 facing the object side. For example, a PTC (positive temperature coefficient) heater is inserted.

Japanese Unexamined Patent Publication No. 2013-231993

By the way, in the lens unit provided with such a heater 130, the heat generated from the heater 130 may adversely affect the antireflection film on the lens surface. That is, the first film formed from the vapor-deposited material having the first refractive index and the second film formed from the vapor-deposited material having a second refractive index higher than the first refractive index are alternately alternated. In a general antireflection film formed by laminating, a ceramic material (SiO ₂ or Al ₂ O ₃ or the like) or a titanium-based material (TiO ₂ or the like) is often used. For example, the first film is SiO ₂ The second film is _{made of a material containing Al 2} O ₃ or TiO ₂ as a main component, and the first lens 101 in which such a reflective film receives the heat of the heater directly. When provided on the surface of the film, the antireflection film repeatedly receives heat from the heater, resulting in deterioration of the film structure and susceptibility to damage.

In particular, it is known that when a ceramic material is repeatedly subjected to a thermal shock for a long period of time even if the temperature difference is relatively low, the material deteriorates due to thermal shock fatigue and damage such as cracks occurs. Although the temperature of the first lens 101 generally reaches only about 120 ° C. due to 130, the ceramic material of the antireflection film that repeatedly receives heat of such temperature for a long period of time has high thermal shock resistance SiO _{2. Apart from that, even in Al 2} O ₃ having a thermal shock resistance exceeding this temperature, it is inevitable that cracks or the like will occur on the surface. Such cracks can adversely affect the optical properties of the lens unit and must be reliably prevented.

The present invention has been made in view of the above circumstances, and provides a lens with a film, a lens unit, and a camera module that prevent the antireflection film on the lens surface from being adversely affected by the heat of a heater that warms the lens. With the goal.

In order to solve the above problems, the present invention is a lens with a film provided at the end of the lens barrel on the object side and having an antireflection film formed on the surface thereof.
The antireflection film is formed of a first film formed of a first material having a first refractive index and a second material having a second refractive index higher than the first refractive index. It is made up of alternating layers of the second film.
The first material and the second material are characterized in that their thermal shock resistance is 500 ° C. or higher.

The present inventors have largely contributed to the thermal shock resistance of the material forming the antireflection film as a cause of the snow melting heater that repeatedly heats the lens over a long period of time adversely affecting the antireflection film on the lens. As a result of repeating various experiments, especially in a snow melting heater that heats a lens to about 120 ° C., an antireflection film is formed from a first material having a first refractive index. When the first film and the second film formed from the second material having a second refractive index higher than the first refractive index are alternately laminated, the first and second films are used. It has been found that when the thermal impact resistance of the material is 500 ° C. or higher, the antireflection film can be prevented from being damaged due to deterioration over time due to the heat of the heater, and the film strength can be maintained at a desired strength.

That is, according to the above configuration of the present invention, since the heat impact resistance of the first and second materials forming the antireflection film is 500 ° C. or higher, the lens with the film having the antireflection film is a heater (particularly). Even if it is used together with a snow melting heater that heats the lens to about 120 ° C. and repeatedly receives heat from the heater for a long period of time, it is possible to prevent the antireflection film from being adversely affected. This is the first and second ceramic materials, which can deteriorate due to thermal shock fatigue and cause damage such as cracks when repeatedly subjected to thermal shock for a long period of time, even if the temperature difference is relatively low. It can be beneficial when used as a material.

In the above configuration, the thermal shock resistance of the material shall be evaluated and measured according to the "thermal shock test method for fine ceramics" specified in JIS R1648: 2002. Further, in the above configuration, the antireflection film is provided on the surface of the lens with a film facing at least the object side, but may be provided on the surface of the lens with a film facing the image side. Further, in the above configuration, the lens with a film may be made of glass or resin.

Further, in the above configuration of the present invention, when a ceramic material is used as the first and second materials, the first material is _{mainly composed of SiO 2} and the second material is mainly composed of _{Si 3} N _4. It is preferable to use it as an ingredient. _{According to this, the heat of the heater can be efficiently transferred by using Si 3} N ₄ having particularly good thermal conductivity. For example, when the heater melts the snow on the surface of the lens with a film, the snow melts. It is possible to shorten the time.

Further, in the above configuration of the present invention, it is preferable that a hydrophilic film is provided on the antireflection film. In this way, if a hydrophilic film is provided on the antireflection film instead of a water-repellent film, the hydrophilic film is formed especially when a lens with a film is used together with a snow melting heater and the heater melts the snow on the surface of the lens with a film. Due to the hydrophilic action of the film, the snow melting time can be shortened and the visibility of the lens with a film can be improved as compared with the water-repellent film. That is, if a water-repellent film is provided on the antireflection film, the spheroidization of the water droplets is promoted under the water-repellent action, so that the water droplets having a small area are heated by the heater, and the heat transfer area is limited and heated. The efficiency decreases and the snow melting time becomes longer, but if a hydrophilic film is provided on the antireflection film, fine water droplets adhering to the lens surface under hydrophilic action spread over the hydrophilic film with high surface free energy to form a thin water film. Therefore, since the water film having a large area is heated by the heater, the heat transfer area is expanded, the heating efficiency is increased, and the snow melting time can be shortened. Further, according to the hydrophilic film, water droplets that reduce visibility are spread in a film shape, so that visibility can be improved.

The hydrophilic film can be formed by, for example, vapor deposition, coating, spraying, dipping method or the like with or without masking by taping, but from the viewpoint of increasing the adhesion strength of the film, the hydrophilic film is vapor-deposited. It is preferable to form by. In particular, when a hydrophilic film is provided on the antireflection film by vapor deposition, it can contribute to improving the adhesion of the hydrophilic film to the lens surface, especially when the lens is a glass lens. That is, in general, when a hydrophilic film is formed directly on the lens surface, it is necessary to match the composition of the entire hydrophilic film with that of the lens in order to improve the adhesion between the lens surface and the hydrophilic film, which is troublesome. In addition to this, although it is costly, when a hydrophilic film is formed on the lens surface via an antireflection film as in the above configuration of the present invention, SiO _2, which is a general component of the antireflection film, is antireflection. Since it is present at the interface between the film and the hydrophilic film, the compatibility between the hydrophilic film and the antireflection film is good, and therefore the adhesion is improved only at the interface between the antireflection film and the glass surface. It is only necessary to modify the composition for the purpose. Therefore, the same adhesive force can be stably realized by always using the hydrophilic film with the same specifications without much labor and cost.

Further, in the above configuration, the hydrophilic film is a thin film having hydrophilicity, and the contact angle of water droplets with the hydrophilic film is 40 degrees or less. On the other hand, the water-repellent film is a thin film having water repellency, which means that the contact angle of water droplets with the water-repellent film is 90 degrees or more, and is distinguished from the hydrophilic film in this respect. In this case, the contact angle shall be measured by the intravenous drop method (A, half-angle, Method), and the lens surface on which the film is formed is 2.5 microliters so as not to be affected by the lens surface. Water droplets are dropped, and the curved surface connecting the left and right end points of the droplets is regarded as a straight line, and the contact angle of the water droplets is measured.

Further, the present invention is a lens unit including a lens group in which a plurality of lenses are arranged along the optical axis of the lens and a lens barrel in which the lens group is housed.
A lens with a film having the above configuration is provided in the opening on the object side of the lens barrel, and between the surface of the lens with the film facing the image side and the surface of the lens adjacent to the lens with the film facing the object side. It is characterized in that a heater is inserted in the lens.

As described above, when the lens with a film having the above configuration is used together with a heater, it can exhibit its original characteristics and exhibit the above-mentioned excellent effects.
In the above configuration of the present invention, examples of the "heater" include a PTC (positive temperature coefficient) heater. Further, in the above configuration, when the lens with a film adjacent to the heater is a glass lens, the surface facing the image side may be blacked out to prevent light shielding and ghosting.

The present invention also provides a camera module including the lens unit. Such a camera module can also obtain the same effects as the above-mentioned lens with film and lens unit.

According to the present invention, since the heat impact resistance of the first and second materials forming the antireflection film is 500 ° C. or higher, a lens with a film having the antireflection film is used together with the heater to generate heat from the heater. It is possible to prevent the antireflection film from being adversely affected even if it is repeatedly subjected to the above.

It is the schematic sectional drawing of the lens unit which concerns on one Embodiment of this invention which includes a heater. It is the schematic which shows typically the laminated structure of the antireflection film of the lens with a film of the lens unit of FIG. (A) is a schematic view schematically showing how heater heat is transferred when a water-repellent film is provided on the antireflection film, and (b) is a schematic diagram when a hydrophilic film is provided on the antireflection film. It is the schematic which shows the way of transfer of a heater heat schematically. FIG. 5 is a schematic cross-sectional view of a camera module including the lens unit of FIG. It is the schematic sectional drawing of the conventional lens unit provided with a heater.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The lens unit of the present embodiment described below is particularly for a camera module such as an in-vehicle camera. For example, the lens unit is fixedly installed on the outer surface side of an automobile, and wiring is drawn into the automobile. Connected to a display or other device. Further, in FIGS. 1 to 5, hatching is omitted for a plurality of lenses except for the first lens.

FIG. 1 shows a lens unit 11 according to an embodiment of the present invention including a heater. As shown in the figure, the lens unit 11 of the present embodiment includes, for example, a metal cylindrical lens barrel (barrel) 12 and a plurality of lenses arranged in the stepped inner accommodation space S of the lens barrel 12. For example, from the object side, four lenses including a first lens 13, a second lens 14, a third lens 15, and a fourth lens 16 and an aperture member 22 are provided. In the present embodiment, the diaphragm member 22 is inserted between the third lens 15 and the fourth lens 16, limits the amount of transmitted light, and determines the F value as an index of brightness. It is an "aperture diaphragm" or a "light-shielding diaphragm" that blocks light rays that cause ghosts and light rays that cause aberrations. An in-vehicle camera including such a lens unit 11 includes a lens unit 11, a substrate having an image sensor (not shown), and an installation member (not shown) for installing the substrate in a vehicle such as an automobile.

A plurality of lenses 13, 14, 15, and 16 incorporated and held in the inner accommodation space S of the lens barrel 12 are stacked and arranged so that their optical axes are aligned with each other, and one light. Each lens 13, 14, 15, 16 is arranged along the axis O to form a group of lens groups L used for imaging. In particular, in the present embodiment, the first lens 13 is a spherical glass lens, and the second lens 14, the third lens 15, and the fourth lens 16 are resin lenses, respectively. Not limited to. For example, the second to fourth lenses may be glass lenses, and the first lens and the lens barrel 12 may be made of resin. The first lens 13 provided at the end (opening) of the lens barrel 12 on the object side is a lens with a film having an antireflection film and a hydrophilic film, as will be described later. Therefore, in the following, the first lens 13 may be referred to as a lens with a film. The second lens 14, the third lens 15, and the fourth lens 16 are also provided with an antireflection film.

A cap 23 is screwed to the end (upper end in FIG. 1) of the lens barrel 12 on the object side, and the first lens 13 positioned on the object side of the lens group L by the cap 23 is the lens barrel. It is fixed to the end of 12 on the object side. Of course, when the lens barrel 12 is made of resin, the first lens 13 is attached to the object-side end of the lens barrel 12 by caulking the end of the lens barrel 12 on the object side in the radial direction. It may be fixed.

Further, an inner flange portion 24 having an opening having a diameter smaller than that of the fourth lens 16 is provided at the image-side end portion (lower end portion in FIG. 1) of the lens barrel 12. The inner flange portion 24 and the cap 23 hold and fix the plurality of lenses 13, 14, 15, 16 and the diaphragm member 22 constituting the lens group L in the lens barrel 12 in the optical axis direction.

An O-ring 26 as a sealing member is provided between the outer peripheral annular portion of the surface 13b facing the image side of the first lens 13 located on the most object side and the lens barrel 12, and the lens barrel is sandwiched between them. It is in a state of being sealed at the end on the object side of the twelve. This prevents fine particles such as water and dust from entering the lens barrel 12 from the end of the lens unit 11 on the object side. On the outer peripheral surface of the lens barrel 12, an outer flange portion 25 used when the lens barrel 12 is installed in the in-vehicle camera is provided on the outer peripheral surface of the lens barrel 12 in a flange shape.

Further, in the present embodiment, the image side of the first lens 13 is warmed as necessary (for the purpose of melting snow or the like) of the first lens 13 exposed from the lens barrel 12 (exposed to the external environment). An annular heater 40 is interposed between the surface 13b facing the surface and the surface 14a of the second lens 14 adjacent to the first lens 13 facing the object side. In particular, in the present embodiment, the heater 40 is formed as a PTC (positive temperature coefficient) heater, and heats the first lens 13 to, for example, about 120 ° C. The heater 40 is supplied with power from a power source (not shown) via the lead wire 73.

Further, in the present embodiment, the antireflection film 30 is provided on the concave portion of the surface 13a facing the object side and the surface 13b facing the image side of the first glass lens 13, respectively. These antireflection films 30 are provided over at least the effective diameter range of the first lens 13. Further, a hydrophilic film 32 is further provided on the antireflection film 30 provided on the lens surface 13a facing the object side. Although not clearly shown, the portion of the surface 13b of the first lens 13 that is in adjacent contact with the heater 40 and faces the image side is subjected to blackening treatment for shading and preventing ghosting.

As is clearly shown in FIG. 2, the antireflection film 30 provided on the surfaces 13a and 13b of the first lens 13 as a lens with a film (in FIG. 2, the antireflection film 30 provided on the surface 13a is provided. The hydrophilic film 32) is formed from _{SiO 2} as a first material having a first refractive index, or a first film formed from a first material containing _{SiO 2 as a main component. It is formed from 30b and Si 3} N ₄ as a second material having a second refractive index higher than the first refractive index, or from a second material containing Si ₃ N ₄ as a main component. The second film 30a is alternately laminated and formed on the surfaces 13a and 13b of the first lens 13, for example, by vapor deposition. Here, for example, the first material is a low refractive index material having a refractive index of 1.46, and the second material is a high refractive index material having a refractive index of 2.02. In this case, SiO ₂ which is the first material has a thermal shock resistance exceeding 1000 ° C., and Si ₃ N ₄ which is a second material has a thermal shock resistance of 600 to 650 ° C. doing. Furthermore, each membrane 30a, respectively 30b the thickness of, SiO ₂ layer (first film 30b) is 5nm~150nm, _Si 3 _{N 4} layers (second layer 30a) and has a 5 nm to 100 nm. In particular, the antireflection film 30 of the present embodiment is formed by laminating six layers as a whole, and the total thickness is set to 240 nm.
In FIG. 2, the surface 13a of the lens 13 is followed by the second film 30a and then the first film 30b, but the second film 30a and the first film 30b are laminated. It does not matter if they are replaced. Specifically, the lens surface 13a / first film 30b / second film 30a / first film 30b / second film 30a / ... may be configured as the optimum thickness.

Further, FIG. 4 is a schematic cross-sectional view of the camera module 300 of the present embodiment having the lens unit 11 having the above-described configuration in which the filter 100 is attached. As shown in the figure, the camera module 300 includes an upper case (camera case) 301, which is an exterior component, and a mount (pedestal) 302 that holds the lens unit 11. Further, the camera module 300 includes a seal member 303 and a package sensor (image sensor) 304.

The upper case 301 is a member that exposes the end portion of the lens unit 11 on the object side and covers the other portion. The mount 302 is arranged inside the upper case 301 and has a female screw 302a that is screwed with the male screw 11a of the lens unit 11. The seal member 303 is a member inserted between the inner surface of the upper case 301 and the outer peripheral surface 12a of the lens barrel 12 of the lens unit 11 in a state of being placed on the outer flange portion 25, and is a member of the upper case 301. It is a member for maintaining the airtightness inside.

The package sensor 304 is arranged inside the mount 302 and is arranged at a position where it receives an image of an object formed by the lens unit 11. Further, the package sensor 304 includes a CCD, CMOS, and the like, and converts the light that is focused and reaches through the lens unit 11 into an electric signal. The converted electrical signal is converted into analog data or digital data, which are components of image data captured by the camera.

As described above, according to the present embodiment, _{the heat impact resistance of the first and second materials (SiO 2} , Si ₃ N ₄ ) forming the antireflection film 30 is 500 ° C. or higher. Even if the lens 13 with a film having the antireflection film 30 repeatedly receives the heat from the heater 40 for a long period of time, it is possible to prevent the antireflection film 30 from being adversely affected. This is a ceramic, as in the present embodiment, in which the material may deteriorate due to thermal shock fatigue and damage such as cracks may occur when the material is repeatedly subjected to thermal shock for a long period of time even if the temperature difference is relatively low. It can be beneficial when the material is used as the first and second materials.

_{Further, in the present embodiment, since Si 3} N ₄ having good thermal conductivity is used as the second material of the antireflection film 30, the heat of the heater 40 can be efficiently transferred, and the heater 40 can transfer the heat. When the snow on the surface of the lens 13 with a film is melted, the snow melting time can be shortened.

Further, in the present embodiment, since the hydrophilic film 32 is provided on the antireflection film 30 instead of the water-repellent film, the snow melting time is shortened as compared with the water-repellent film due to the hydrophilic action of the hydrophilic film 32. At the same time, the visibility of the film-attached lens 13 can be improved. That is, when the water-repellent film 150 is provided on the antireflection film 30 as shown in FIG. 3A, the water droplets 80 are promoted to be spheroidized under the water-repellent action, so that the water droplets 80 having a small area are heated by the heater 40. (In FIG. 3, the heat transfer direction is indicated by an arrow), the heat transfer area is limited, the heating efficiency is lowered, and the snow melting time is lengthened. When the hydrophilic film 32 is provided on the antireflection film 30 as shown, fine water droplets adhering to the surface of the lens 13 spread over the hydrophilic film having high surface free energy under the hydrophilic action to form a thin water film 82. By heating the water film 82 having a large area by the heater 40, the heat transfer area is expanded, the heating efficiency is increased, and the snow melting time can be shortened. Further, according to the hydrophilic film 32, the water droplet 80 that reduces the visibility is spread in a film shape, so that the visibility can be improved.

Although the present invention has been described above in relation to a specific embodiment, the present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the gist thereof. For example, in the present invention, the shape of the lens, the lens barrel, and the like, the antireflection film, and the form of the heater are not limited to the above-described embodiments. Further, a part or all of the above-described embodiments may be combined within a range that does not deviate from the gist of the present invention, or a part of the configuration may be omitted from one of the above-described embodiments. May be good.

11 Lens unit 12 Lens barrel 13 First lens 14 Second lens 30 Antireflection film 32 Hydrophilic film 40 Heater 300 Camera module L Lens group O Optical axis

Claims (5)

A lens with a film that is provided at the end of the lens barrel on the object side and has an antireflection film formed on the surface.
The antireflection film is formed of a first film formed of a first material having a first refractive index and a second material having a second refractive index higher than the first refractive index. It is made up of alternating layers of the second film.
The first material and the second material are lenses with a film, which have a thermal shock resistance of 500 ° C. or higher. The lens with a film according to claim 1, wherein the first material _{contains SiO 2} as a main component, and the second material _{contains Si 3} N _{4 as a main component.} The lens with a film according to claim 1 or 2, wherein a hydrophilic film is provided on the antireflection film. A lens unit including a lens group in which a plurality of lenses are arranged along the optical axis of the lens and a lens barrel in which the lens group is housed.
The lens with a film according to any one of claims 1 to 3 is provided in the opening on the object side of the lens barrel, and the surface of the lens with a film facing the image side and a lens adjacent to the lens with the film. A lens unit characterized in that a heater is inserted between the lens and the surface of the lens facing the object side. A camera module including the lens unit according to claim 4.

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