JP7614722B2 - Lens units and camera modules - Google Patents

Description

The present invention relates to a lens unit and a camera module that can be used to configure an on-board camera mounted on a vehicle such as an automobile.

Conventionally, automobiles have been equipped with on-board cameras to assist with parking and prevent collisions through image recognition, and there are also attempts to apply this to autonomous driving. Camera modules such as on-board cameras generally include a lens unit that has a lens group consisting of multiple lenses arranged along an optical axis, a lens barrel that houses and holds this lens group, and an aperture member that is placed between at least one of the lenses in the lens group (see, for example, Patent Document 1).

In particular, in the case of a lens unit for an in-vehicle camera, when at least a part of the lens unit is installed outside the vehicle, as shown in FIG. 7, in a state where the lens group L is assembled and housed in the inner housing space S of the lens barrel 102, an O-ring 104 is interposed between the first lens 100 located on the most object side of the lens group L and the lens barrel 102 to prevent water and dust from entering the lens group L inside the lens barrel 102. In this case, for example, a stepped reduced diameter portion 100b with a reduced diameter at the image side portion of the lens 100 is provided on the outer peripheral side surface 100a of the first lens 100, and an O-ring 104 is attached to this reduced diameter portion 100b, and the O-ring 104 is compressed in the radial direction between the outer peripheral side surface 100a of the first lens 100 and the inner peripheral surface 102a of the lens barrel 102, thereby sealing the object side end of the lens barrel 102.

Furthermore, with the lens group L assembled and housed in the inner housing space S of the lens barrel 102, the crimped portion 123 at the object side end (the upper end in FIG. 7) is crimped radially inward, thereby fixing the first lens 100 to the object side end of the lens barrel 102 by this crimped portion 123.

JP 2013-231993 A

However, even if waterproofing is implemented using the O-ring 104 as described above, moisture (water vapor) can enter the lens unit through various routes. Therefore, when the difference between the outside air temperature and the temperature inside the lens unit becomes large, the water vapor inside the lens unit condenses and condensation occurs on the lens surface. In particular, condensation is likely to occur on the back surface 100c of the first lens 100 in the inter-lens space S1 between the first lens 100 and the adjacent second lens 101, which is most affected by the temperature difference with the outside.

The causes of the large difference between the outside air temperature and the temperature inside the lens unit include the temperature inside the lens unit rising in winter when the outside air is cold, the temperature inside the lens unit rising due to heat transferred from an image sensor (image pickup element) that is always powered to receive the light focused through the lens unit and convert it into an electrical signal, or the first lens 100 being cooled when the surface 100d of the first lens 100 is exposed to rain or splashed with water from a puddle on the road while the temperature inside the lens unit is high due to heat from the image sensor or the surrounding environment (for example, the engine of a vehicle).

In addition, examples of paths that allow water vapor to enter the lens unit include a path that runs from the gap between the crimped portion 123 of the lens barrel 102 and the first lens 100 through a portion of the periphery of the O-ring 104 and the gap between the first lens 100 and the lens barrel 102 and/or the second lens 101 to the inter-lens space S1, etc., or through the moisture-permeable resin that forms the lens barrel 102 and the lenses.

In any case, if water vapor enters the lens unit through such a route and a temperature difference occurs between the outside air and inside the lens unit due to the factors described above, condensation will occur in the inter-lens space S1, particularly on the back surface 100c of the first lens 100, causing the captured image to become blurred and making it impossible to obtain the desired resolution (deteriorating visibility). Therefore, it is necessary to further ensure the airtightness of the lens unit and suppress the intrusion of water vapor into the inter-lens space S1.

The present invention has been made in consideration of the above circumstances, and aims to provide a lens unit and camera module that can prevent condensation on the lens surface by suppressing the intrusion of water vapor into the inter-lens space between the lens located closest to the object and the lens adjacent to it.

In order to solve the above problems, the present invention provides a lens unit having a lens group including a plurality of lenses arranged along an optical axis, and a cylindrical lens barrel having an inner storage space for storing and holding the lens group,
the lens group includes a first lens located closest to the object side and a second lens adjacent to the first lens on the image side thereof, and opposing surfaces of the first lens and the second lens opposing each other in the optical axis direction are bonded to each other by an adhesive medium layer such that an inter-lens space between the first lens and the second lens is sealed from the outside,
The adhesive medium layer includes a first adhesive medium layer located on the first lens side and a second adhesive medium layer located on the second lens side,
The adhesive medium is characterized in that a thin plate-like intermediate material is interposed between the first adhesive medium layer and the second adhesive medium layer.

In the present invention, the opposing surfaces of the first lens and the second lens, which can be a path for allowing water vapor to enter the lens unit, are bonded with an adhesive medium layer so that the inter-lens space between the first lens and the second lens is sealed from the outside. This prevents water vapor from entering the inter-lens space, where condensation is most likely to occur, even in a high humidity environment, and further prevents water vapor from entering the lens unit on the image side (improving airtightness), reducing the amount of water vapor in the inter-lens space and suppressing condensation on the lens surfaces, particularly on the image-side surface (rear surface) of the first lens. In other words, this type of bonding between lenses ensures a highly reliable sealed state in the inter-lens space.

In particular, the opposing surfaces of the first lens and the second lens facing each other in the optical axis direction are bonded together by an adhesive medium layer, and in the present invention, the adhesive medium forming the adhesive medium layer preferably has "radial followability" (flexibility sufficient to withstand radial stress applied to the lens bonding interface after the lens expands (contracts) due to temperature changes) that can follow the relative radial displacement between the lenses caused by the difference in the amount of expansion and contraction of the lenses when the temperature changes due to the difference in the linear expansion coefficients between the lenses, and/or good "adhesion" (adhesion of the adhesive medium to the opposing surfaces of the lenses) that prevents the bonding interface between the lenses from peeling off due to the separation between the lenses in the optical axis direction caused by the increase in internal pressure in the space between the lenses in a high-temperature environment, or "optical axis followability" that can follow the separation displacement between the lenses in the optical axis direction.

In addition, the adhesive medium layer has a first adhesive medium layer located on the first lens side and a second adhesive medium layer located on the second lens side, and a thin plate-like intermediate material is interposed between the first adhesive medium layer and the second adhesive medium layer, so that the adhesive medium forming the first adhesive medium layer and the adhesive medium forming the second adhesive medium layer can be different types. Therefore, for example, when the first lens is a glass lens and the second lens is a resin lens, it is easy to select an adhesive medium that can firmly bond the glass lens (first lens) to the thin plate-like intermediate material and an adhesive medium that can firmly bond the resin lens (second lens) to the thin plate-like intermediate material.
Furthermore, since the thickness of the first adhesive medium layer and the thickness of the second adhesive medium layer can be easily set, the above-mentioned "radial followability" can be easily set and enhanced.

Examples of adhesive media that form the adhesive medium layer include acrylic and epoxy adhesives, and elastic materials having tackiness (e.g., gel-like), and such adhesive media are provided outside the effective diameter of the lens (outside the optical surface where light does not pass). These adhesive media may be used in combination or in a mixed form.
In the above configuration, it is preferable to provide a seal member between the first lens and the lens barrel. Such a seal member ensures sealing performance (waterproof performance) in the path that allows water vapor to enter the lens unit, and can contribute to forming a sealed state in the inter-lens space between the first and second lenses.
In addition, the water absorption rate of the adhesive medium forming the adhesive medium layer is preferably 5.0 wt % or less (JIS K6911 (boiling for 1 hour)). By setting the water absorption rate of the adhesive medium to a low level in this way, it is possible to effectively prevent water vapor from penetrating into the space between the lenses.

In the above configuration, the lens barrel preferably has a crimping portion for fixing, in the optical axis direction, the first lens of the lens group incorporated in the inner housing space by being crimped radially inward.
Such a crimped portion generates a force in the optical axis direction pressing the first lens against the second lens, and can contribute to the adhesion at the adhesive interface between the first and second lenses, in particular the adhesion required for the adhesive medium described above.
Note that the method is not limited to caulking, and the lens may be fixed by using a fixing cap, which is a separate member, and screwing the fixing cap in. When using a cap, it is desirable to increase the cap screwing load so that a compressive load is generated on the lens in the optical axis direction, thereby improving the adhesion of the adhesive interface between the lenses.

The "radial conformability" required for the adhesive medium described above can be achieved by setting the hardness of the adhesive medium within the Shore hardness range of A10 to A100 (Shore A hardness 10 to 100) or within the Shore hardness range of D10 to D90 (Shore D hardness 10 to 90). Furthermore, it is preferable to set it within the range of A30 to A95 or D10 to D60. In addition to or instead of setting the hardness of the adhesive medium within such a range, such "radial conformability" can also be achieved by ensuring that the thickness of the adhesive medium (layer thickness of the adhesive medium layer) is greater than or equal to a predetermined value. As a means for ensuring that the thickness of the adhesive medium is greater than or equal to a predetermined value (ensuring the radial movement of the adhesive medium layer), for example, fillers are included in the adhesive medium and the maximum length of these fillers is set to 5 to 500 μm. Depending on the orientation of the filler in the adhesive medium, if the filler extends toward the optical axis direction in the adhesive medium, the thickness of the adhesive medium layer (dimension in the optical axis direction) can be determined by the length of the extending filler.

Furthermore, the "adhesion" or "optical axis direction tracking" required for the adhesive medium described above can be achieved by setting the surface roughness of at least one of the opposing surfaces of the first and second lenses to 0.01 μm to 200 μm in terms of root-mean-square roughness Rq.
This is particularly beneficial when the first and second lenses are made of glass, for which the above-mentioned "radial tracking ability" need not be taken into consideration, because in the case of glass, there is a particular need to be concerned about peeling of the adhesive interface between the lenses due to an increase in internal pressure in the space between the lenses in a high-temperature environment.

In the above configuration, the thin plate-like intermediate object may be a light-shielding plate, a heater, or a rubber sheet.
When the thin plate-like inclusion is a light-shielding plate (e.g., a SUS plate having a thickness of 1 mm or less), a transparent or light-transmitting adhesive medium having relatively high adhesive strength (higher adhesive strength than a black adhesive) can be used as the adhesive medium to form the adhesive medium layer, and light-shielding properties can be reliably ensured.
As the black adhesive, for example, one having a light transmittance of 20% or less in the wavelength region of 450 nm to 650 nm is preferable. By making the adhesive black and suppressing its light transmittance, it is possible to omit the inking process for preventing light blocking and ghosting, but there is a risk of the adhesive strength decreasing. However, as described above, since a light blocking plate is interposed between the first adhesive medium layer and the second adhesive medium layer, it is possible to ensure light blocking properties and the like even if the black coating process is omitted, and a predetermined adhesive strength can be ensured. In addition, by not performing black coating, it is possible to suppress the intrusion of moisture from between the opposing surface of the first lens and the surface of the thin plate-like inclusion.

When the thin plate-like inclusion is a heater, the first lens and the second lens can be heated by the heater, so that condensation in the inter-lens space between the first lens and the second lens can be suppressed. Even if moisture gets mixed in due to deterioration of the adhesive medium layer, the moisture can be heated by the heater to eliminate condensation on the lens surface.
As the heater, for example, a flat ceramic heater having a thickness of about 1 to 2 mm can be used.

When the thin plate-like inclusion is a rubber sheet, the "radial tracking ability" that can follow the relative radial displacement between the lenses caused by the difference in the amount of expansion and contraction of the lenses when the temperature changes due to the difference in the linear expansion coefficient between the lenses is further improved. In other words, if there is a difference in the amount of expansion and contraction between the lenses (the first lens and the second lens), this difference can be mitigated by the rubber sheet, so that the "radial tracking ability" is further improved and peeling of the adhesive surface of the adhesive medium layer can be prevented.

In the above configuration, the opposing surfaces of the first lens and the second lens may be provided with a stopper portion that stops the adhesive medium applied to the opposing surfaces from flowing into the space between the lenses.
This preventing portion may be, for example, a recess provided in at least a portion of one of the opposing surfaces for filling with the adhesive medium, or a protrusion that prevents the adhesive medium from flowing into the space between the lenses.
According to this configuration, the flow of the adhesive medium applied to the opposing surface into the space between the lenses can be prevented by the preventing portion, and the application of the adhesive medium becomes easy.

In the above configuration, the adhesive medium forming the first adhesive medium layer and the adhesive medium forming the second adhesive medium layer may be of different types.
According to such a configuration, for example, when the first lens is a glass lens and the second lens is a resin lens as described above, an adhesive medium capable of firmly bonding the glass lens (first lens) to the thin plate-like inclusion and an adhesive medium capable of firmly bonding the resin lens (second lens) to the thin plate-like inclusion can be easily selected, so that the first lens and the second lens can be bonded more firmly.

In the above configuration, one of the first lens and the second lens may be made of glass and the other may be made of resin, or both of the first lens and the second lens may be made of resin and the difference between their linear expansion coefficients may be 40×10 ⁻⁶ /K(m) or more (a combination of lenses with different linear expansion coefficients).
As described above, when the opposing surfaces of the lenses are bonded together using an adhesive medium, the adhesive medium can have "radial tracking ability" that can follow the relative radial displacement between the lenses caused by the difference in the amount of expansion and contraction of the lenses when temperature changes due to the difference in the linear expansion coefficients between the lenses. Therefore, according to the present invention, even when lenses having different linear expansion coefficients are combined, a highly reliable sealed state can be ensured in the space between the lenses.

In the above configuration, it is preferable that the pressure in the interlens space between the first lens and the second lens is equal to or less than atmospheric pressure at room temperature of 20 degrees. In this way, if the pressure in the interlens space is equal to or less than atmospheric pressure, the internal pressure in the interlens space does not increase even in a high temperature environment, and this solves the problem of the adhesive interface between the lenses peeling off due to the separation of the lenses in the optical axis direction caused by the increase in internal pressure. Note that examples of methods for bonding the lens facing surfaces together so that the pressure in the interlens space is equal to or less than atmospheric pressure include bonding the lens facing surfaces together in a vacuum atmosphere and bonding while suctioning and degassing the interlens space.

A camera module according to the present invention includes the lens unit.
According to this configuration, the effects of the lens unit described above can be obtained in the camera module.

The present invention makes it possible to prevent condensation on the lens surface by suppressing the intrusion of water vapor into the space between the first lens located closest to the object and the second lens adjacent to it.

1 is a schematic cross-sectional view of a lens unit according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a camera module having the lens unit shown in FIG. 1 . FIG. 2 is an enlarged cross-sectional view of a main part of the lens unit shown in FIG. 1 . FIG. 2 is a cross-sectional view showing a schematic diagram of a first example of a bonding state between opposing lens surfaces. FIG. 11 is a cross-sectional view showing a schematic bonding state between opposing lens surfaces according to a second example. FIG. 11 is a cross-sectional view showing a schematic bonding state between opposing lens surfaces in a third example. FIG. 1 is a schematic cross-sectional view showing an example of a conventional lens unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The lens unit of this embodiment described below is particularly intended for use in a camera module such as an in-vehicle camera, and is fixedly installed on the outer surface of a vehicle, with wiring leading into the vehicle and connected to a display or other devices. In addition, hatching is omitted for the lenses in all figures, including the above-mentioned FIG. 7.

1 shows a lens unit 11 according to an embodiment of the present invention. As shown in the figure, the lens unit 11 of this embodiment includes a cylindrical lens barrel 12 made of, for example, resin, and a plurality of lenses arranged in a stepped inner storage space S of the lens barrel 12, for example, five lenses consisting of a first lens 13, a second lens 14, a third lens 15, a fourth lens 16, and a fifth lens 17 from the object side (the upper side in FIG. 1), and two aperture members 22a and 22b.
The first diaphragm member 22a from the object side of the two diaphragm members 22a and 22b is disposed between the second lens 14 and the third lens 15. The second diaphragm member 22b from the object side is disposed between the third lens 15 and the fourth lens 16. The diaphragm members 22a and 22b are "aperture diaphragms" that limit the amount of transmitted light and determine the F-number, which is an index of brightness, or "light blocking diaphragms" that block light rays that cause ghosts and light rays that cause aberrations. An in-vehicle camera equipped with such a lens unit 11 includes the lens unit 11, a substrate having an image sensor (not shown), and an installation member (not shown) that installs the substrate on a vehicle such as an automobile.

The lenses 13, 14, 15, 16, and 17 incorporated and held in the inner storage space S of the lens barrel 12 are stacked and arranged with their optical axes aligned, and the lenses 13, 14, 15, 16, and 17 are arranged along a single optical axis O to form a group of lenses L used for imaging. In this case, the first lens 13 that is located closest to the object and that constitutes the lens group L is a spherical glass lens having a convex surface on the object side and a concave surface on the image side, and the other lenses 14, 15, 16, and 17 are resin lenses, but are not limited to this (for example, the first lens 13 may be a resin lens; when the first and second lenses 13 and 14 are made of resin, the difference between the linear expansion coefficients of the first lens 13 and the second lens 14 may be, for example, 40×10 ⁻⁶ /K(m) or more).

The present invention, including this embodiment, is characterized in that the opposing surfaces 13a, 14a of the first lens 13 and the second lens 14 are bonded to each other by an adhesive medium layer 50 so that the inter-lens space S1 between the first lens 13 and the second lens 14 is sealed from the outside, and the number of lenses, the materials of the lenses and the lens barrel, etc. can be set arbitrarily depending on the application, etc.
In this embodiment, the fourth and fifth lenses 16 and 17 located on the image side are cemented lenses, but this is not necessary. The surfaces of these lenses 13, 14, 15, 16, and 17 may be provided with an anti-reflection film, a hydrophilic film, a water-repellent film, or the like, as necessary.

In this embodiment, an O-ring 26 serving as a seal member is interposed between the first lens 13 located closest to the object and the lens barrel 12 to prevent water and dust from entering the lens group L inside the lens barrel 12. In this case, a stepped reduced diameter portion 13e having a smaller diameter at the image side portion of the lens 13 is provided on the outer circumferential surface 13d of the first lens 13, and the O-ring 26 is attached to this reduced diameter portion 13e, and the O-ring 26 is compressed in the radial direction between the outer circumferential surface 13d of the first lens 13 and the inner circumferential surface 12a of the lens barrel 12, thereby sealing the object side end of the lens barrel 12.
In addition, the sealing member interposed between the first lens 13 and the lens barrel 12 is not limited to an O-ring 26, but may be in any form as long as it is an annular body that can seal between the first lens 13 and the lens barrel 12.

A cylindrical inner wall 12b is provided on the object side inside the lens barrel 12, and a groove 18 is formed between this inner wall 12b and the outer wall 12c, and an annular body 27 is provided inside the groove 18, with an O-ring 26 in close contact with this annular body 27. The reason for forming the groove 18 between the inner wall 12b and the outer wall 12c is to prevent large sink marks from occurring and dimensional accuracy from being affected when the resin lens barrel 12 is molded and cooled, since the wall thickness would be too thick if the inner wall 12b and the outer wall 12c were integrated without a groove.
The ring-shaped body 27 is made of a relatively soft elastic material, such as Teflon (registered trademark). The ring-shaped body 27 has the function of supporting the O-ring 26 in the optical axis direction. Since the ring-shaped body 27 is a separate member from the lens barrel 12, it is possible to change the ring-shaped body 27 to one with a different height depending on the size of the O-ring 26, and it is ensured that the O-ring 26 seals with an appropriate elastic force.

When the lens group L is assembled and housed in the inner housing space S of the lens barrel 12, the crimping portion 23 at the object side end (the upper end in FIG. 1) is thermally crimped radially inward, thereby fixing the first lens 13 located closest to the object side of the lens group L to the object side end of the lens barrel 12 in the optical axis direction by this crimping portion 23. In this case, to ensure stable crimping, the portion of the glass lens 13 where the crimping portion 23 is pressed against is formed as a flat portion 13b that is cut diagonally in a plane.

In addition, an inner flange portion 24 having an opening with a diameter smaller than that of the fifth lens 17 is provided at the end of the lens barrel 12 on the image side (the lower end in FIG. 1). The inner flange portion 24 and the crimped portion 23 hold and fix the multiple lenses 13, 14, 15, 16, and 17 and the aperture members 22a and 22b that make up the lens group L inside the lens barrel 12 in the optical axis direction.

The inner diameter of the lens barrel 12 decreases stepwise from the object side to the image surface side. Correspondingly, the outer diameters of the lenses 13, 14, 15, 16, and 17 decrease from the object side to the image surface side. Basically, the outer diameters of the lenses 13, 14, 15, 16, and 17 are approximately equal to the inner diameters of the portions of the lens barrel 12 where the lenses 13, 14, 15, 16, and 17 are supported.
An outer flange portion 25 is provided on the outer circumferential surface of the lens barrel 12 in the shape of a brim and is used when installing the lens barrel 12 on an in-vehicle camera.

Figure 2 is a schematic cross-sectional view of a camera module 300 of this embodiment having the lens unit 11 shown in Figure 1. As shown in the figure, the camera module 300 is configured to include a lens unit 11 to which a filter 105 is attached.

The camera module 300 includes an upper case (camera case) 301, which is an exterior component, and a mount (base) 302 that holds the lens unit 11. The camera module 300 also includes a sealing member 303 and a package sensor (imaging element) 304.

The upper case 301 is a member that exposes the object side end of the lens unit 11 and covers the other parts. The mount 302 is disposed inside the upper case 301 and has a female thread 302a that screws into the male thread 11a of the lens unit 11. The seal member 303 is a member that is interposed between the inner surface of the upper case 301 and the outer peripheral surface 12d of the lens barrel 12 of the lens unit 11, and is a member that maintains airtightness inside the upper case 301.

The package sensor 304 is disposed inside the mount 302, and is positioned to receive the image of the object formed by the lens unit 11. The package sensor 304 also includes a CCD, CMOS, or the like, and converts the light that is collected and reaches the package sensor 304 through the lens unit 11 into an electrical signal. The electrical signal is then converted into analog data or digital data, which is a component of the image data captured by the camera.

In the lens unit 11 and camera module 300 configured as described above, as shown in Figures 2 and 3, the first lens 13 located closest to the object side and the second lens 14 adjacent to the first lens 13 on the image side thereof each have opposing surfaces 13a, 14a that face each other in the optical axis direction, and these opposing surfaces 13a, 14a are bonded together by an adhesive medium layer 50 so that the inter-lens space S1 between the first lens 13 and the second lens 14 is sealed from the outside.

In addition, in this embodiment, the adhesive medium layer 50 has a first adhesive medium layer 51 located on the first lens 13 side and a second adhesive medium layer 52 located on the second lens 14 side, and a thin plate-shaped inclusion 55 is interposed between the first adhesive medium layer 51 and the second adhesive medium layer 52.
The first adhesive medium layer 51 is applied over the entire area of the facing surface 13a of the first lens 13, and the second adhesive medium layer 52 is applied over the entire area of the facing surface 14a of the second lens 13. The facing surfaces 13a and 14a are each formed in a circular ring shape, the outer diameter of the facing surface 13a is larger than that of the facing surface 14a, and the inner diameters of the facing surfaces 13a and 14a are almost equal. Therefore, the first adhesive medium layer 51 applied to the facing surface 13a extends radially outward from the second adhesive medium layer 52 applied to the facing surface 14a. The first adhesive medium layer 51 and the second adhesive medium layer 52 have the same layer thickness, but are not limited to this and may have different layer thicknesses.
The thin plate-like inclusion 55 interposed between the first adhesive medium layer 51 and the second adhesive medium layer 52 is formed in an annular shape, and its inner and outer diameters are approximately equal to those of the opposing surface 13a. The inner and outer edges of the thin plate-like inclusion 55 are located at approximately the same radial positions as those of the inner and outer edges of the opposing surface 13a.
The upper surface (surface on the object side in the optical axis direction) of the first adhesive medium layer 51 is in close contact with the facing surface 13a, and the lower surface (surface on the image side in the optical axis direction) is in close contact with the upper surface of the thin plate-like inclusion 55. The lower surface (surface on the image side in the optical axis direction) of the second adhesive medium layer 52 is in close contact with the facing surface 14a, and the upper surface (surface on the object side in the optical axis direction) is in close contact with the lower surface of the thin plate-like inclusion 55.

As the thin plate-like inclusion 55, for example, a light-shielding plate, a heater, or a rubber sheet having light-shielding properties is used.
When the thin plate-like inclusion 55 is a light-shielding plate (e.g., a SUS plate having a thickness of 1 mm or less), a transparent or light-transmitting adhesive having a relatively high adhesive strength (higher adhesive strength than a black adhesive) can be used as the adhesive medium for forming the adhesive medium layer 50, and light-shielding properties can be reliably ensured.
As the black adhesive, for example, one having a light transmittance of 20% or less in the wavelength region of 450 nm to 650 nm is preferable. If the adhesive is made black to reduce its light transmittance, it is possible to omit the black coating process for preventing light blocking and ghosting, but there is a risk of the adhesive strength decreasing. However, in this embodiment, since a light shielding plate is interposed between the first adhesive medium layer 51 and the second adhesive medium layer 52, light blocking properties can be ensured even if the black coating process is omitted, and a transparent or translucent adhesive with a relatively high adhesive strength can be used, so that a predetermined adhesive strength can be ensured. In addition, by not performing black coating, it is possible to suppress the intrusion of moisture from between the opposing surface 13a of the first lens 13 and the surface of the thin plate-like inclusion 55.

When the thin plate-like inclusion 55 is a heater, the first lens 13 and the second lens 14 can be heated by the heater, thereby suppressing condensation in the inter-lens space S1 between the first lens 13 and the second lens 14. Even if moisture gets mixed in due to deterioration of the adhesive medium layer 50, the moisture can be heated by the heater to eliminate condensation on the lens surface.
As the heater, for example, a flat ceramic heater having a thickness of about 1 to 2 mm can be used.

When the thin plate-like inclusion 55 is a rubber sheet, the "radial tracking ability" that can follow the relative radial displacement between the lenses caused by the difference in the amount of expansion and contraction of the lenses when temperature changes due to the difference in the linear expansion coefficient between the first lens 13 and the second lens 14 is further improved. In other words, if there is a difference in the amount of expansion and contraction between the first lens 13 and the second lens 14, this difference can be mitigated by the rubber sheet, so that the "radial tracking ability" is further improved and peeling of the adhesive surface of the adhesive medium layer 50 can be prevented. The thickness of the rubber sheet is preferably about 50 to 150 μm.

In addition, in this embodiment, the adhesive medium forming the first adhesive medium layer 51 and the adhesive medium forming the second adhesive medium layer 52 may be of different types.
For example, when the first lens 13 is a glass lens and the second lens 14 is a resin lens, an adhesive medium capable of firmly bonding the glass lens (first lens 13) to the thin plate-like inclusion 55 and an adhesive medium capable of firmly bonding the resin lens (second lens 14) to the thin plate-like inclusion 55 can be easily selected, so that the first lens 13 and the second lens 14 can be bonded more firmly.

The adhesive medium used in this embodiment may be, for example, an acrylic or epoxy adhesive, or a sticky (e.g., gel-like) elastic material, and such adhesive medium is provided outside the effective diameter of the lenses 13 and 14 (opposing surfaces 13a and 14a outside the optical surface where light does not pass). These adhesive media may also be used in combination or mixed.

In addition, in this embodiment, the adhesive medium used for bonding the opposing surfaces 13a, 14a via the thin plate-like inclusion 55 has "radial followability" (flexibility sufficient to withstand radial stress applied to the adhesive interface of the lenses 13, 14 after the lenses 13, 14 expand (contract) due to temperature changes caused by the difference in linear expansion coefficient between the lenses 13, 14) that allows it to follow the relative radial displacement between the lenses 13, 14, and/or good "adhesion" (adhesion of the adhesive medium to the opposing surfaces 13a, 14a of the lenses 13, 14) that prevents the adhesive interface between the lenses 13, 14 from peeling off due to the separation of the lenses 13, 14 in the optical axis O direction caused by the increase in internal pressure of the space S1 between the lenses in a high-temperature environment, or "optical axis followability" that allows it to follow the separation displacement between the lenses 13, 14 in the optical axis O direction.

The "radial conformability" required for the adhesive medium forming the adhesive medium layer 50 can be achieved by setting the hardness of the adhesive medium within the range of Shore hardness A10 to A100 (Shore A hardness 10 to 100) or Shore hardness D10 to D90 (Shore D hardness 10 to 90). In particular, more favorable results are obtained within the range of A30 to A95 or D10 to D60. In addition to or instead of setting the hardness of the adhesive medium within such a range, such "radial conformability" can also be achieved by ensuring that the thickness (layer thickness) of the adhesive medium layer 50 is greater than or equal to a predetermined value. As a means for ensuring that the thickness of the adhesive medium layer 50 is greater than or equal to a predetermined value (ensuring the radial movement of the adhesive medium layer 50), for example, fillers are included in the adhesive medium and the maximum length of these fillers is set to 5 to 500 μm. Depending on the orientation of the filler in the adhesive medium, if the filler extends in the adhesive medium toward the optical axis O direction, the thickness of the adhesive medium layer 50 (dimension in the optical axis O direction) can be determined by the length of the extending filler.

In addition, in this embodiment, at least one of the opposing surfaces 13a, 14a of the first lens 13 and the second lens 14 may be provided with an inhibitor portion that inhibits the adhesive medium applied to the opposing surfaces 13a, 14a from flowing into the inter-lens space S1.
This preventing portion may be a recess provided in at least one part of the opposing surfaces 13a, 14a for filling with the adhesive medium, or it may be a convex portion that prevents the adhesive medium from flowing into the inter-lens space S1.

For example, as shown in FIG. 4, in this embodiment, a protrusion 60 as a suppressing portion is provided in a circular shape around the center of the annular opposing surfaces 13a, 14a on a part of each of the opposing surfaces 13a, 14a.
The convex portion 60 is provided on the inner peripheral edge of the facing surface 13a, and is provided on the facing surface 14a at a position that is a predetermined length away from the inner peripheral edge toward the outer diameter side. The height of the convex portion 60 is preferably about 5 to 500 μm. Such a convex portion 60 may be provided integrally with the first lens 13 and the second lens 14 when the first lens 13 is formed by glass molding and when the second lens 14 is formed by resin injection molding, or may be provided separately after the first lens 13 and the second lens 14 are formed.

The protrusion 60 provided on the opposing surface 13a abuts against one surface of the thin plate-like inclusion 55 facing the opposing surface 13a, and the protrusion 60 provided on the opposing surface 14a abuts against the other surface of the thin plate-like inclusion 55. Therefore, the protrusions 60, 60 can position the adhesive medium layer 50 of the thin plate-like inclusion 55 in the thickness direction, set the layer thicknesses (thicknesses) of the first adhesive medium layer 51 and the second adhesive medium layer 52, and further set the radial regions (adhesive medium filling regions) of the first adhesive medium layer 51 and the second adhesive medium layer 52 on the opposing surfaces 13a, 14a.
Furthermore, by providing the convex portion 60, it is possible to prevent the adhesive medium applied to the opposing surfaces 13a and 14a from flowing into the inter-lens space S1, and it also becomes easier to apply the adhesive medium.

A similar protrusion 60 (not shown) may be provided on the radially outer side of the opposing surfaces 13a, 14a. In this way, the layer thicknesses of the first adhesive medium layer 51 and the second adhesive medium layer 52 can be set more accurately, and the adhesive medium can be easily applied.

As shown in FIG. 5, in this embodiment, a recess 61 serving as a suppressing portion is provided in a circular shape around the center of each of the annular opposing surfaces 13a, 14a.
The recess 61 is provided on the facing surface 13a at a position away from the inner peripheral edge by a predetermined length toward the outer diameter side, and on the facing surface 14a at a position away from the inner peripheral edge by a predetermined length toward the outer diameter side, and the recesses 61, 61 correspond to each other in the optical axis direction. The depth of the recess 61 is preferably about 5 to 500 μm. Such a recess 61 may be provided integrally with the first lens 13 and the second lens 14 when the first lens 13 is formed by glass molding and when the second lens 14 is formed by resin injection molding, or may be provided separately after the first lens 13 and the second lens are formed.

The adhesive medium is applied to the opposing surfaces 13a and 14a to a predetermined thickness, but excess adhesive medium flows into the recess 61, preventing the adhesive medium from flowing into the inter-lens space S1 and making it easier to apply the adhesive medium.

6, in this embodiment, grooves 62 as restraining portions are provided in a circular shape around the center of the opposing surfaces 13a, 14a in a portion of each of the opposing surfaces 13a, 14a. The grooves 62 may be provided radially from the center of the opposing surfaces 13a, 14a. In this case, the grooves 62, 62 adjacent to each other in the circumferential direction may be equally spaced or may be unevenly spaced.
The groove 62 is provided on the facing surface 13a from a position a predetermined length away from the inner peripheral edge to the outer peripheral edge of the facing surface 13a, and on the facing surface 14a from a position a predetermined length away from the inner peripheral edge to the outer peripheral edge of the facing surface 14a. The depth of the groove 62 is preferably about 5 to 500 μm. Such a groove 62 may be provided integrally with the first lens 13 and the second lens 14 when the first lens 13 is formed by glass molding and when the second lens 14 is formed by resin injection molding, or may be provided separately after the first lens 13 and the second lens 14 are formed.

The adhesive medium is applied to the opposing surfaces 13a and 14a to a predetermined thickness, but excess adhesive medium flows into the groove 62, further preventing the adhesive medium from flowing into the inter-lens space S1 and making it easier to apply the adhesive medium.

The "adhesion" or "optical axis tracking" required for the adhesive medium forming the adhesive medium layer 50 described above can be achieved by setting the surface roughness of at least one of the opposing surfaces 13a (14a) of the first lens 13 and the second lens 14 to 0.01 μm to 200 μm in terms of root mean square roughness Rq. This is particularly beneficial when the first and second lenses 13, 14 are made of glass, for which the above-mentioned "radial tracking" does not need to be considered. This is because, in the case of glass, there is a particular concern about peeling of the adhesive interface between the lenses 13, 14 due to an increase in the internal pressure of the space S1 between the lenses in a high-temperature environment.

In addition, in this embodiment, it is further preferable that the water absorption rate of the adhesive medium is 5.0 wt% or less (JIS K6911 (boiling for 1 hour)). By setting the water absorption rate of the adhesive medium to a low level in this way, it is possible to effectively prevent water vapor from penetrating into the space between the lenses S1. In addition, in this embodiment, it is preferable that the adhesive medium is black (the light transmittance of the adhesive medium is 20% or less in the wavelength range of 450 nm to 650 nm). By making the adhesive medium black in this way and reducing its light transmittance, it is also possible to omit the inking process for blocking out light and preventing ghosting (the adhesive medium can double as ink).

In this embodiment, it is preferable that the pressure in the interlens space S1 between the first lens 13 and the second lens 14 is equal to or lower than atmospheric pressure at room temperature of 20 degrees. In this way, if the pressure in the interlens space S1 is equal to or lower than atmospheric pressure, the internal pressure of the interlens space S1 does not increase even in a high temperature environment, and this solves the problem of the adhesive interface between the lenses 13 and 14 peeling off due to the separation of the lenses 13 and 14 in the optical axis O direction caused by the increase in internal pressure. In addition, examples of methods for bonding the lens facing surfaces 13a and 14a to each other so that the pressure in the interlens space S1 is equal to or lower than atmospheric pressure include bonding the lens facing surfaces 13a and 14a to each other in a vacuum atmosphere, and bonding while suctioning and degassing the interlens space S1.

As described above, according to this embodiment, the opposing surfaces 13a, 14a of the first lens 13 and the second lens 14, which can be a path for allowing water vapor to enter the lens unit 11, are bonded to each other by the adhesive medium layer 50 so that the interlens space S1 between the first lens 13 and the second lens 14 is sealed from the outside. Therefore, even in a high humidity environment, the intrusion of water vapor into the interlens space S1, where condensation is most likely to occur, and even the intrusion of water vapor into the lens unit 11 on the image side (improving airtightness) is suppressed, the amount of water vapor in the interlens space S1 is reduced, and condensation on the lens surface, particularly on the image side surface (rear surface 13c) of the first lens 13, can be suppressed. In other words, according to such an adhesive form between the lenses 13 and 14, a highly reliable sealed state can be secured in the interlens space S1.

In addition, the adhesive medium layer 50 has a first adhesive medium layer 51 located on the first lens 13 side and a second adhesive medium layer 52 located on the second lens 14 side, and a thin plate-like inclusion 55 is interposed between the first adhesive medium layer 51 and the second adhesive medium layer 52, so that the adhesive medium forming the first adhesive medium layer 51 and the adhesive medium forming the second adhesive medium layer 52 can be of different types. Therefore, for example, when the first lens 13 is a glass lens and the second lens 14 is a resin lens, an adhesive medium capable of firmly bonding the glass lens (first lens 13) to the thin plate-like inclusion 55 and an adhesive medium capable of firmly bonding the resin lens (second lens 14) to the thin plate-like inclusion 55 can be easily selected.
Furthermore, since the thickness of the first adhesive medium layer 51 and the thickness of the second adhesive medium layer 52 can be easily set, the above-mentioned "radial followability" can be easily set and enhanced.

The present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit of the invention. For example, the shapes of the lenses, lens barrels, and the like, as well as the shapes of the protrusions and recesses, are not limited to the above-described embodiments. Furthermore, some or all of the above-described embodiments may be combined, or part of the configuration may be omitted from one of the above-described embodiments, without departing from the spirit of the invention.

REFERENCE SIGNS LIST 11 Lens unit 12 Lens barrel 13 First lens 13a Opposing surface 14 Second lens 14a Opposing surface 50 Adhesive medium layer 51 First adhesive medium layer 52 Second adhesive medium layer 55 Thin plate-like inclusion (light shielding plate, heater, rubber sheet)
60 Convex portion (restriction portion)
61 Recess (stopping portion)
62 Groove (stopping portion)
300 camera module L lens group O optical axis S inner storage space S1 space between lenses

Claims (5)

A lens unit having a lens group formed by arranging a plurality of lenses along an optical axis, and a cylindrical lens barrel having an internal storage space for incorporating, storing, and holding the lens group,
the lens group includes a first lens located closest to the object side and a second lens adjacent to the first lens on its image side, and opposing surfaces of the first lens and the second lens opposing each other in the optical axis direction are bonded together by an adhesive medium layer such that an inter-lens space between the first lens and the second lens is sealed from the outside, thereby preventing water vapor from entering the inter-lens space;
the adhesive medium layer includes a first adhesive medium layer formed by an adhesive medium applied to the opposing surface of the first lens, and a second adhesive medium layer formed by an adhesive medium applied to the opposing surface of the second lens;
A lens unit, comprising: a thin plate-like intermediate member interposed between the first adhesive medium layer and the second adhesive medium layer . The lens unit according to claim 1, characterized in that the thin plate-like inclusion is a light-shielding plate, a heater, or a rubber sheet. The lens unit according to claim 1 or 2, characterized in that the opposing surface is provided with a stopper that stops the adhesive medium applied to the opposing surface from flowing into the space between the lenses. The lens unit according to any one of claims 1 to 3, characterized in that the adhesive medium forming the first adhesive medium layer and the adhesive medium forming the second adhesive medium layer are of different types. 5. A camera module comprising: a lens unit according to claim 1 ; and an image sensor that converts light focused through the lens group of the lens unit into an electrical signal .

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