JP7580908B2 - 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. 16, 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. 16) 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 provided by 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 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, and especially on the back surface 100c of the first lens 100.

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, a vehicle engine).

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, or a 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 factors such as those 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 a 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 positioned 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 has a first lens located closest to the object and a second lens adjacent to the first lens on its image side, and the opposing surfaces of the first lens and the second lens, which face each other in the optical axis direction, are bonded to each other so that the inter-lens space between the first lens and the second lens is sealed from the outside.

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 to each other 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, when the opposing surfaces of a first lens and a second lens opposed to each other in the optical axis direction are bonded together using an adhesive medium, such an adhesive medium in the present invention must have "radial compliance" (flexibility sufficient to withstand radial stress applied to the lens adhesive 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 adhesive interface between the lenses from peeling off due to separation between the lenses in the optical axis direction caused by an increase in internal pressure in the space between the lenses in a high-temperature environment, or "optical axis compliance" that can follow the separation displacement between the lenses in the optical axis direction.

Examples of the adhesive medium include acrylic or epoxy adhesives, and elastic materials having adhesive properties (e.g., gel-like). Such adhesive medium is provided outside the effective diameter of the lens (a portion outside the optical surface through which light does not pass). In the above configuration, it is preferable that a seal member is provided between the first lens and the lens barrel. Such a seal member ensures sealing performance (waterproof performance) in a path that allows water vapor to enter the lens unit, and can contribute to the formation of a sealed state of the inter-lens space between the first and second lenses. In the above configuration, it is preferable that the lens barrel has a crimping portion for fixing the first lens of the lens group incorporated in the inner storage space in the optical axis direction by being crimped radially inward. Such a crimping portion generates a force in the optical axis direction that presses the first lens against the second lens, and can contribute to the adhesion of the adhesive interface between the first and second lenses, particularly the adhesion required for the above-mentioned adhesive medium. Note that instead of using rivets, a fixing cap, which is a separate member, may be used and the lens may be fixed by screwing the fixing cap in place. When using a cap, it is desirable to increase the cap screwing load so that a compressive load is applied to 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 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). It is further preferable to set the hardness 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 adhesive medium has a thickness of a predetermined value or more. As a means for ensuring that the adhesive medium has a thickness of a predetermined value or more (ensuring the adhesive medium's radial movement), for example, the adhesive medium contains fillers 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 (dimension in the optical axis direction) can be determined by the length of the extending filler.

Another method for ensuring that the thickness of the adhesive medium is greater than or equal to a predetermined value is to provide a protrusion (convex portion) with a height of 5 to 500 μm on at least one of the two opposing surfaces of the first lens and the second lens. Such a protrusion defines a filling area between the opposing surfaces of the first and second lenses for filling with the adhesive medium, and the thickness of the adhesive medium (dimension in the optical axis direction) can be structurally determined and adjusted by its height. Another method for structurally ensuring that the thickness of the adhesive medium is greater than or equal to a predetermined value is to place a sheet with a thickness of 5 to 500 μm between the opposing surfaces of the first and second lenses. Such a sheet defines a filling area between the opposing surfaces of the first and second lenses for filling with the adhesive medium, and the thickness of the sheet can be structurally determined and adjusted by its thickness. The placement of such a sheet also makes it easier to mold the lens, since it is possible to eliminate the need to process a protrusion or the like on the lens to ensure the thickness of the adhesive medium.

The "adhesion" or "optical axis tracking" required for the adhesive medium 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 aforementioned "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 due to an increase in internal pressure in the space between the lenses in a high-temperature environment.

In addition, in the above configuration, when the opposing lens surfaces are bonded together using an adhesive medium, it is preferable that a recess for filling the adhesive medium is provided in a portion of at least one of the two opposing surfaces of the opposing first lens and second lens. By providing such a recess for filling the adhesive medium, it is possible to prevent the adhesive medium from flowing out from the adhesive interface, and it is also easy to apply the adhesive medium to the adhesive interface.

In addition, in the above configuration, when the lens facing surfaces are bonded together using an adhesive medium, it is 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.

In addition, in the above configuration, when the opposing lens surfaces are bonded together using an adhesive medium, it is preferable that the adhesive medium is black (the optical 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 optical transmittance, it is possible to omit the inking process for blocking out light and preventing ghosting (the adhesive medium can also serve as ink). However, this does not prevent the use of ink and an adhesive medium in combination.

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 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 lens facing surfaces are bonded to each other using an adhesive medium, the adhesive medium may have a "radial followability" 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. Therefore, according to the present invention, even when lenses with 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 to each other so that the pressure in the interlens space is equal to or less than atmospheric pressure include bonding the lens facing surfaces to each other 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.
With this configuration, the effects of the lens unit described above can be obtained with the camera module.

According to 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 to each other 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, in particular condensation on the image-side surface (rear surface) of the first lens.

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 of FIG. 1. FIG. 2 is a schematic diagram showing a first embodiment in which opposing lens surfaces are bonded to each other using an adhesive medium. FIG. 13 is a schematic diagram showing a second embodiment in which the opposing lens surfaces are bonded to each other using an adhesive medium. FIG. 5 is a schematic diagram showing a first modified example of FIG. 4 . FIG. 5 is a schematic diagram showing a second modified example of FIG. 4 . 13A to 13D are diagrams showing four examples of projections according to the second embodiment; 5 is a plan view of a second lens showing a first example of a formation form of the protrusions in FIG. 4. FIG. 5 is a plan view of a second lens showing a second example of a formation form of the protrusions in FIG. 4. FIG. 13A to 13C are plan views of the second lens showing other examples of the formation form of the protrusions in the second embodiment. FIG. 13 is a schematic diagram showing a third embodiment in which the opposing lens surfaces are bonded to each other using an adhesive medium. 13A to 13D are diagrams showing four examples of recesses in the third embodiment. FIG. 13 is a schematic diagram showing a fourth embodiment in which the opposing lens surfaces are bonded to each other using an adhesive medium. FIG. 14 is a schematic diagram showing a first modified example of FIG. 13 . FIG. 14 is a schematic diagram showing a second modified example of FIG. 13 . 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 for a camera module such as an in-vehicle camera, and is fixedly installed on the outer surface of a vehicle, with wiring drawn 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. 16.

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 resin, 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, and two aperture members 22a and 22b. Of the two aperture members 22a and 22b, the first aperture member 22a from the object side is arranged between the second lens 14 and the third lens 15. The second aperture member 22b from the object side is arranged between the third lens 15 and the fourth lens 16. The aperture 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) for installing 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 positioned 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 inter-lens space S1 between the first lens 13 and the second lens 14 is kept sealed by bonding the opposing surfaces of the first lens 13 and the second lens 14 together (described later), and the number of lenses, the materials of the lenses and the lens barrel, etc. can be set arbitrarily depending on the application, etc. Also, in this embodiment, the two fourth and fifth lenses 16, 17 located on the image side are cemented lenses, but this does not have to be the case. Note that the surfaces of these lenses 13, 14, 15, 16, 17 are provided with anti-reflection films, hydrophilic films, water-repellent films, etc. as necessary.

In this embodiment, an O-ring 26 is inserted between the first lens 13, which is located closest to the object, and the lens barrel 12 as a seal member 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, the diameter of which is reduced at the image side portion of the lens 13, is provided on the outer circumferential surface 13d of the first lens 13, and an O-ring 26 is attached to this reduced diameter portion 13e. 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, sealing the object side end of the lens barrel 12. The seal member inserted between the first lens 13 and the lens barrel 12 is not limited to an O-ring, and may be any shape as long as it is an annular body that can seal between the first lens 13 and the lens barrel 12.

Inside the lens barrel 12, a cylindrical inner wall 12b is provided on the object side, and a groove 18 is formed between the inner wall 12b and the outer wall 12c. A ring-shaped body 27 is provided in the groove 18, and an O-ring 26 is in close contact with the ring-shaped body 27. The reason for forming the groove 18 between the inner wall 12b and the outer wall 12a is to prevent a large sink mark from occurring when molding and cooling the resin lens barrel 12, which would cause a loss of dimensional accuracy, since the wall thickness would be thick if the inner wall 12b and the outer wall 12a were integrated without a groove. The ring-shaped body 27 is made of a relatively soft elastic material, such as Teflon. 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 a different height depending on the size of the O-ring 26, ensuring 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 (upper end in FIG. 1) is thermally crimped radially inward, thereby fixing the first lens 13, which is 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.

The end of the lens barrel 12 on the image side (the lower end in FIG. 1) is provided with an inner flange portion 24 having an opening with a smaller diameter than the fifth lens 17. The inner flange portion 24 and the crimped portion 23 hold and fix the 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 gradually decreases 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. In addition, an outer flange portion 25 is provided on the outer peripheral surface of the lens barrel 12 in the shape of a brim, which is used when installing the lens barrel 12 in an in-vehicle camera.

FIG. 2 is a schematic cross-sectional view of a camera module 300 of this embodiment having the lens unit 11 of FIG. 1. As shown in the figure, the camera module 300 is configured to include the lens unit 11 to which the filter 100 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, the first lens 13 located closest to the object 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 to each other so that the inter-lens space S1 between the first lens 13 and the second lens 14 is sealed from the outside.

In particular, in this embodiment, the opposing surfaces 13a, 14a are bonded to each other using the adhesive medium 40 (see FIGS. 1 and 2), but the opposing surfaces 13a, 14a may be bonded to each other using other adhesive forms.
Here, examples of the adhesive medium 40 used in this embodiment include acrylic or epoxy adhesives, and elastic materials having tackiness (e.g., gel-like), and such adhesive medium 40 is provided outside the effective diameters of the lenses 13 and 14 (outside the optical surfaces where light does not pass). The state in which the adhesive medium 40 is thus disposed between the opposing surfaces 13a and 14a is shown in a somewhat exaggerated schematic view particularly in FIG.

In addition, in this embodiment, the adhesive medium 40 used to bond the opposing surfaces 13a and 14a has "radial followability" (flexibility sufficient to withstand radial stress applied to the adhesive interface of the lenses 13 and 14 after the lenses 13 and 14 expand (contract) due to temperature changes caused by the difference in the linear expansion coefficients of the lenses 13 and 14) that allows it to follow the relative radial displacement between the lenses 13 and 14, and/or good "adhesion" (adhesion of the adhesive medium 40 to the opposing surfaces 13a and 14a of the lenses 13 and 14) that prevents the adhesive interface between the lenses 13 and 14 from 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 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 and 14 in the optical axis O direction.

The "radial conformability" required for the adhesive medium 40 can be achieved by setting the hardness of the adhesive medium 40 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 adhesive medium has a thickness of a predetermined value or more. As a means for ensuring that the adhesive medium 40 has a thickness of a predetermined value or more (ensuring the radial movement of the adhesive medium 40), for example, fillers are included in the adhesive medium 40 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 40 toward the optical axis O direction, the thickness of the adhesive medium 40 (dimension in the optical axis O direction) can be determined by the length of the extending filler.

Another method for ensuring that the adhesive medium 40 is thicker than a predetermined thickness is to provide a protrusion (convex portion) with a height of 5 to 500 μm on at least one of the two opposing surfaces 13a, 14a of the first lens 13 and the second lens 14 that face each other. Examples of such a method are shown in Figures 4 to 6.

In Figure 4, a protrusion 43 is provided on the radially outer side (outermost side) of the opposing surface 14a of the second lens 14 with a height of 5 to 500 μm, and this protrusion 43 may be annular (zonal) as shown in Figure 8 (annular protrusion 43A), or may be a plurality of columnar protrusions 43B with a circular cross section arranged at a predetermined angular interval from each other along the circumferential direction as shown in Figure 9 (in the figure, four columnar protrusions are spaced at angular intervals of 90° along the circumferential direction). Such protrusions 43 (43A, 43B) abut against the opposing surface 13a of the first lens 13, and define a filling area for filling the adhesive medium 40 between the opposing surfaces 13a, 14a of the first and second lenses 13, 14 (in the case of the annular protrusion 43A, radially inward from the annular protrusion 43A (see FIG. 8), and in the case of the columnar protrusion 43B, between the columnar protrusions 43B and radially inward from the columnar protrusions 43B (see FIG. 9)). The thickness (dimension in the optical axis O direction) of the adhesive medium 40 can be structurally defined and adjusted by its height. When filling the adhesive medium 40, the annular protrusion 43A shown in FIG. 8 makes it easy to control the filling flow of the adhesive medium 40, and can also prevent the adhesive medium 40 from flowing out of the opposing surface 14a. In contrast, the columnar protrusion 43B shown in FIG. 9 can secure a wide adhesive area, thereby increasing the adhesive force.

In FIG. 5, a protrusion 43 is provided with a height of 5 to 500 μm near the center of the radial direction of the facing surface 14a of the second lens 14. In this case, the protrusion 43 may be an annular protrusion 43A as shown in FIG. 8, or may be a plurality of columnar protrusions 43B as shown in FIG. 9. Such protrusions 43 (43A, 43B) abut against the facing surface 13a of the first lens 13 to define a filling area for filling the adhesive medium 40 between the facing surfaces 13a, 14a of the first and second lenses 13, 14 (both the radial inner and outer sides of the annular protrusion 43A in the case of the annular protrusion 43A, and both the radial inner and outer sides of the columnar protrusions 43B in the case of the columnar protrusions 43B), and the thickness of the adhesive medium 40 (dimension in the optical axis O direction) can be structurally defined and adjusted depending on the height.

In FIG. 6, a protrusion 43 is provided with a height of 5 to 500 μm on the radially inner side of the opposing surface 14a of the second lens 14 (for example, with an annular region 49 (region within the effective diameter of the lens) remaining further inward; in FIGS. 4 and 5, the annular region 49 is secured as a region that is not filled (applied) with the adhesive medium 40). In this case, too, the protrusion 43 may be an annular protrusion 43A as shown in FIG. 8, or may be a plurality of columnar protrusions 43B as shown in FIG. 9. Such protrusions 43 (43A, 43B) abut against the opposing surface 13a of the first lens 13 and define a filling area for filling the adhesive medium 40 between the opposing surfaces 13a, 14a of the first and second lenses 13, 14 (in the case of the annular protrusion 43A, the radial outside of the annular protrusion 43A, and in the case of the columnar protrusion 43B, between the columnar protrusions 43B and the radial outside of the columnar protrusions 43B), and the thickness (dimension in the direction of the optical axis O) of the adhesive medium 40 can be structurally determined and adjusted by its height.
4 to 6, the annular protrusion 43 is provided at only one location, but the number of locations can be set arbitrarily. For example, the annular protrusions 43 may be provided at two locations, one on the outer side and one on the inner side of the facing surface 14a. Similarly, the number of columnar protrusions 43B shown in FIG. 9 is not limited to four, and the purpose of ensuring the thickness of the adhesive medium 40 can be achieved by providing three or more.

The cross-sectional shape (cross-section cut along a plane extending in the radial direction) of the protrusions 43 (43A, 43B) may be a square as shown in FIG. 7(a) (or other rectangular shape such as a rectangle), a triangle as shown in FIG. 7(b), a trapezoid as shown in FIG. 7(c), or a semicircle as shown in FIG. 7(d). Of course, it is not limited to these shapes, and any shape can be selected as appropriate.

The protrusions provided on the opposing surface 14a of the second lens 14 may be radially extending protrusions 43C extending along the radial direction, as shown in FIG. 10. In this case, it is preferable to adopt the cross-sectional shape of the protrusions 43C as shown in FIG. 7. In particular, in FIG. 10, the radially extending protrusions 43C are provided radially (four radially extending protrusions 43C are provided at 90° angular intervals from each other in the circumferential direction). Such radially extending protrusions 43C define a filling area for filling the adhesive medium 40 between the radially extending protrusions 43C, and by dividing the adhesive surface (adhesive layer), it is possible to prevent the adhesive layer from peeling off overall. In other words, by dividing the adhesive layer, even if a part of the adhesive layer peels off, it is possible to suppress such peeling from spreading over the entire adhesive surface. Note that, although four radially extending protrusions 43C are set in FIG. 10, this is not limited thereto, and the desired purpose can be achieved by setting three or more.

In the examples of Figs. 4 to 10, the protrusions 43 (43A, 43B, 43C) are provided only on the facing surface 14a of the second lens 14, but the protrusions 43 (43A, 43B, 43C) may be provided on the facing surface 13a of the first lens 13, or the protrusions 43 (43A, 43B, 43C) may be provided on both of the two facing surfaces 13a, 14a of the first lens 13 and the second lens 14. Also, instead of the protrusions, a recess for filling the adhesive medium 40 may be provided on at least one part of the two facing surfaces 13a, 14a of the first lens 13 and the second lens 14 that face each other. For example, in Fig. 11, an annular recess 47 is provided near the center in the radial direction of the facing surface 14a of the second lens 14. Providing such a recess 47 for filling the adhesive medium can prevent the adhesive medium 40 from flowing out from the adhesive interface, and also makes it easier to apply the adhesive medium 40 to the adhesive interface. The cross-sectional shape of the recess 47 (cross-section cut along a plane extending in the radial direction) may be a rectangle as shown in FIG. 12(a), a triangle as shown in FIG. 12(b), a trapezoid as shown in FIG. 12(c), or a semicircle as shown in FIG. 12(d). Of course, the shape is not limited to these shapes, and any shape can be appropriately selected. In addition, the width of the recess is preferably 10 to 95%, more preferably 30 to 90%, of the area where the lenses 13 and 14 face each other in the radial direction in order to ensure both the lens contact area and the adhesive area.

Another method for structurally ensuring that the thickness of the adhesive medium 40 is greater than or equal to a predetermined thickness is to place a sheet with a thickness of 5 to 500 μm between the opposing surfaces 13a, 14a of the first and second lenses 13, 14. Examples of such a method are shown in Figures 13 to 15, respectively.

In FIG. 13, an annular sheet 52 is disposed with a thickness of 5 to 500 μm on the radially outer side between the opposing surfaces 13a, 14a. Such a sheet 52 is interposed between the opposing surfaces 13a, 14a to define a filling area for filling the adhesive medium 40 radially inward of the sheet 52 between the opposing surfaces 13a, 14a, and the thickness of the sheet 52 can be structurally determined and adjusted to the thickness of the adhesive medium 40 (dimension in the optical axis O direction). In addition, such an arrangement of the sheet 52 can eliminate the need to machine and provide protrusions, etc. on the lenses 13, 14 as described above to ensure the adhesive medium thickness, and can therefore facilitate the molding of the lenses 13, 14.

In FIG. 14, an annular sheet 52 is disposed with a thickness of 5 to 500 μm near the radial center between the opposing surfaces 13a, 14a. Such a sheet 52 is interposed between the opposing surfaces 13a, 14a to define a filling area for filling the adhesive medium 40 on both the radial inside and outside of the sheet 52 between the opposing surfaces 13a, 14a, and the thickness of the sheet 52 can be structurally determined and adjusted to define the thickness of the adhesive medium 40 (dimension in the direction of the optical axis O).

15, an annular sheet 52 is disposed with a thickness of 5 to 500 μm on the radially inner side between the opposing surfaces 13 a, 14 a. Such a sheet 52 is interposed between the opposing surfaces 13 a, 14 a to define a filling area for filling the adhesive medium 40 on the radially outer side of the sheet 52 between the opposing surfaces 13 a, 14 a, and the thickness of the sheet 52 (the dimension in the optical axis O direction) can be structurally defined and adjusted by the thickness of the sheet 52.
13 to 15, the annular sheet 52 is provided at only one location, but the location can be set arbitrarily. For example, the annular sheet 52 may be provided at two locations, one on the outer side and one on the inner side of the facing surface 14a. The annular sheet 52 may be a radial sheet extending along the radial direction, as shown in FIG.

The "adhesion" or "optical axis tracking" required for the adhesive medium 40 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 aforementioned "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 preferable that the water absorption rate of the adhesive medium 40 is 5.0 wt% or less (JIS K6911 (boiling for 1 hour)). By setting the water absorption rate of the adhesive medium 40 to a low value in this way, it is possible to effectively suppress the intrusion of water vapor into the space between the lenses S1. In addition, in this embodiment, it is preferable that the adhesive medium 40 is black (the light transmittance of the adhesive medium 40 is 20% or less in the wavelength range of 450 nm to 650 nm). By making the adhesive medium 40 black and suppressing its light transmittance in this way, it is possible to omit the ink painting process for preventing light blocking and ghosting (the adhesive medium 40 can also serve as ink). Furthermore, it is preferable that the sheet 52 is made of a material with a light transmittance of 20% or less in the range of 450 to 650 nm and a one-sided reflectance of 10% or less. This makes it possible to suppress the occurrence of ghosts and flares caused by stray light. For example, a light-shielding material made of resin, such as that used as an aperture member, or a light-shielding material made of a thin metal plate that has been blackened can be used. In this embodiment, the pressure in the interlens space S1 between the first lens 13 and the second lens 14 is preferably 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 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 can be eliminated. In addition, as a method of 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, for example, bonding the lens facing surfaces 13a and 14a to each other in a vacuum atmosphere, or bonding while suctioning and degassing the interlens space S1 can be mentioned.

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 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 further into the lens unit 11 on the image side are suppressed (improving airtightness), reducing the amount of water vapor in the interlens space S1 and suppressing condensation on the lens surface, particularly on the image side surface (rear surface 13c) of the first lens 13. In other words, according to this type of bonding between the lenses 13 and 14, a highly reliable sealed state can be secured in the interlens space S1.

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, the above-described embodiments may be combined in part or in whole, 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 40 Adhesive medium 43, 43A, 43B, 43C Protrusion 47 Recess 52 Sheet 300 Camera module L Lens group O Optical axis S Inner storage space S1 Space between lenses

Claims (12)

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 inner accommodation space for accommodating 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;
the second lens has a smaller diameter than the first lens,
A lens unit characterized in that, in the path of water vapor intrusion that passes between the lens barrel and the lens and reaches the inter-lens space between the first lens and the second lens, the opposing surfaces of the first lens and the second lens that face each other in the optical axis direction are bonded to each other so that the inter-lens space is sealed from the outside. The lens unit according to claim 1, characterized in that the adhesion is performed using an adhesive medium, and the hardness of the adhesive medium is within the range of A10 to A100 or within the range of D10 to D90 in Shore hardness. The lens unit according to claim 1, characterized in that the adhesion is performed using an adhesive medium, the adhesive medium contains a filler to ensure the thickness of the layer, and the maximum length of the filler is 5 to 500 μm. The lens unit according to claim 1, characterized in that the bonding is performed using an adhesive medium, and at least one of the two opposing surfaces of the first lens and the second lens facing each other is provided with a protrusion having a height of 5 to 500 μm on a part thereof to ensure the thickness of the layer of the adhesive medium. The lens unit according to claim 1, characterized in that the bonding is performed using an adhesive medium, and a sheet having a thickness of 5 to 500 μm is placed between the opposing surfaces of the first lens and the second lens to ensure the thickness of the layer of the adhesive medium. The lens unit according to claim 1, characterized in that the bonding is performed using an adhesive medium, and at least one of the two opposing surfaces of the first lens and the second lens facing each other is provided with a recess in a part thereof for filling the adhesive medium. The lens unit according to any one of claims 1 to 6, characterized in that at least one of the first lens and the second lens has a surface roughness of 0.01 μm to 200 μm in terms of root mean square roughness Rq of the opposing surface. The lens unit according to any one of claims 1 to 7, characterized in that the adhesion is performed using an adhesive medium, and the water absorption rate of the adhesive medium is 5.0 wt% or less (JIS K6911 (boiling for 1 hour)). The lens unit according to any one of claims 1 to 8, characterized in that the adhesion is performed using an adhesive medium, which is black and has a light transmittance of 20% or less in the wavelength range of 450 nm to 650 nm. The lens unit according to any one of claims 1 to 9, characterized in that one of the first lens and the second lens is made of glass and the other is made of resin, or the first lens and the second lens are both made of resin and have a difference in linear expansion coefficient between them of 40 x 10 ^-6 /K (m) or more. The lens unit according to any one of claims 1 to 10, characterized in that the pressure in the interlens space between the first lens and the second lens is equal to or lower than atmospheric pressure. A camera module comprising a lens unit according to any one of claims 1 to 11.

Images