Lens units and camera modules

Abstract

To provide a lens unit and a camera module, with which it is possible to prevent the lens positioned on the most object side from being broken by a colliding object such as a stepping stone.SOLUTION: A lens unit 11 of the present invention comprises a first lens 13 positioned on the most object side and a second lens 14 adjacent to the first lens 13 on its image side. Between the first lens 13 and the second lens 14 is interposed an impact absorption layer 45 of Shore A hardness 35 or lower for absorbing an impact shock to the surface of the first lens 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a lens unit and a camera module that can constitute an on-board camera mounted on a vehicle such as an automobile. [Background technology]

[0002] In recent years, automobiles have been equipped with on-board cameras to support parking and prevent collisions through image recognition, and attempts are also being made to apply them to autonomous driving. In addition, camera modules such as such on-board cameras generally include a lens unit having a lens group consisting of multiple lenses arranged along an optical axis, a lens barrel that houses and holds the lens group, and an aperture member arranged between at least one of the lenses in the lens group (for example, see Patent Document 1).

[0003] 8 shows an example of a conventional lens unit 100. As shown in the figure, the lens unit 100 includes a cylindrical lens barrel 120 and a plurality of lenses arranged in an inner storage space S of the lens barrel 120, for example, a first lens 130 positioned closest to the object side, second to fourth lenses 140, 150, 160, and a fifth lens 170 positioned closest to the image side (image formation side). The lenses 130, 140, 150, 160, 170 fixed to and supported by the lens barrel 120 are arranged with their optical axes aligned, and are arranged along a single optical axis O to form a group of lenses L used for imaging by a package sensor (imaging element; not shown) via a filter 250.

[0004] With lens group L assembled and housed within inner housing space S of barrel 120, crimping portion 123 at the object side end (upper end in FIG. 8) is crimped radially inward, thereby fixing first lens 130, which is positioned closest to the object side of lens group L, to the object side end of barrel 120 by crimping portion 123. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-231993 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when such a lens unit 100 constitutes an in-vehicle camera mounted on a vehicle, a foreign object such as a flying stone may collide with the surface (object side surface) of the first lens 130 while the vehicle is traveling. In this way, when an instantaneous impact is applied from the outside due to a flying stone or the like colliding with the first lens 130, the stress at the time of the collision is not alleviated and a concentrated stress occurs, causing the first lens to break. Such breakage not only significantly impairs the appearance, but also significantly impairs the viewing and sensing functions of the lens unit 100, deteriorating the optical characteristics. In addition, if such an event occurs while traveling, the safety performance of the vehicle will be lost.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a lens unit and a camera module that can prevent damage to the lens located closest to the object side by a colliding object such as a flying stone. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a lens unit having a lens group formed by arranging a plurality of lenses along the optical axes of the lenses, 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; The present invention is characterized in that an impact absorbing layer having a Shore A hardness of 35 or less is interposed between the first lens and the second lens to absorb impact on the surface of the first lens.

[0009] The inventors conducted extensive research into how to effectively mitigate an impact when a first lens that constitutes a lens group and is located closest to the object receives an impact from a flying stone or the like, and discovered that by interposing an impact absorbing layer having a Shore A hardness of 35 or less between the first lens and the second lens adjacent to the first lens on the image side, damage to the first lens can be avoided with a probability of 50% or more. Specifically, a stone impact test was carried out using a device conforming to DIN EN ISO20567-1, with the impact absorbing layer interposed between a first glass lens and a resin plate (flat test plate) which resembled a second resin lens. Approximately 1500 pieces (500 g) of cast iron grids (diameter 3.5 mm to 5.0 mm) weighing approximately 0.3 g were radially injected toward the first lens (the object side surface of the lens) from a point 50 to 60 cm away from the first lens with an injection pressure of 0.125 MPa for 10 seconds, and the damage state of the first lens was confirmed while changing the thickness and hardness of the impact absorbing layer. The results are shown in Figures 4 to 7.

[0010] 4 and 5 show the test results when a rubber sheet is used as the shock absorbing layer. FIG. 4 shows an impact distribution diagram with the horizontal axis being the hardness of the rubber sheet (shear hardness A) and the vertical axis being the thickness (mm) of the rubber sheet. FIG. 5 shows the distribution results of FIG. 4 (relationship between the thickness and hardness of the rubber sheet) in a table. The percentages (%) in FIG. 4 and FIG. 5 indicate the ratio of the first lenses that were not broken among the multiple first lenses (glass lenses) tested under the same conditions. Meanwhile, FIG. 6 and FIG. 7 show the test results when an elastic adhesive is used as the shock absorbing layer. FIG. 6 shows an impact distribution diagram with the horizontal axis being the hardness of the adhesive (shear hardness A) and the vertical axis being the thickness (mm) of the adhesive layer. FIG. 7 shows the distribution results of FIG. 6 (relationship between the layer thickness and hardness of the adhesive) in a table. The percentages (%) in FIG. 6 and FIG. 7 indicate the ratio of the first lenses that were not broken among the multiple first lenses (glass lenses) tested under the same conditions. When the impact absorbing layer was not provided, the first lens was damaged in approximately 50% of cases.

[0011] As can be seen from these test results, by adjusting the thickness, damage to the first lens can be avoided (the lens will not be damaged) with a probability of 50% or more if the rubber sheet has a Shore A hardness of 32 or less, and if the elastic adhesive has a Shore A hardness of 30 or less. In addition, although not shown, the inventors have already confirmed through tests that similar test results can be obtained at least up to a Shore A hardness of 35.

[0012] As the rubber sheet, it is preferable to use acrylic rubber or silicone rubber. By using these rubbers, it is possible to obtain results similar to the above-mentioned test results. As the elastic adhesive, it is preferable to use an adhesive mainly composed of modified acrylate. By using these adhesives, it is possible to obtain results similar to the above-mentioned test results. In any case, it is desirable that the shock absorbing layer extends at least over the entire contact surface where the first lens and the second lens come into contact, preferably over the entire image side surface of the first lens, and more preferably over the entire outer diameter dimension of the first lens, and it is even more desirable that the shock absorbing layer cooperates with a seal member (O-ring) interposed between the first lens and the lens barrel to perform a shock absorbing function.

[0013] In addition, as is clear from the test results of Figs. 4 and 5, when the impact absorbing layer is a rubber sheet, the thickness is preferably 0.5 mm or more. If the thickness is 0.5 mm or more, damage to the first lens can be reliably avoided with a probability of 50% or more when the Shore A hardness is 35 or less. The thicker the rubber sheet is, the greater the impact absorption property becomes, but if the thickness exceeds 1.0 mm, it becomes difficult to maintain the desired optical performance while achieving miniaturization. Therefore, in order to obtain good impact absorption ability without affecting the desired optical properties, the thickness of the rubber sheet is preferably 0.5 mm or more and 1.0 mm or less.

[0014] On the other hand, as is clear from the test results in Fig. 6 and Fig. 7, when the impact absorbing layer is an elastic adhesive, it is preferable that the thickness is 0.007mm to 0.100mm and the Shore A hardness is 30 or less. If the thickness and hardness are within this range, damage to the first lens can be avoided with a probability of 50% or more. In this case, as in the previous case, the thicker the elastic adhesive is, the greater the impact absorption properties are, but if the thickness exceeds 1.0mm, it may become difficult to maintain optical performance as in the case of a rubber sheet, which is not preferable.

[0015] In order to prevent the elastic adhesive from spilling out between the lenses and flowing into the lens group, it is preferable that the elastic adhesive is held in the lens installation interface by utilizing the surface roughness of the lenses, etc. In order to provide such an adhesive holding function, for example, a protrusion that defines an adhesive reservoir that holds the elastic adhesive may be formed on the object side surface of a second lens adjacent to the first lens (the surface that interposes the adhesive between the first lens and the second lens).

[0016] As described above, according to the lens unit configured as above, an impact absorbing layer having a Shore A hardness of 35 or less is interposed between the first lens and the second lens to absorb impacts on the surface of the first lens, thereby improving the impact resistance of the first lens against flying stones and other colliding objects and preventing damage to the first lens.

[0017] The present invention also provides a camera module including the lens unit having the above-mentioned configuration. A camera module having such a configuration can also obtain the effects of the lens unit described above. Effect of the Invention

[0018] According to the lens unit of the present invention, an impact absorbing layer having a Shore A hardness of 35 or less is interposed between the first lens and the second lens to absorb impacts on the surface of the first lens, thereby preventing the first lens from being damaged by a colliding object such as a flying stone. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view of a lens unit according to an embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view of a camera module having the lens unit of FIG. 1 according to an embodiment of the present invention. [Diagram 3] 13 is an enlarged view of a main portion of a lens unit having an impact absorbing layer according to a modified example. FIG. [Figure 4] This is an impact distribution diagram in which the horizontal axis is the hardness of the rubber sheet (shear hardness A) and the vertical axis is the thickness of the rubber sheet (mm). [Diagram 5] FIG. 5 is a table showing the distribution results of FIG. 4 (the relationship between the thickness and hardness of the rubber sheet). [Figure 6] This is an impact distribution diagram in which the horizontal axis is the hardness of the adhesive (shear hardness A) and the vertical axis is the thickness of the adhesive layer (mm). [Figure 7] FIG. 7 is a table showing the distribution results of FIG. 6 (relationship between adhesive layer thickness and hardness). [Figure 8] FIG. 1 is a schematic cross-sectional view of a conventional lens unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The lens unit of the present embodiment described below is particularly for a camera module such as an in-vehicle camera, 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. Also, hatching of the lenses is omitted in Figures 1 to 3 and 8.

[0021] 1 shows a lens unit 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, 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. An in-vehicle camera including this lens unit 11 includes the lens unit 11, a board having an image sensor (not shown), and an installation member (not shown) for installing the board on a vehicle such as an automobile.

[0022] The multiple lenses 13, 14, 15, 16, and 17 fixed to and supported by the lens barrel 12 are 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. Note that the surfaces of these lenses may be provided with an anti-reflection film, a hydrophilic film, a water-repellent film, or the like, as necessary.

[0023] Of the two diaphragm members 22a, 22b, the first diaphragm member 22a from the object side is disposed between the second lens 14 and the third lens 15 from the object side. The second diaphragm member 22b from the object side is disposed between the third lens 15 and the fourth lens 16 from the object side. The diaphragm members 22a, 22b are either "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.

[0024] At the object side end of barrel 12 (the upper end in FIG. 1), a crimped portion 23 is provided by crimping the end radially inward, and lens 13 located closest to the object side of lens group L is fixed to the object side end of barrel 12 by this crimped portion 23. Note that in this embodiment, barrel 12 is made of resin, lens 13 located closest to the object side is a glass lens, and the other lenses are resin lenses, but this is not limited to this.

[0025] Further, an inner flange portion 24 having an opening with a diameter smaller than that of fifth lens 17 is provided at the end (lower end in FIG. 1) of the image side (imaging side) of lens barrel 12. Multiple lenses 13, 14, 15, 16, and 17 and diaphragm members 22a and 22b constituting lens group L within lens barrel 12 are held by this inner flange portion 24 and crimped portion 23.

[0026] On outer peripheral surface 13b of first lens 13 located closest to the object side and constituting lens group L, reduced diameter portion 13c having a reduced diameter is provided on the image side portion of lens 13, and O-ring 26 as a seal member is provided on reduced diameter portion 13c, so that the gap between outer peripheral surface 13b of first lens 13 and inner peripheral surface 12c of lens barrel 12 is sealed at the object side end of lens barrel 12. This prevents fine particles such as water and dust from entering lens barrel 12 from the object side end of lens unit 11.

[0027] In addition, a cylindrical inner wall 12b is provided on the object side inside the lens barrel 12, and a groove 18 is formed between the inner wall 12b and the outer wall 12c. An annular body 27 is provided in the groove 18, and an O-ring 26 is in close contact with the annular body 27. The reason for forming the groove 18 between the inner wall 12b and the outer wall 12a is to suppress the occurrence of large sink marks and the deviation of dimensional accuracy when molding and cooling the resin lens barrel 12, since the wall thickness becomes thick if the inner wall 12b and the outer wall 12a are integrated without a groove. The annular body 27 is made of a relatively soft elastic material, and Teflon (registered trademark) is used, for example. The annular body 27 has the function of supporting the O-ring 26 in the optical axis direction. Since the annular body 27 is a separate member from the lens barrel 12, the annular body 27 can be changed to a different height depending on the size of the O-ring 26, and the O-ring 26 is guaranteed to seal with an appropriate elastic force.

[0028] The inner diameter of the lens barrel 12 becomes smaller in stages from the object side to the image side. Correspondingly, the outer diameter of the lenses 13, 14, 15, 16, and 17 becomes smaller from the object side to the image side. Basically, the outer diameter of each of the lenses 13, 14, 15, 16, and 17 and the inner diameter of each of the portions of the lens barrel 12 where the lenses 13, 14, 15, 16, and 17 are supported are approximately equal. 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 a vehicle-mounted camera.

[0029] The first lens 13, which is fixed to the object-side end of the lens barrel 12 by the crimping portion 23, has an object-side surface 13a formed as a curved convex surface protruding toward the object side, and a central portion (radial inner portion) 13d of the image-side surface formed as a curved concave surface recessed toward the object side. On the other hand, the second lens 14 adjacent to the first lens 13 on its image side has a central portion (radial inner portion) 14a of its object-side surface formed as a curved concave surface recessed toward the image side. In this embodiment, an impact absorbing layer 45 having a Shore A hardness of 35 or less is interposed between the first lens 13 and the second lens 14 to absorb impacts on the surface (object-side surface 13a) of the first lens 13.

[0030] In this embodiment, the shock absorbing layer 45 is formed of a rubber sheet made of acrylic rubber or silicone rubber and has a thickness of 0.5 mm or more, and is interposed between the image-side radially outer annular surface 13e of the first lens 13 extending substantially perpendicular to the optical axis O and the object-side radially outer annular surface 14b of the second lens 14 extending substantially perpendicular to the optical axis O. The shock absorbing layer 45 extends at least over the entire contact area between the first lens 13 and the second lens 14, preferably over the entire image-side annular surface 13e of the first lens 13, and particularly over the entire outer diameter of the first lens 13 in this embodiment.

[0031] Moreover, 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.

[0032] 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 seal member 303 and a package sensor (imaging element) 304.

[0033] Upper case 301 is a member that exposes the object side end of lens unit 11 and covers other portions. Mount 302 is disposed inside upper case 301, and has female threads 302a that screw into male threads 11a of lens unit 11. Sealing member 303 is a member that is interposed between the inner surface of upper case 301 and outer peripheral surface 12a of barrel 12 of lens unit 11, and is a member that maintains airtightness inside upper case 301.

[0034] Package sensor 304 is disposed inside mount 302, and is disposed at a position where it receives an image of an object formed by lens unit 11. Package sensor 304 also includes a CCD, CMOS, or the like, and converts the light that is collected and reaches it through lens unit 11 into an electrical signal. The converted electrical signal is then converted into analog data or digital data, which is a component of image data captured by the camera.

[0035] FIG. 3 shows a modified example of the shock absorbing layer interposed between the first lens 13 and the second lens 14. The shock absorbing layer 45A according to this modified example is formed as a layer of elastic adhesive, and has a thickness of 0.007 mm to 0.100 mm and a Shore A hardness of 30 or less. The shock absorbing layer 45A made of an elastic adhesive layer is preferably held on the annular surfaces 13e and 14b of the lenses 13 and 14 so as to prevent the shock absorbing layer 45A from protruding from between the lenses 13 and 14 and flowing into the lens group L in particular. As such an adhesive holding function, it is possible to hold the adhesive in the installation interface between the lenses 13 and 14 by utilizing the surface roughness of the lenses 13 and 14, but in this embodiment, as an adhesive holding function, protrusions 50 and 52 are formed on the annular surface 14b on the radially outer side of the object side surface of the second lens 14 to define an adhesive reservoir 53 that holds the elastic adhesive (shock absorbing layer) 45A. Specifically, in this embodiment, an annular adhesive reservoir 53 is defined by a first annular protrusion 50 formed on the radially outer edge of the annular surface 14b and a second annular protrusion 52 formed on the radially inner edge of the annular surface 14b.

[0036] As described above, according to the lens unit 11 (camera module 300) of the present embodiment, an impact absorbing layer 45 (45A) having a Shore A hardness of 35 or less is interposed between the first lens 13 and the second lens 14 to absorb impacts on the surface of the first lens 13. This improves the impact resistance of the first lens 13 against impacting objects such as flying stones, and prevents damage to the first lens 13.

[0037] The present invention is not limited to the above-mentioned embodiment, and can be modified in various ways without departing from the gist of the present invention. For example, the shapes of the lens, lens barrel, etc. are not limited to the above-mentioned embodiment. The shock absorbing layer interposed between the first lens and the second lens is not limited to a rubber sheet or adhesive, and may be any material that has a shear A hardness of 35 or less and can absorb shock. In addition, the above-mentioned embodiments may be combined in part or in whole, or a part of the configuration may be omitted from one of the above-mentioned embodiments, without departing from the gist of the present invention. [Explanation of symbols]

[0038] 11 Lens unit 12 Telescope tube 13 The First Lens 14 The Second Lens 45,45A Shock absorbing layer 50,52 protrusion 53 Adhesive Pool 300 Camera Module O optical axis L lens group S Inner storage space

Claims

1. A lens unit having a lens group formed by arranging a plurality of lenses along the optical axis of the lenses, 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; a seal member is provided on an outer circumferential surface of the first lens; an annular body that supports the seal member in the optical axis direction is provided inside the lens barrel; an impact absorbing layer having a Shore A hardness of 35 or less is interposed between the first lens and the second lens to absorb impact caused by a foreign object colliding with a surface of the first lens; an outer circumferential edge of the impact absorbing layer abuts against an inner circumferential surface of the lens barrel; The impact absorbing layer is a rubber sheet having a thickness of 0.5 mm or more and 1.0 mm or less, a lens unit, characterized in that an outer periphery of the rubber sheet is sandwiched between the sealing member and the annular body.

2. A camera module comprising the lens unit according to claim 1.

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