JP2024069570A - Lens unit and camera module - Google Patents

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

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.

In recent years, 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).

Figure 8 shows an example of a conventional lens unit 100. As shown in the figure, this lens unit 100 includes a cylindrical lens barrel 120 and a number of lenses arranged in the inner storage space S of the lens barrel 120, for example, a first lens 130 located closest to the object side, second to fourth lenses 140, 150, 160, and a fifth lens 170 located closest to the image side (image formation side). The multiple lenses 130, 140, 150, 160, 170 fixed and supported by the lens barrel 120 are arranged with their respective 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.

When the lens group L is assembled and housed in the inner housing space S of the lens barrel 120, the crimping portion 123 at the object side end (the upper end in FIG. 8) is crimped radially inward, so that the first lens 130, which is located closest to the object side of the lens group L, is fixed to the object side end of the lens barrel 120 by this crimping portion 123.

JP 2013-231993 A

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 concentrated stress is generated, 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. Furthermore, if such an event occurs while driving, it can also cause the vehicle to lose its safety performance.

The present invention was made in consideration of the above circumstances, and aims to provide a lens unit and camera module that can prevent damage to the lens located closest to the object side caused by a colliding object such as a flying stone.

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;
A shock absorbing layer having a Shore A hardness of 35 or less is interposed between the first lens and the second lens to absorb shock to a surface of the first lens.

The inventors have conducted extensive research into how to effectively mitigate the impact on the first lens, which is located closest to the object in the lens group, when it is struck by a flying stone or the like, and have 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 an impact absorbing layer interposed between a first glass lens and a resin plate (flat test plate) representing a second resin lens. Approximately 1,500 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.

4 and 5 show the test results when a rubber sheet is used as the shock absorbing layer. FIG. 4 is an impact distribution diagram with the horizontal axis being the hardness (shear hardness A) of the rubber sheet and the vertical axis being the thickness (mm) of the rubber sheet. FIG. 5 is a diagram showing 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 proportion of first lenses that were not broken among the multiple first lenses (glass lenses) tested under the same conditions. On the other hand, FIG. 6 and FIG. 7 show the test results when an elastic adhesive was used as the shock absorbing layer. FIG. 6 is an impact distribution diagram with the horizontal axis being the hardness (shear hardness A) of the adhesive and the vertical axis being the thickness (mm) of the adhesive layer. FIG. 7 is a diagram showing 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 proportion of first lenses that were not broken among the multiple first lenses (glass lenses) tested under the same conditions. Furthermore, when the shock absorbing layer was not provided, the first lens was damaged in approximately 50% of cases.

As can be seen from these test results, if the Shore A hardness is 32 or less in the case of a rubber sheet, or if the Shore A hardness is 30 or less in the case of an elastic adhesive, then 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. In addition, although not shown, the inventors have already confirmed through testing that similar test results can be obtained at least up to a Shore A hardness of 35.

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 test results described above. 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 test results described above. In any case, it is desirable for the shock absorbing layer to extend 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 for the shock absorbing layer to work in cooperation with a seal member (O-ring) inserted between the first lens and the lens barrel to perform a shock absorbing function.

As is clear from the test results in Figures 4 and 5, when the impact absorbing layer is a rubber sheet, it is preferable that the thickness is 0.5 mm or more. If the thickness is 0.5 mm or more, damage to the first lens can be 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 properties become, 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 performance without affecting the desired optical properties, it is preferable that the thickness of the rubber sheet is 0.5 mm or more and 1.0 mm or less.

On the other hand, as is clear from the test results in Figures 6 and 7, if the impact absorbing layer is an elastic adhesive, it is preferable that the thickness is 0.007 mm to 0.100 mm 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 before, the greater the thickness of the elastic adhesive, the greater the impact absorption properties, but if the thickness exceeds 1.0 mm, it may become difficult to maintain optical performance, as in the case of a rubber sheet, and this is not preferable.

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 be held in the lens installation interface by utilizing the surface roughness of the lenses. 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 the second lens adjacent to the first lens (the surface that interposes the adhesive between the first lens).

As described above, with the lens unit configured as above, an impact absorbing layer with 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, improving the impact resistance of the first lens against impacting objects such as flying stones and preventing damage to the first lens.

The present invention also provides a camera module equipped with a lens unit having the above-mentioned configuration. A camera module having such a configuration can also achieve the effects of the lens unit described above.

The lens unit of the present invention has an impact absorbing layer with a Shore A hardness of 35 or less interposed between the first lens and the second lens to absorb impacts on the surface of the first lens, preventing the first lens from being damaged by flying stones or other objects that collide with 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 of FIG. 1 according to an embodiment of the present invention. 13 is an enlarged view of a main portion of a lens unit having an impact absorbing layer according to a modified example. FIG. 1 is an impact distribution diagram in which the horizontal axis represents the hardness (shear hardness A) of the rubber sheet and the vertical axis represents the thickness (mm) of the rubber sheet. FIG. 5 is a table showing the distribution results (relationship between thickness and hardness of the rubber sheet) of FIG. 4 . This is an impact distribution diagram in which the horizontal axis represents the hardness of the adhesive (shear hardness A) and the vertical axis represents the thickness (mm) of the adhesive layer. FIG. 7 is a table showing the distribution results of FIG. 6 (relationship between adhesive layer thickness and hardness). FIG. 1 is a schematic cross-sectional view of a conventional lens unit.

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.

Figure 1 shows a lens unit according to one 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 equipped with 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.

The lenses 13, 14, 15, 16, and 17 are fixed to and supported by the lens barrel 12 and are arranged with their optical axes aligned, and the lenses 13, 14, 15, 16, and 17 are aligned along a single optical axis O to form a group of lenses L used for imaging. In addition, the surfaces of these lenses may be provided with anti-reflective coatings, hydrophilic coatings, water-repellent coatings, etc., as necessary.

Of the two aperture members 22a, 22b, the first aperture member 22a from the object side is disposed between the second lens 14 and the third lens 15 from the object side. The second aperture member 22b from the object side is disposed between the third lens 15 and the fourth lens 16 from the object side. The aperture 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.

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

The end (lower end in FIG. 1) of the lens barrel 12 on the image side (imaging side) 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 the lenses 13, 14, 15, 16, and 17 and the aperture members 22a and 22b that make up the lens group L within the lens barrel 12.

The outer peripheral surface 13b of the first lens 13, which is located closest to the object and which constitutes the lens group L, is provided with a reduced diameter portion 13c with a reduced diameter on the image side of the lens 13, and an O-ring 26 is provided as a sealing member on the reduced diameter portion 13c, sealing the gap between the outer peripheral surface 13b of the first lens 13 and the inner peripheral surface 12c of the lens barrel 12 at the object side end of the lens barrel 12. This prevents water, dust, and other fine particles from entering the lens barrel 12 from the object side end of the lens unit 11.

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 this 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 this 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, such as Teflon (registered trademark). 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, it is possible to change the annular body 27 to 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.

The inner diameter of the lens barrel 12 gradually decreases from the object side to the image side. Correspondingly, the outer diameters of the lenses 13, 14, 15, 16, and 17 decrease from the object side to the image 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 on-board camera.

The first lens 13, which is fixed to the object-side end of the lens barrel 12 by the crimping portion 23, has its object-side surface 13a formed as a curved convex surface that protrudes toward the object side, and the central portion (radial inner portion) 13d of its image-side surface formed as a curved concave surface recessed toward the object side. On the other hand, the second lens 14, which is adjacent to the first lens 13 on its image side, has its object-side surface central portion (radial inner portion) 14a formed as a curved concave surface recessed toward the image side. In this embodiment, an impact absorbing layer 45 with 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.

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 radially outer annular surface 13e on the image side of the first lens 13, which extends approximately perpendicular to the optical axis O, and the radially outer annular surface 14b on the object side of the second lens 14, which faces the first lens 13 and extends approximately 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.

Also, 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 12a 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 converted electrical signal is then converted into analog data or digital data, which is a component of the image data captured by the camera.

Figure 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 in 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 elastic adhesive 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 that define an adhesive reservoir 53 that holds the elastic adhesive (shock absorbing layer) 45A are formed on the annular surface 14b on the radially outer side of the object side surface of the second lens 14. 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.

As described above, according to the lens unit 11 (camera module 300) of this 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.

The present invention is not limited to the above-described embodiment, and can be modified in various ways without departing from the scope of the present invention. For example, the shapes of the lenses, lens barrel, etc., in the present invention are not limited to the above-described embodiment. The shock absorbing layer interposed between the first lens and the second lens is not limited to a rubber sheet or adhesive, and can be any material that has a shear A hardness of 35 or less and can absorb shock. 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 scope of the present invention.

REFERENCE SIGNS LIST 11 lens unit 12 lens barrel 13 first lens 14 second lens 45, 45A impact absorbing layer 50, 52 protrusion 53 adhesive reservoir 300 camera module O optical axis L lens group S inner storage space

Claims (5)

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 lens unit comprising: an impact absorbing layer having a Shore A hardness of 35 or less interposed between the first lens and the second lens for absorbing impact on a surface of the first lens. The lens unit according to claim 1, characterized in that the shock absorbing layer is a rubber sheet having a thickness of 0.5 mm or more. The lens unit of claim 1, characterized in that the impact absorbing layer is an elastic adhesive having a thickness of 0.007 mm to 0.100 mm or 0.007 mm to 0.1 mm or less and a Shore A hardness of 30 or less. The lens unit according to claim 3, characterized in that a protrusion is formed on the object side surface of the second lens adjacent to the first lens, the protrusion defining an adhesive reservoir for holding the elastic adhesive. A camera module comprising a lens unit according to any one of claims 1 to 4.

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