Lens unit, camera module, in-vehicle system and vehicle

Abstract

To provide a lens unit, a camera module, an onboard system and a vehicle with which it is possible to reduce the deformation of a lens in the optical axis direction due to a difference in coefficient of linear expansion between a barrel and the lens.SOLUTION: In this lens unit 11, at least one lens that constitutes a lens group L is a resin lens 14, 15, 17 formed from resin, and the resin lens is larger in the coefficient of linear expansion than that of a barrel 12 and is built into an inside accommodation space S by pressure. A buffer layer 30 that absorbs and mitigates compressive stress acting upon the resin lens toward the radial inside is interposed between the radially outside circumferential surface 14a, 15a, 17a of the resin lens 14, 15, 17 and the inside surface 12a of the barrel 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention particularly relates to a lens unit constituting an on-board camera mounted on a vehicle such as an automobile, a camera module, an on-board system, and a vehicle equipped with the on-board system. [Background technology]

[0002] In recent years, automobiles have been equipped with on-board cameras to assist with parking and prevent collisions through image recognition, and attempts have also been made to apply this to autonomous driving. Camera modules such as these 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 this lens group, and an aperture member arranged between at least one of the lenses in the lens group (see, for example, Patent Document 1).

[0003] In a lens unit, generally, multiple lenses are stacked and assembled inside the lens barrel, and finally, a cap is attached to the object-side end of the lens barrel or the object-side end of the lens barrel is crimped to hold the lens group consisting of the laminated lenses in the optical axis direction inside the lens barrel. In this case, particularly in an in-vehicle camera, the lens positioned closest to the object that can be exposed to the outside is often made of glass, and the other inner lenses are often made of resin. In particular, when a resin lens is assembled inside a resin lens barrel, the lens is generally fitted into the lens barrel in a light press-fit state with a predetermined diameter difference to prevent the lens from shifting due to vibration, impact, etc., resulting in degradation of resolution performance or misalignment of the optical axis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-231993 Summary of the Invention [Problem to be solved by the invention]

[0005] In a lens unit in which a plastic lens is press-fitted into a plastic lens barrel, radially inward compressive stress constantly acts on the lens when the lens is assembled. Therefore, if there is a difference between the linear expansion coefficient (thermal expansion coefficient) of the lens barrel and that of the lens, particularly in the case of a typical lens barrel made of a material such as fiber-reinforced polyamide and a lens made of unreinforced polycarbonate resin, where the lens has a higher linear expansion coefficient and a lower flexural modulus than the lens barrel, this difference causes the lens to expand in a high-temperature environment so that its outer diameter exceeds its inner diameter. The lens, which has nowhere to displace radial deformation, experiences permanent deformation (plastic deformation) in the optical axis direction on the surface facing the optical axis. Such lens deformation at high temperatures can adversely affect optical properties, such as reducing the desired resolution or causing focus shifts.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a lens unit, a camera module, an on-board system, and a vehicle that can reduce deformation of the lens in the optical axis direction due to the difference in linear expansion coefficient between the lens barrel and the lens. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides a lens unit including: a cylindrical lens barrel that forms an internal storage space for storing and holding lenses; and a lens group that is incorporated into the internal storage space of the lens barrel and that is made up of a plurality of lenses arranged along an optical axis, at least one lens constituting the lens group is a resin lens formed of resin, the resin lens having a linear expansion coefficient greater than that of the lens barrel, and is incorporated into the inner accommodation space by press-fitting; A buffer layer is interposed between the radially outer peripheral surface of the resin lens and the inner surface of the lens barrel, which absorbs and relieves the compressive stress acting on the resin lens toward the radially inward direction.

[0008] According to the above-mentioned configuration of the present invention, a buffer layer is interposed between the radially outer peripheral surface of the resin lens and the inner surface of the lens barrel, which absorbs and relieves the compressive stress acting on the resin lens in the radially inward direction. Therefore, even if the resin lens, which is pressed into the inner storage space of the lens barrel and is constantly subjected to compressive stress in the radially inward direction and has a linear expansion coefficient greater than that of the lens barrel, attempts to expand and deform in the radially outward direction under high-temperature conditions, the deformation is at least partially absorbed by the buffer layer, and therefore the resin lens does not deform so much in the radial direction that it has nowhere to go and becomes permanently deformed (plastically deformed) in the optical axis direction. In other words, deformation of the resin lens in the optical axis direction is suppressed (reduced), and therefore the desired optical characteristics can be maintained even at high temperatures.

[0009] The buffer layer may be made of any material as long as it can relieve the compressive stress acting radially inward, which causes deformation of the resin lens in the optical axis direction. However, to effectively and reliably relieve the compressive stress, it is preferable that the buffer layer be made of a low-elasticity material, such as elastomer or rubber, or a soft material with a high heat resistance temperature (preferably 130°C or higher). In this case, the buffer layer may be separate from the lens barrel and the resin lens, or may be integrated with them. Furthermore, if the buffer layer is separate from the resin lens, it may be provided individually in correspondence with the portion of the lens barrel where the resin lens is located, or it may be provided over almost the entire inner surface of the lens barrel (for example, over the entire inner surface of the lens barrel except for the portion of the lens barrel where the lens closest to the object, such as a glass lens, is located). Furthermore, the thickness of the buffer layer is determined by the dimension of the resin lens in the optical axis direction (thickness dimension) and the dimension in the radial direction (outer diameter), the position of the resin lens within the lens barrel, the outer diameter of the lens barrel, etc., and may be set to, for example, 0.6 to 1.5 mm, and may be maintained at a constant dimension throughout, or may gradually (continuously or stepwise) increase or decrease from the object side toward the image side.

[0010] Furthermore, in the above-described configuration of the present invention, when the lens barrel is made of resin, it is preferable that the flexural modulus of the buffer layer be smaller than that of the lens barrel. In this case, it is even more preferable that the flexural modulus of the resin lens be smaller than that of the lens barrel, and that the flexural modulus of the buffer layer be smaller than that of the resin lens. In other words, it is even more preferable that the magnitude relationship of the flexural moduli is: flexural modulus of lens barrel > flexural modulus of resin lens > flexural modulus of buffer layer. This allows the buffer layer to reliably and sufficiently absorb and alleviate the compressive stress acting on the resin lens in the radially inward direction. Here, "made of resin" for a lens barrel means that resin is the main component (at least 20% by weight), and may also contain other materials such as glass filler.

[0011] In the above-described configuration of the present invention, the flexural modulus of the buffer layer is 550 to 2500 MPa (N / mm 2 ) is preferable. This makes it possible to reduce the deformation of the resin lens in the optical axis direction by at least 2%, although this depends on the shape of the resin lens. The flexural modulus can be measured based on the JIS standard (JIS K7171).

[0012] In the above-described configuration of the present invention, the buffer layer may be integrated with the lens barrel or the resin lens. This allows for easy assembly of the lens into the lens barrel and ensures reliable and stable positioning of the buffer layer. The lens barrel and the buffer layer can be integrated by insert molding, for example. In this case, the lens barrel has a two-layer structure consisting of a base layer and a buffer layer.

[0013] The present invention also provides a camera module having the lens unit described above, an in-vehicle system having the camera module, and a vehicle equipped with the in-vehicle system, which can achieve the same effects as the lens unit described above. [Effects of the Invention]

[0014] According to the present invention, a buffer layer is interposed between the radially outer peripheral surface of the resin lens and the inner surface of the lens barrel, which absorbs and relieves the compressive stress acting on the resin lens toward the radially inner side. This reduces deformation of the lens in the optical axis direction due to the difference in the linear expansion coefficient between the lens barrel and the lens. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view (cross-sectional view along the optical axis) of a lens unit according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a main part of FIG. [Figure 3] 10 is a cross-sectional view showing an embodiment in which a buffer layer is provided on the inner surface of a lens barrel by insert molding, showing a state in which a buffer member that forms the buffer layer is attached to a movable-side mold. FIG. [Figure 4] 4 is a cross-sectional view showing the state in which the mold is closed in the embodiment of FIG. 3 to define a cavity into which molten resin is poured. FIG. [Figure 5] 10 is a table showing an example of material properties of a lens barrel, a resin lens, and a buffer layer. [Figure 6] 10 is a table showing test results of the displacement amount of the center of the resin lens in the optical axis direction. [Figure 7] 2 is a schematic cross-sectional view of a camera module having the lens unit of FIG. 1. [Figure 8] 1 is a schematic diagram of a vehicle equipped with an in-vehicle system including a camera module according to an embodiment of the present invention. [Figure 9] 9 is a block diagram showing the configuration of an imaging device that constitutes the in-vehicle system of FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment can realize a highly reliable system, particularly in a sensing system, and contributes to the development of resilient infrastructure. The target is "9.1 Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all," which is one of the Sustainable Development Goals (SDGs) advocated by the United Nations. The lens unit of the present embodiment described below is particularly intended for use as a camera module for an in-vehicle camera or the like, and is fixedly installed on the exterior surface of the vehicle, with wiring drawn into the vehicle and connected to a display or other device. Furthermore, hatching of multiple lenses is omitted in Figures 1 and 7.

[0017] FIG. 1 shows a lens unit 11 according to one embodiment of the present invention. As shown, the lens unit 11 of this embodiment includes a cylindrical lens barrel 12, a plurality of lenses (e.g., 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) arranged within a stepped inner storage space S of the lens barrel 12, and an aperture member 22. The aperture member is either an "aperture diaphragm" that limits the amount of transmitted light and determines the F-number, which is an index of brightness, or an "optical diaphragm" that blocks light rays that cause ghosting or aberrations. An in-vehicle camera equipped with such lens unit 11 includes the lens unit 11, a circuit board (not shown) having an image sensor, and an installation member (not shown) for installing the circuit board in a vehicle such as an automobile. In this embodiment, the first lens 13 that can be exposed to the outside is a glass lens, and the other inner lenses 14, 15, 16, and 17 are all resin lenses made of resin (plastic), but this is not limiting. Also, the lens barrel 12 that houses these lenses 13, 14, 15, 16, and 17 is made of resin in this embodiment, but it may also be made of metal. The shapes of the lens barrel and lenses, the number of lenses, and so forth can be set as desired depending on the application, etc.

[0018] 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 aligned along a single optical axis O to form a group of lenses L used for imaging. Of these, the two lenses 16 and 17, the fourth and fifth lenses located closest to the image (the innermost side of the inner storage space S), are, for example, cemented lenses. Furthermore, the surfaces of these lenses 13, 14, 15, and 16 may be coated with an anti-reflection film, a hydrophilic film, a water-repellent film, or the like, as necessary.

[0019] At the object side end (the upper end in Figure 2) of the lens barrel 12, a crimped portion 23 is provided by crimping the end radially inward, and this crimped portion 23 fixes the first lens 13, which is positioned closest to the object side of the lens group L, to the object side end of the lens barrel 12.

[0020] Furthermore, an inner flange portion 24 having an opening with a diameter smaller than that of fifth lens 17 is provided at the end (the lower end in FIG. 2) of lens barrel 12 on the image side. This inner flange portion 24 and crimped portion 23 hold multiple lenses 13, 14, 15, 16, and 17 that make up lens group L and diaphragm member 22 within lens barrel 12.

[0021] The outer peripheral surface of first lens 13, which is positioned closest to the object, has a tapered portion with a reduced diameter on the image-side portion of lens 13, and an O-ring 26 serving as a seal member is provided in this tapered portion, sealing the gap between the outer peripheral surface of lens 13 and the inner peripheral surface of lens barrel 12 at the object-side end of lens barrel 12. This prevents water, dust, and other fine particles from entering lens barrel 12 from the object-side end of lens unit 11. The seal member interposed between first lens 13 and lens barrel 12 is not limited to an O-ring, and can be any form of an annular body that can seal the gap between first lens 13 and lens barrel 12.

[0022] The inner and outer diameters of lens barrel 12 decrease in stages from the object side to the image side. That is, lens barrel 12 has a large-diameter section 12A that houses and holds first and second lenses 13 and 14, and a small-diameter section 12B that houses and holds third, fourth, and fifth lenses 15, 16, and 17. Corresponding to the stepped shape of lens barrel 12, the outer diameters of lenses 13, 14, 15, 16, and 17 decrease from the object side to the image side. An outer flange 25 is provided on the outer peripheral surface of lens barrel 12 in the shape of a brim and is used when installing lens barrel 12 in an in-vehicle camera.

[0023] Furthermore, in this embodiment, the linear expansion coefficients of resin lenses 14, 15, 16, and 17 are larger than that of lens barrel 12, and, except for resin lens 16 on the object side of the cemented lens, they are incorporated by press-fitting into inner storage space S of lens barrel 12. As shown in enlarged view in Figure 2, buffer layer 30 is interposed between radially outer peripheral surfaces 14a, 15a, and 17a of press-fitted resin lenses 14, 15, and 17 and inner surface 12a of lens barrel 12, and absorbs and relieves compressive stress acting radially inward on resin lenses 14, 15, and 17.

[0024] In this case, as shown in the table of FIG. 5, the lens barrel 12 is made of an anisotropic material made of fiber-reinforced polyamide (PA), and its linear expansion coefficient is about 6×10 in the flow direction. -5 / ℃, approximately 1×10 in the perpendicular direction (perpendicular direction) -5 / ℃ (average approx. 3.5 × 10 -5 / °C) and has a heat resistance temperature of 130°C or higher. The resin lenses (plastic lenses) 14, 15, 16, and 17 are made of an isotropic material such as polycarbonate (PC) or cycloolefin polymer (COP), and have a linear expansion coefficient of about 6×10 -5 / °C and has a heat resistance temperature of 130°C or higher. The buffer layer 30 is made of an isotropic material consisting of a low elastic modulus material such as elastomer or rubber, or a soft material, and its linear expansion coefficient is approximately 20×10 -5 / °C and has a heat resistance temperature of 130°C or higher. Here, "heat resistance temperature" refers to the higher of the deflection temperature under load or the glass transition temperature.

[0025] The buffer layer 30 is separate from the lenses 13-17 and the lens barrel 12, and may be provided individually corresponding to the internal portion of the lens barrel 12 where the resin lenses 14, 15, and 17 pressed into the internal storage space S are located. However, in this embodiment, the buffer layer 30 extends over almost the entire inner surface 12a of the lens barrel 12, specifically, over the entire inner surface 12a of the lens barrel 12 except for the internal portion of the lens barrel 12 where the first glass lens 13 closest to the object in the lens group L is located. In particular, buffer layer 30 according to this embodiment is formed of a substantially cylindrical buffer material having steps whose inner and outer diameters gradually decrease from the object side to the image side so as to fit the shape of inner surface 12a of lens barrel 12. Its thickness is determined by the dimensions (thickness) and radial dimensions (outer diameter) of resin lenses 14, 15, 16, and 17 in the optical axis direction, the positions of resin lenses 14, 15, 16, and 17 within lens barrel 12, the outer diameter of the lens barrel, and the like, and is set to, for example, 0.6 to 1.5 mm, but in this embodiment in particular, a constant dimension is maintained throughout. However, for example, the thickness of buffer layer (buffer material) 30 may gradually (continuously or stepwise) increase or decrease from the object side to the image side in accordance with the decrease in the outer diameter of lenses 13-17 from the object side to the image plane side.

[0026] In this embodiment, the buffer layer 30 is separate from the lenses 13-17 and the barrel 12; however, the buffer layer 30 may be integral with the barrel 12 or the lenses 13-17. In particular, the integration of the buffer layer 30 with the barrel 12 can be achieved, for example, by insert molding. An example in which the buffer layer 30 is provided on the inner surface 12a of the barrel 12 by insert molding is shown in FIGS. 3 and 4. In this type of insert molding, as shown in FIG. 3, a buffer member 30 serving as a buffer layer is prepared in advance and attached to the movable mold part 40B of the mold 40. Then, the movable mold part 40B is assembled to the fixed mold part 40A. The mold 40 is then closed as shown in FIG. 4 to define a cavity C into which molten resin is poured. In this state, molten resin is then poured into cavity C through gate 42 of fixed mold portion 40A, and after hardening, movable mold portion 40B is removed and the molded product is pushed out of fixed mold portion 40A using an ejection pin or the like (not shown), thereby completing lens barrel 12 having a two-layer structure consisting of a lens barrel base layer and a buffer layer 30.

[0027] In this embodiment, the flexural modulus of the buffer layer 30 is smaller than that of the lens barrel 12, the flexural modulus of the resin lenses 14, 15, 16, and 17 is smaller than that of the lens barrel 12, and the flexural modulus of the buffer layer 30 is smaller than that of the resin lenses 14, 15, 16, and 17. In other words, the magnitude relationship of the flexural moduli satisfies the relationship: flexural modulus of the lens barrel 12 > flexural modulus of the resin lenses 14, 15, 16, and 17 > flexural modulus of the buffer layer 30. Specifically, in this embodiment, the flexural modulus of the lens barrel 12 is 13,900 MPa (N / mm 2 ), the flexural modulus of the resin lenses 14, 15, 16, and 17 is set to 2540 MPa, and the flexural modulus of the buffer layer 30 is set to 550 to 2500 MPa.

[0028] When the flexural modulus of the buffer layer 30 is set within this range, the amount of deformation of the resin lenses 14, 15, 16, and 17 in the optical axis direction can be reduced by at least 2%, depending on the shape of the resin lenses 14, 15, 16, and 17. Test results that demonstrate this are shown in FIG. 6. In this test, the lens barrel 12 was formed from a resin material (in this embodiment, "RENNY" (trademark) was used) in which 30% by weight of glass filler (GF) was mixed into the main component polyamide (PA), and the buffer layer 30 was formed from a highly heat-resistant elastomer (in this embodiment, "Hytrel 7247" (trademark) was used). Furthermore, the third lens 15 and the fifth lens 17 were press-fitted into the lens barrel 12 without the buffer layer 30. The centers of the object-side surfaces (positions A and C in FIG. 1) and the image-side (image-forming surface) surfaces of the third lens 15 and the fifth lens 17 were measured. The amount of displacement in the optical axis direction at each of the object-side surface centers (positions A and C in FIG. 1) and the image-side (image plane side) surface centers (positions B and D in FIG. 1) of the third lens 15 and the fifth lens 17 press-fitted into the lens barrel 12 with the buffer layer 30 was measured under temperature conditions of 125°C and 25°C (first row in the table in FIG. 6). The amount of displacement in the optical axis direction at each of the object-side surface centers (positions A and C in FIG. 1) and the image-side (image plane side) surface centers (positions B and D in FIG. 1) of the third lens 15 and the fifth lens 17 press-fitted into the lens barrel 12 with the buffer layer 30 was measured under temperature conditions of 125°C and 25°C (second row in the table in FIG. 6). The percentage values (%) shown below the amount of displacement are values when the amount of displacement of each of the lenses 15 and 17 in the lens barrel 12 without the buffer layer 30 is set to 100%, and the signs indicate a decrease in the amount of displacement with a minus sign. For example, at the center (position D) of the image-side surface of the fifth lens 17 in the lens barrel 12 without the buffer layer 30, a certain displacement amount is exhibited under a temperature condition of 25°C, and if this is taken as 100% (the displacement amount when the buffer layer 30 is not present is taken as 100%), at the center (position D) of the image-side surface of the fifth lens 17 in the lens barrel 12 with the buffer layer 30, the displacement amount is reduced by 69.3% under a temperature condition of 25°C (the minus sign indicates the effect of reducing the displacement amount).

[0029] In this test, the bending modulus of the lens barrel 12 was 13900 N / mm 2 and the flexural modulus of the buffer layer 30 is 550 N / mm 2The thickness of the buffer layer 30 was set to 0.7 mm. Furthermore, in the lens barrel 12 with the buffer layer 30, the bending elastic modulus of the buffer layer 30 was set to 1000 N / mm 2 , 1500N / mm 2 , 2500N / mm 2 The displacement amounts at the centers of the object-side and image-side surfaces of the third lens 15 and the fifth lens 17 were calculated at 125° C. and 25° C. (third row of the table).

[0030] As can be seen from the results in Figure 6, when a buffer layer 30 is included, the displacement of the resin lens in the optical axis direction is suppressed compared to when a buffer layer 30 is not included, provided that the flexural modulus is at least within the range of 550 to 2500 MPa, and the suppression effect is greater the smaller the flexural modulus (the softer the layer).

[0031] 7 shows a schematic cross-sectional view of a camera module 300 according to the present embodiment, which has a lens unit 11 configured as described above. As shown in the figure, this camera module 300 includes the lens unit 11 of FIG. 2 to which a 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 sealing 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 the other portions. Mount 302 is disposed inside upper case 301, and has female threads 302a that mesh with 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 12b 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 positioned to receive the image of the 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 are components of the image data captured by the camera.

[0035] FIG. 8 schematically illustrates a vehicle 40 equipped with an in-vehicle system including an imaging device 50 including the camera module 300 of FIG. 7 . As illustrated, the imaging device 50 can be mounted on the vehicle 40, and FIG. 8 illustrates an example of the mounting position of the imaging device 50 on the vehicle 40. The imaging device 50 mounted on the vehicle 40 can also be called an in-vehicle camera and can be installed in various locations on the vehicle 40. For example, the first imaging device 50a may be installed on or near the front bumper as a camera that monitors the front of the vehicle 40 while the vehicle 40 is traveling. The second imaging device 50b that monitors the front may be installed near an inner rearview mirror inside the vehicle 40. The third imaging device 50c may be installed on the dashboard or in the instrument panel as a camera that monitors the driver's driving status. The fourth imaging device 50d may be installed at the rear of the vehicle 40 to monitor the rear of the vehicle 40. The imaging devices 50a and 50b can be called front cameras. The third imaging device 50c can be called an in-camera. The fourth imaging device 50d can be called a rear camera. The imaging device 50 is not limited to these, and can include imaging devices installed in various positions, such as a left side camera that captures images of the left rear side and a right side camera that captures images of the right rear side.

[0036] An image signal of an image captured by the imaging device 50 may be output to an information processing device 42 and / or a display device 43, etc., within the vehicle 40. The information processing device 42 and the display device 43, together with the imaging device 50, constitute an in-vehicle system. The information processing device 42 within the vehicle 40 includes a device that processes the image signal acquired by the imaging device 50, recognizes the image, and assists the driver in driving. The information processing device 42 may include, but is not limited to, a navigation system, a collision damage mitigation braking system, a vehicle-to-vehicle distance control device, and a lane departure warning system. The display device 43 displays the image processed and output by the information processing device 42, but can also receive the image signal directly from the imaging device 50. The display device 43 may be, but is not limited to, a liquid crystal display (LCD), an organic electroluminescence (EL) display, or an inorganic EL display. The display device 43 can display to the driver an image signal output from the imaging device 50, which captures an image from a position difficult for the driver to view, such as a rear camera.

[0037] Fig. 9 shows the configuration of an imaging device that constitutes the in-vehicle system of Fig. 8. As shown in the figure, imaging device 50 according to one embodiment includes control unit 52, storage unit 54, and camera module 300 shown in Fig. 7 described above.

[0038] The control unit 52 controls the camera module 300 and processes the electrical signal output from the image sensor 304 of the camera module 300. The control unit 52 may be configured as, for example, a processor. The control unit 52 may also include one or more processors. The processor may include a general-purpose processor that loads a specific program to execute a specific function, and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific integrated circuit (IC). An application-specific IC is also called an application-specific integrated circuit (ASIC). The processor may include a programmable logic device. A programmable logic device is also called a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 52 may be either a system-on-a-chip (SoC) or a system in a package (SiP) in which one or more processors work together.

[0039] The storage unit 54 stores various information or parameters related to the operation of the imaging device 50. The storage unit 54 may be configured with, for example, a semiconductor memory or the like. The storage unit 54 may function as a work memory for the control unit 52. The storage unit 54 may store captured images. The storage unit 54 may store various parameters, etc., used by the control unit 52 to perform detection processing based on the captured images. The storage unit 54 may be included in the control unit 52.

[0040] As described above, the camera module 300 captures an image of a subject formed via the lens unit 11 with the image sensor 304 and outputs the captured image. The image captured by the camera module 300 is also referred to as a captured image.

[0041] The image sensor 304 may be configured, for example, as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device). The image sensor 304 has an imaging surface on which a plurality of pixels are arranged. Each pixel outputs a signal specified by a current or voltage according to the amount of incident light. The signal output by each pixel is also referred to as imaging data.

[0042] The imaging data may be read by the camera module 300 for all pixels and imported into the control unit 52 as a captured image. A captured image read out for all pixels is also referred to as a maximum captured image. The imaging data may be read by the camera module 300 for some pixels and imported as a captured image. In other words, the imaging data may be read out from pixels in a predetermined capture range. The imaging data read out from pixels in the predetermined capture range may be imported as a captured image. The predetermined capture range may be set by the control unit 52. The camera module 300 may acquire the predetermined capture range from the control unit 52. The imaging element 304 may capture an image of a predetermined capture range from the subject image formed via the lens unit 11.

[0043] As described above, according to this embodiment, the buffer layer 30 that absorbs and relieves the compressive stress acting radially inward on the resin lenses 14, 15, 17 is interposed between the radially outer peripheral surfaces 14a, 15a, 17a of the resin lenses 14, 15, 17 and the inner surface 12a of the lens barrel 12. Therefore, even if the resin lenses 14, 15, 17, which are pressed into the inner storage space S of the lens barrel 12 and are constantly subjected to compressive stress acting radially inward and have a linear expansion coefficient greater than that of the lens barrel 12, attempt to expand and deform radially outward in a high-temperature environment, the deformation is at least partially absorbed by the buffer layer 30. Therefore, the resin lenses 14, 15, 17 are prevented from deforming so much in the radial direction that they become trapped and undergo permanent deformation (plastic deformation) in the optical axis direction. In other words, deformation of the resin lenses 14, 15, 17 in the optical axis direction is suppressed (reduced), and therefore the desired optical characteristics can be maintained even at high temperatures.

[0044] The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the shapes of the lenses and lens barrels in the present invention are not limited to those in the above-described embodiments. Furthermore, some or all of the above-described embodiments may be combined, or part of the configuration of one of the above-described embodiments may be omitted, without departing from the spirit of the present invention. [Explanation of symbols]

[0045] 11 Lens unit 12 Telescope tube 12a Inner surface 14,15,16,17,18 Resin lenses 14a, 15a, 17a: radially outer peripheral surface 30 Buffer layer 40 vehicles 42 Information processing equipment (processing equipment) 43 Display device 50 Imaging device 52 Control section 300 Camera Module 304 Image sensor L lens group S Inner storage space

Claims

1. A lens unit comprising: a cylindrical lens barrel that forms an internal storage space for storing and holding lenses; and a lens group that is incorporated into the internal storage space of the lens barrel and that is composed of a plurality of lenses arranged along an optical axis, at least two lenses constituting the lens group are resin lenses formed of resin, the resin lenses have a linear expansion coefficient greater than that of the lens barrel, and are press-fitted into the inner housing space so as to be stacked one on top of the other; a buffer layer is interposed between a radially outer peripheral surface of the resin lens and an inner surface of the lens barrel, the buffer layer absorbing and alleviating compressive stress acting on the resin lens toward the radially inner side; A lens unit characterized in that the buffer layer extends continuously over the entire inner surface of the lens barrel on which all of the resin lenses stacked one on top of another are located, so as to conform to the shape of the inner surface.

2. 2. The lens unit according to claim 1, wherein the lens barrel is made of resin, and the buffer layer has a flexural modulus smaller than that of the lens barrel.

3. 3. The lens unit according to claim 2, wherein the resin lens has a lower flexural modulus than the lens barrel, and the buffer layer has a lower flexural modulus than the resin lens.

4. 4. The lens unit according to claim 1, wherein the buffer layer has a flexural modulus of elasticity of 550 to 2500 MPa.

5. 5. The lens unit according to claim 1, wherein the buffer layer is integral with the lens barrel or the resin lens.

6. A camera module comprising: the lens unit according to claim 1; and an image sensor that converts light collected through a lens group of the lens unit into an electric signal.

7. An in-vehicle system mounted on a vehicle, an imaging device comprising: the camera module according to claim 6; and a control unit that controls the camera module and processes an electrical signal output from the imaging element of the camera module; a processing device that processes an image signal acquired by the imaging device; a display device that displays an image processed and output by the processing device; An in-vehicle system comprising:

8. A vehicle equipped with the on-board system according to claim 7.

Images