Imaging device

Abstract

This imaging device comprises: an imaging element; a housing that holds the imaging element; a member that has a linear expansion coefficient different from that of the housing; and a plurality of fixing parts that fix the member to the housing. The housing has a component storage part that forms a space for storing an electric component. The component storage part is provided at a position offset in the longitudinal direction of the housing with respect to the housing's center line extending along the lateral direction of the housing through the center of the housing with an imaging direction as a front direction. The plurality of fixing parts include a first rear side fixing part and a second rear side fixing part that fix the rear side of the member to the housing. The first rear side fixing part is disposed in the offset direction of the component storage part with respect to the component storage part, the second rear side fixing part is disposed in a direction opposite to the offset direction of the component storage part with respect to the component storage part, and the distance from the center line to the second rear side fixing part is shorter than the distance from the center line to the first rear side fixing part.

Description

Imaging device

[0001] The present invention relates to an imaging device.

[0002] In recent years, vehicles have increasingly been equipped with driver assistance systems in an effort to realize a safe and comfortable motorized society. Among these, development is progressing on systems that pursue safety, convenience, and comfort for drivers and passengers, such as collision mitigation braking systems that automatically decelerate and stop a vehicle before colliding with an obstacle, automatic vehicle distance control systems that automatically follow a preceding vehicle while maintaining a safe distance, lane departure prevention systems, and sign recognition. One such system is an external environment recognition system that recognizes vehicles, pedestrians, etc. and measures the distance to the target object.

[0003] A known external world recognition system is a system equipped with a stereo camera (image capture device). In this external world recognition system, a pair of images captured by the stereo camera are processed to extract common feature points between the images. The system then calculates the distance by using an integrated circuit to determine the number of pixels (parallax) by which the feature points are displaced between the pair of images. Therefore, any misalignment between the pair of images other than the inherent parallax can result in an error in the distance measurement results. One cause of this misalignment is optical axis misalignment due to thermal deformation caused by differences in the amount of expansion of individual components when temperatures rise due to sunlight or heat generated by electrical components within the image capture device. Optical axis misalignment refers to the optical axis (center) of an optical component, such as a lens or image sensor, being tilted or offset from its reference position in the design.

[0004] A technique for preventing a decrease in measurement accuracy due to thermal deformation (expansion and contraction) of a housing caused by temperature changes is known (see Patent Document 1). Patent Document 1 discloses a structure in which a housing (camera case) holds a substrate via a pressing member (spring cylinder, air cylinder).

[0005] Japanese Patent Application Laid-Open No. 2019-201262

[0006] In order to reduce the size of an imaging device, the imaging device may be formed into an asymmetric shape. When the housing of the imaging device is formed into an asymmetric shape, thermal deformation of the housing due to temperature changes may cause a large deviation in the optical axis of the imaging element fixed to the housing. The technology described in Patent Document 1 requires a complex holding structure such as a spring cylinder or an air cylinder, which poses problems of increased risk of failure and cost.

[0007] An object of the present invention is to provide an imaging device that has a low risk of failure, is low cost, and is capable of reducing optical axis deviation.

[0008] An imaging device according to one aspect of the present invention comprises an imaging element, a housing for holding the imaging element, a member having a linear expansion coefficient different from that of the housing and arranged along the longitudinal direction of the housing, and a plurality of fixing portions for fixing the member to the housing, wherein the housing has a component storage portion that forms a space for storing electrical components, and the component storage portion is provided at a position offset in the longitudinal direction of the housing with respect to a center line of the housing that extends along the lateral direction of the housing, passing through the center of the housing, with the imaging direction of the imaging element being the front, and by having the component storage portion, the housing The member is formed in an asymmetrical shape with respect to the center line, and the multiple fixing portions include a first rear fixing portion and a second rear fixing portion that fix the rear side of the member to the housing, the component storage portion is arranged between the first rear fixing portion and the second rear fixing portion, the first rear fixing portion is arranged in an offset direction of the component storage portion with respect to the component storage portion, the second rear fixing portion is arranged in a direction opposite to the offset direction of the component storage portion with respect to the component storage portion, and the distance from the center line to the second rear fixing portion is shorter than the distance from the center line to the first rear fixing portion.

[0009] According to the present invention, it is possible to provide an imaging device that has a low risk of failure, low cost, and is capable of reducing optical axis deviation.

[0010] FIG. 1 is a perspective view of the appearance of an imaging device according to a first embodiment. FIG. 2 is a see-through perspective view of an imaging device according to the first embodiment. FIG. 3 is a schematic plan cross-sectional view of an imaging device according to the first embodiment. FIG. 4 is a see-through perspective view of an imaging device according to a comparative example of this embodiment. FIG. 5 is a schematic plan cross-sectional view of an imaging device according to a comparative example of this embodiment. FIG. 6 is a perspective view of an imaging device according to a comparative example of this embodiment after deformation. FIG. 7 is a diagram illustrating thermal deformation in various directions of an imaging device according to a comparative example of this embodiment. FIG. 8 is a diagram illustrating the relationship between the relative displacement of the first optical axis and the second optical axis when a predetermined temperature change occurs and the distance from the center line of the housing to the second rear fixed part. FIG. 9 is a schematic plan cross-sectional view of an imaging device according to a second embodiment. FIG. 10 is a schematic plan cross-sectional view of an imaging device according to a third embodiment. FIG. 11 is a schematic plan cross-sectional view of an imaging device according to a fourth embodiment. FIG. 12 is a schematic rear cross-sectional view of a fixed part of an imaging device according to a fifth embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Components with the same reference numerals have the same functions. Therefore, unless otherwise specified, if a description has already been given, the description will be omitted. An imaging device according to this embodiment is mounted on a vehicle such as a four-wheeled motor vehicle or a two-wheeled motor vehicle. The imaging device continuously captures images of the area ahead of the vehicle and recognizes the position and speed of objects (other vehicles, pedestrians, etc.) present in the vehicle's direction of travel based on changes in the images over time.

[0012] First Embodiment A first embodiment of the present invention will be described with reference to Figures 1 to 8. Figure 1 is an external perspective view of an imaging device 100, and Figure 2 is a see-through perspective view of the imaging device 100. Note that the x-axis, y-axis, and z-axis shown in the figures represent the three axes of a three-dimensional Cartesian coordinate system. In other words, the x-axis, y-axis, and z-axis are mutually orthogonal.

[0013] The z-axis is an axis along the front-to-rear direction of the imaging device 100 (i.e., the front-to-rear direction of the vehicle in which the imaging device 100 is mounted). On the z-axis, the front, which is the imaging direction of the imaging device 100 (the imaging direction of the imaging element 2), is considered positive, and the rear of the imaging device 100 is considered negative. The y-axis is an axis along the up-and-down direction of the imaging device 100 (i.e., the up-and-down direction of the vehicle in which the imaging device 100 is mounted). On the y-axis, the top of the imaging device 100 is considered positive, and the bottom of the imaging device 100 is considered negative. The x-axis is an axis along the left-to-right direction of the imaging device 100 (i.e., the left-to-right direction of the vehicle in which the imaging device 100 is mounted). On the x-axis, the left side of the imaging device 100 is considered positive, and the right side of the imaging device 100 is considered negative.

[0014] 1 and 2 , the imaging device 100 includes a rectangular box-shaped housing 101 that is open on the lower surface (bottom surface) and rear surface (back surface), imaging modules 5 (first imaging module 5a and second imaging module 5b) housed inside the housing 101, and a circuit board 107 housed inside the housing 101. The housing 101 is made of metal (for example, aluminum die-cast), and is provided with heat dissipation fins 113 on its top surface.

[0015] The first imaging module 5a includes a first lens 4a, a first imaging element 2a, a first imaging board 3a on which the first imaging element 2a is mounted, and a first module holder (not shown) that secures these together. The second imaging module 5b includes a second lens 4b, a second imaging element 2b, a second imaging board 3b on which the second imaging element 2b is mounted, and a second module holder (not shown) that secures these together. Hereinafter, the optical axis of the first imaging module 5a (i.e., the optical axis of the first lens 4a and the first imaging element 2a) will be referred to as the first optical axis 6a, and the optical axis of the second imaging module 5b (i.e., the optical axis of the second lens 4b and the second imaging element 2b) will be referred to as the second optical axis 6b. The first imaging module 5a and the second imaging module 5b are held in a housing 101.

[0016] The imaging boards (3a, 3b) are connected to a circuit board 107 via flexible wiring members such as FPCs (flexible printed circuits) or FFCs (flexible flat cables). The circuit board 107 processes images captured by the imaging elements (2a, 2b) of the imaging module 5. The circuit board 107 is formed of a material different from that of the housing 101. For example, the circuit board 107 is configured as a printed circuit board in which an insulating base material containing a synthetic resin such as glass epoxy and a wiring pattern such as copper foil are laminated. Therefore, the circuit board 107 and the housing 101 have different linear expansion coefficients (thermal expansion coefficients). In this embodiment, the linear expansion coefficient of the housing 101 is greater than the linear expansion coefficient of the circuit board 107.

[0017] A plurality of circuit elements (such as a first circuit element 111 and a second circuit element 112) are mounted on the circuit board 107. The first circuit element 111 includes a microcomputer that processes image signals, a signal processing element, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), and the like. The second circuit element 112 includes a memory used for temporary data storage, and the like. The plurality of circuit elements may include circuit elements that perform various types of signal processing, such as an MPU (Micro Processing Unit), and large circuit elements such as capacitors.

[0018] After the imaging module 5 and circuit board 107 are mounted in the housing 101, the openings on the bottom and rear of the housing 101 are closed with covers (not shown) made of aluminum or the like. The circuit board 107 and imaging board 3 are enclosed by the metal housing 101 and covers (bottom cover and rear cover). This ensures dustproofness of the imaging device 100 and blocks electrical influences from the outside to the inside of the imaging device 100 (electromagnetic field countermeasures). Furthermore, the metal housing 101 is provided with fins 113 for heat dissipation. Therefore, the imaging device 100 also has excellent heat dissipation properties to the outside.

[0019] The circuit board 107 of the imaging device 100 is electrically connected to the vehicle's ECU (Electronic Control Unit). The imaging device 100 and the ECU are electrically connected by connecting wiring to an electrical connector 114 provided on the upper surface of the circuit board 107. The electrical connector 114 is electrically connected to the wiring pattern of the circuit board 107. Note that a rear cover that covers the opening on the rear surface of the housing 101 has an opening for connecting wiring from the ECU to the electrical connector 114. An output signal from the circuit board 107 is transmitted to the ECU via the wiring and is used for vehicle control by the ECU.

[0020] The electrical connector 114 is a relatively large electrical component among the components mounted on the imaging device 100. For this reason, in this embodiment, a component storage section 115 for storing the electrical connector 114 attached to the upper surface of the circuit board 107 is formed in the housing 101. The component storage section 115 functions as a space forming section that forms a rectangular parallelepiped space (storage space) for storing the electrical connector 114. The storage space is formed between the circuit board 107 and the housing 101.

[0021] The component storage section 115 is formed at the rear end of the housing 101. The component storage section 115 is formed in the shape of a rectangular box (concave shape) with an open bottom (lower surface) and back (rear surface). The component storage section 115 has an upper wall surface facing the top surface of the electrical connector 114, a right side wall surface 15R (see FIG. 3) facing the right side surface of the electrical connector 114, a left side wall surface 15L (see FIG. 3) facing the left side surface of the electrical connector 114, and a front side wall surface 15F (see FIG. 3) facing the front surface of the electrical connector 114. A gap is formed between the wall surfaces of the component storage section 115 and the outer surface of the electrical connector 114.

[0022] The arrangement of the multiple fixing portions 180 that fix the circuit board 107 to the housing 101 will be described with reference to FIG. 3 . FIG. 3 is a schematic plan cross-sectional view of the imaging device 100. In FIG. 3 , the component storage portion 115 that houses the electrical connector 114 attached to the upper surface of the circuit board 107 is indicated by a two-dot chain line. As shown in FIG. 3 , the circuit board 107 is fixed to the housing 101 by the multiple fixing portions 180. The multiple fixing portions 180 each include a fastening member (not shown) such as a screw, a circular insertion hole provided in the circuit board 107 through which the screw is inserted, and a female thread portion (not shown) provided in the housing 101 into which the screw is threaded. Note that the configuration of the fixing portions 180 is not limited thereto. For example, the fixing portions 180 may be configured to fix the circuit board 107 to the housing 101 by crimping, fitting, or the like, using a rivet or a snap fit. The multiple fixing portions 180 include a first rear fixing portion 181 and a second rear fixing portion 182 that fix the rear side of the circuit board 107 to the rear side of the housing 101. The multiple fixing portions 180 also include a first front fixing portion 183 and a second front fixing portion 184 that fix the front side of the circuit board 107 to the front side of the housing 101. The first rear fixing portion 181 and the first front fixing portion 183 are arranged to the right of the center line 9 of the housing 101, and the second rear fixing portion 182 and the second front fixing portion 184 are arranged to the left of the center line 9 of the housing 101.

[0023] The longitudinal direction of the housing 101 is the x-axis direction (left-right direction). The first imaging module 5a is disposed at one longitudinal end (right end) of the housing 101. The second imaging module 5b is disposed at the other longitudinal end (left end) of the housing 101. The circuit board 107 is disposed along the longitudinal direction of the housing 101. The component storage section 115 is disposed to the right of a center line 9 in the left-right direction of the housing 101. The component storage section 115 is provided at a position offset in the longitudinal direction of the housing 101 with respect to the center line 9 of the housing 101. In this embodiment, the component storage section 115 is located only to the right of the center line 9. In other words, the left wall surface 15L, which is the surface of the component storage section 115 closest to the center line 9, is disposed to the right of the center line 9. The center line 9 passes through the center of the housing 101 (the center of the left-right, up-down, and front-to-back directions) and extends along the short side direction (z-axis direction) of the housing 101. The housing 101 has a component storage section 115 and is formed in an asymmetric shape with respect to the center line 9 .

[0024] If the component storage section 115 were provided so as to protrude rearward from the housing 101, the length of the imaging device 100 in the z-axis direction would be large. In this embodiment, the component storage section 115 is located above the circuit board 107 and does not protrude rearward from the housing 101. This allows the length of the imaging device 100 in the z-axis direction to be shortened.

[0025] Various electrical components are mounted on the circuit board 107. For this reason, it may be difficult to set the position of the electrical connector 114 on the center line 9. In this embodiment, the electrical connector 114 is disposed at a position offset by a predetermined distance Xo to the right from the center line 9. For this reason, the component storage section 115 is provided at a position offset by the predetermined distance Xo to the right from the center line 9 so that the electrical connector 114 can be stored therein. In other words, the distance Xo from the center line of the component storage section 115, which halves the left-right width of the component storage section 115, to the center line 9 of the housing 101 corresponds to the offset amount.

[0026] The first rear-side fixing portion 181 and the second rear-side fixing portion 182 are arranged to sandwich the component storage portion 115 from the left and right. In other words, the component storage portion 115 is arranged between the first rear-side fixing portion 181 and the second rear-side fixing portion 182 in the x-axis direction. The first rear-side fixing portion 181 is arranged in the offset direction of the component storage portion 115 (i.e., to the right) relative to the component storage portion 115. The second rear-side fixing portion 182 is arranged in the opposite direction to the offset direction of the component storage portion 115 (i.e., to the left) relative to the component storage portion 115.

[0027] The first front fixing part 183 is provided on an imaginary line that passes through the first rear fixing part 181 and is parallel to the z-axis direction. The first front fixing part 183 and the second front fixing part 184 are disposed in positions that are symmetrical with respect to the center line 9 of the housing 101. In contrast, the first rear fixing part 181 and the second rear fixing part 182 are disposed in positions that are asymmetrical with respect to the center line 9. For this reason, the second front fixing part 184 is not provided on an imaginary line that passes through the second rear fixing part 182 and is parallel to the z-axis direction.

[0028] The fixed part 180 of the imaging device 100 according to the first embodiment is arranged so as to satisfy the following arrangement conditions: (Arrangement condition 1) The distance B in the x-axis direction from the second rear fixed part 182 to the center line 9 is shorter than the distance A in the x-axis direction from the first rear fixed part 181 to the center line 9.

[0029] In this way, in this embodiment, in a configuration in which the component storage section 115 is positioned biased to the right side of the housing 101, the first rear fixing section 181 and the second rear fixing section 182 are positioned so that the distance B from the center line 9 to the second rear fixing section 182 is shorter than the distance A from the center line 9 to the first rear fixing section 181, thereby suppressing optical axis misalignment.

[0030] The imaging device 100 according to this embodiment is a stereo camera equipped with a pair of left and right imaging modules 5a and 5b. The imaging device 100 captures images of the front using the pair of left and right imaging modules 5a and 5b. The imaging device 100 extracts feature points common to both images from the pair of image information, extracts the number of pixels (parallax) where the feature points are misaligned between the pair of images, and calculates distance using an integrated circuit. Therefore, any misalignment between the pair of images other than the inherent parallax can result in errors in the distance measurement results. Furthermore, as imaging devices 100 become more powerful, with wider angles of view, higher accuracy, and faster speeds, the tolerance for misalignment decreases, creating a need to reduce optical axis misalignment. Optical axis misalignment (the misalignment between the first optical axis 6a of the first imaging module 5a and the second optical axis 6b of the second imaging module 5b) can occur due to thermal deformation caused by external heat such as sunlight, or by differences in the amount of expansion of individual components due to temperature increases caused by heat generated by electrical components housed inside the housing 101.

[0031] The effect of suppressing optical axis misalignment according to this embodiment will be described below with reference to a comparative example of this embodiment. Fig. 4 is a perspective view of an image pickup device 900 according to the comparative example of this embodiment, and Fig. 5 is a schematic plan cross-sectional view of the image pickup device 900 according to the comparative example of this embodiment. As shown in Figs. 4 and 5, the image pickup device 900 according to the comparative example has the same structure as the image pickup device 100 according to this embodiment, except for the position of the second rear fixed part.

[0032] In the imaging device 900 according to the comparative example, four fixing parts that fix the circuit board 907 to the housing 901 are arranged symmetrically. The first rear fixing part 181 and the second rear fixing part 982 are arranged symmetrically with respect to the center line 9. The first front fixing part 183 and the second front fixing part 184 are arranged symmetrically with respect to the center line 9.

[0033] When the temperature of the imaging device 900 rises, the housing 901 undergoes thermal deformation due to the difference in the amount of thermal expansion between the circuit board 907 and the housing 901. Thermal deformation of the housing 901 will be described in detail below. The linear expansion coefficient of the housing 901 is greater than that of the circuit board 907. Therefore, when the housing 901 and the circuit board 907 expand due to a rise in temperature, forces F1, F2, F3, and F4 are applied to the housing 901 from the fixing portions 181, 982, 183, and 184 toward the center line 9. The forces F1, F2, F3, and F4 acting on the housing 901 cause the housing 901 to deform.

[0034] Similar to the present embodiment, the housing 901 is formed with a component storage section 115. The component storage section 115 forms a space for accommodating an electrical connector 114, which is a relatively large electrical component. The component storage section 115 is formed to the right of the center line 9, but not to the left. In other words, the housing 901 has an asymmetrical shape due to the component storage section 115. When the housing 901 is formed with a symmetrical shape, thermal deformation also occurs symmetrically. In contrast, in the comparative example, the rigidity of the housing 901 near the component storage section 115 differs from that of the symmetrical configuration. Therefore, in the comparative example, as shown in, for example, FIGS. 6 and 7 , thermal deformation progresses mainly near the left wall surface 15L (see FIG. 15 ) of the component storage section 115 when the temperature rises.

[0035] Fig. 6 is a perspective view of the imaging device 900 according to the comparative example after deformation, and Fig. 7 is a diagram illustrating thermal deformation in various directions of the imaging device 900 according to the comparative example. In Fig. 7, (a) schematically shows the imaging device 900 after deformation as seen from above, (b) schematically shows the imaging device 900 after deformation as seen from behind, and (c) schematically shows the imaging device 900 after deformation as seen from the right.

[0036] 6 , in the comparative example, when the temperature of the imaging device 900 rises, the housing 901 deforms so as to bend about a deformation central axis 909 that passes through the rear end of the left side wall surface 15L of the component storage section 115 and the intersection of the center line 9 of the imaging device 900 and the front end of the imaging device 900. In other words, asymmetric thermal deformation occurs in the housing 901.

[0037] As shown in FIG. 7 , the rear portion of the imaging device 900 bends around the center of the component storage section 115, while the front portion of the imaging device 900 bends around the vicinity of the center line 9 of the housing 901. This causes twisting and bending in the housing 901. As a result, the first imaging module 5a and the second imaging module 5b attached to the housing 901 do not displace symmetrically and evenly. This causes differences in the left-right and up-down displacement and orientation (tilt) of the first optical axis 6a and the second optical axis 6b. When such optical axis misalignment occurs, the accuracy of distance measurement by the imaging device 900 decreases.

[0038] As described above, in the comparative example, the housing 901 deforms asymmetrically, which may result in a large measurement error. In contrast, in the present embodiment, the second rear fixing portion 182 is located to the right (toward the center line 9) of the second rear fixing portion 982 in the comparative example (see FIGS. 3 and 5 ). That is, the position of the second rear fixing portion 182 in the present embodiment is closer to the component storage portion 115 than the position of the second rear fixing portion 982 in the comparative example. Therefore, in the present embodiment, when the temperature of the imaging device 100 rises, the rear portion of the housing 101 deforms symmetrically about the center line 9. That is, the front and rear portions of the housing 101 deform in a balanced manner symmetrically about the center line 9. As a result, in the present embodiment, optical axis misalignment is suppressed.

[0039] Fig. 8 is a diagram showing the relationship between the relative displacement of the first optical axis 6a and the second optical axis 6b when a predetermined temperature change occurs and the distance B from the center line 9 of the housing 101 to the second rear fixed part 182. In Fig. 8, the horizontal axis represents the distance B from the center line 9 to the second rear fixed part 182. The vertical axis represents the relative displacement, which is the difference between the displacement of the first optical axis 6a and the displacement of the second optical axis 6b caused by thermal deformation of the housing 101 due to temperature change.

[0040] As shown in FIG. 8 , in the range of distance B1 or more and distance A or less, the shorter the distance B, the smaller the relative displacement. When distance B is distance B1, the relative displacement is 0 (zero). In the range of distance 0 or more and distance B1 or less, the shorter the distance B, the larger the relative displacement (absolute value). The relationship shown in FIG. 8 is obtained in advance through experiments, etc. As an example, the relative displacement shown in FIG. 8 corresponds to the difference between the angular displacement of the first optical axis 6 a in the yz plane (i.e., the amount of change in angle around the x-axis) and the angular displacement of the second optical axis 6 b in the yz plane (i.e., the amount of change in angle around the x-axis), i.e., the angle between the first optical axis 6 a and the second optical axis 6 b in the yz plane.

[0041] 8, when distance B is a predetermined value B1 that is smaller than distance A and larger than 0, the relative displacement becomes a minimum value (e.g., 0). Thus, there is an optimum value (predetermined value B1) for distance B that is highly effective in reducing optical axis misalignment. For this reason, it is preferable to determine the optimum value (predetermined value B1) in advance through experiments or the like and reflect it in the design of the actual product.

[0042] In this embodiment, as described above, the component storage unit 115 is provided at the rear of the imaging device 100. The component storage unit 115 is provided at a position offset to the right from the center line 9. A first rear fixing portion 181 that fixes the rear of the circuit board 107 to the housing 101 is provided in the offset direction (rightward) of the component storage unit 115 relative to the component storage unit 115. A second rear fixing portion 182 that fixes the rear of the circuit board 107 to the housing 101 is provided in the opposite direction (leftward) to the offset direction of the component storage unit 115 relative to the component storage unit 115. The second rear fixing portion 182 is disposed so that the distance B between the second rear fixing portion 182 and the center line 9 of the housing 101 is shorter than the distance A between the first rear fixing portion 181 and the center line 9 of the housing 101 (distance B<distance A). This arrangement allows the housing 101 to deform symmetrically about the center line 9 when the temperature of the imaging device 100 increases. That is, with the above arrangement, the central axis of deformation of the housing 101 can be brought closer to the center line 9. This balances the displacements of the first imaging module 5a and the second imaging module 5b.

[0043] In this manner, in this embodiment, the amount of change of the first optical axis 6a and the amount of change of the second optical axis 6b are made to generally coincide with each other in response to disturbances such as temperature changes, thereby reducing optical axis misalignment. In particular, the effect of reducing optical axis misalignment in the up-down direction (y direction) of the imaging device 100 is significant. As a result, the accuracy of measurements such as the distance from the imaging device 100 to an object imaged by the imaging device 100 is improved, making it possible to provide a highly reliable imaging device 100.

[0044] Furthermore, according to this embodiment, there is no need to provide a complex holding structure such as a spring cylinder or air cylinder as described in Patent Document 1. By attaching the circuit board 107 to the housing 101 via a rubber washer or the like, there is no need to absorb the difference in thermal expansion between the circuit board 107 and the housing 101. In other words, according to this embodiment, there is no need for a complex holding structure or additional parts such as a rubber washer. This makes it possible to reduce the risk of failure and costs of the imaging device 100.

[0045] Furthermore, according to this embodiment, any shape can be adopted without considering the symmetry of the housing 101, and it is possible to arrange components in a manner suitable for miniaturizing the imaging device 100. In other words, it is possible to provide a compact imaging device 100.

[0046] According to the above-described embodiment, the following advantageous effects are achieved.

[0047] The imaging device 100 includes imaging elements 2a and 2b, a housing 101 that holds the imaging elements 2a and 2b, a circuit board (member) 107 that has a different linear expansion coefficient from the housing 101 and is arranged along the longitudinal direction of the housing 101, and multiple fixing portions 180 that fix the circuit board 107 to the housing 101. The housing 101 has a component storage section 115 that forms a space for storing an electrical connector (electrical component) 114. The component storage section 115 is located at a position offset in the longitudinal direction (x-axis direction) of the housing 101 from a center line 9 of the housing 101 that extends along the lateral direction (z-axis direction) of the housing 101, passing through the center of the housing 101, with the imaging direction of the imaging elements 2a and 2b facing forward. Due to the inclusion of the component storage section 115, the housing 101 is formed to have an asymmetric shape with respect to the center line 9. The multiple fixing portions 180 include a first rear fixing portion 181 and a second rear fixing portion 182 that fix the rear side of the circuit board 107 to the housing 101. The component storage portion 115 is disposed between the first rear fixing portion 181 and the second rear fixing portion 182. The first rear fixing portion 181 is disposed in an offset direction of the component storage portion 115 (to the right (-x direction) in the example shown in FIG. 3 ) relative to the component storage portion 115. The second rear fixing portion 182 is disposed in a direction opposite to the offset direction of the component storage portion 115 (to the left (+x direction) in the example shown in FIG. 3 ). A distance B from the center line 9 to the second rear fixing portion 182 is shorter than a distance A from the center line 9 to the first rear fixing portion 181. This configuration makes it possible to provide an imaging device 100 that has a low risk of failure and low cost and is capable of reducing optical axis misalignment.

[0048] Second Embodiment An imaging device 200 according to a second embodiment of the present invention will be described with reference to Fig. 9. Components that are the same as or equivalent to those described in the first embodiment are given the same reference symbols, and differences will be mainly described. Fig. 9 is a diagram similar to Fig. 3 and is a schematic plan cross-sectional view of the imaging device 200 according to the second embodiment.

[0049] 9 , in the second embodiment, the first rear fixing portion 181 and the second rear fixing portion 182 are arranged so that the distances C to a line that passes through a predetermined position (predetermined point) P in the component storage portion 115 and is parallel to the center line 9 are equal. In other words, the first rear fixing portion 181 and the second rear fixing portion 182 are arranged at positions that are symmetrical with respect to the predetermined position P in the component storage portion 115. That is, the fixing portion 180 of the imaging device 200 according to the second embodiment is arranged so as to satisfy the following two arrangement conditions. (Arrangement Condition 1) The distance B in the x-axis direction from the second rear fixing portion 182 to the center line 9 is shorter than the distance A in the x-axis direction from the first rear fixing portion 181 to the center line 9. (Arrangement Condition 2A) The distance C in the x-axis direction from the first rear fixing portion 181 to the predetermined position P in the component storage portion 115 is equal to the distance C in the x-axis direction from the second rear fixing portion 182 to the predetermined position P.

[0050] In this embodiment, the distance B is set to an optimum value (predetermined value) B1 at which the effect of the optical axis misalignment is greatest. The predetermined position P corresponds to the rear end of the left wall surface 15L of the component storage section 115, which is the starting point of deformation in the comparative example (see FIG. 7).

[0051] As described above, in the second embodiment, the first rear fixing portion 181 and the second rear fixing portion 182 are disposed so that the distances to the line L that passes through the component storage portion 115 and is parallel to the center line 9 of the housing 101 are equal. According to the second embodiment, the same effects as those of the first embodiment can be obtained. Furthermore, according to the second embodiment, the optical axis deviation can be reduced compared to when the second rear fixing portion 182 is positioned further to the left than in the example shown in FIG. 9 .

[0052] Third Embodiment An imaging device 300 according to a third embodiment of the present invention will be described with reference to Fig. 10. Components that are the same as or equivalent to those described in the first embodiment are given the same reference symbols, and differences will be mainly described. Fig. 10 is a diagram similar to Fig. 3 and is a schematic plan cross-sectional view of the imaging device 300 according to the third embodiment.

[0053] 10 , in the third embodiment, the multiple fixing portions 180 are arranged so that the distance E between the first rear fixing portion 181 and the second rear fixing portion 182 is shorter than the distance D between the first front fixing portion 183 and the second front fixing portion 184 (distance E < distance D). That is, the fixing portions 180 of the imaging device 300 according to the third embodiment are arranged so as to satisfy the following two arrangement conditions. (Arrangement Condition 1) The distance B in the x-axis direction from the second rear fixing portion 182 to the center line 9 is shorter than the distance A in the x-axis direction from the first rear fixing portion 181 to the center line 9. (Arrangement Condition 2B) The distance E in the x-axis direction from the first rear fixing portion 181 to the second rear fixing portion 182 is shorter than the distance D in the x-axis direction from the first front fixing portion 183 to the second front fixing portion 184.

[0054] As described above, the imaging device 300 is formed in a box shape with an open rear surface of the housing 101 so that components such as the imaging module 5 and the circuit board 107 can be attached to the housing 101. The rear surface (open surface) of the housing 101 is closed by a rear cover after the components are attached to the housing 101. The thickness of the rear cover is thinner than the front panel of the housing 101. Therefore, the rear cover has lower rigidity than the front panel of the housing 101.

[0055] Because the rear side of the housing 101 is open, the rigidity of the rear side is lower than that of the front side. Therefore, in the comparative example described above (see FIG. 7 ), when a temperature change occurs and substantially equal forces act on the housing 101 from each fixing portion 180, thermal deformation occurs (see FIG. 7( a) ) in which the rectangular housing 101 in the xz plane becomes convex toward the front. As a result, an optical axis misalignment occurs in the x-axis direction.

[0056] In contrast, in the third embodiment, the distance E between the rear fixed portions 181 and 182 adjacent to each other in the left-right direction is shorter than the distance D between the front fixed portions 183 and 184 adjacent to each other in the left-right direction. The force generated by the difference in thermal expansion increases as the distance between the fixed portions increases. Therefore, the forces (inward forces) F1 and F2 applied from the rear fixed portions 181 and 182 toward the center line 9 at the rear of the housing 101 are smaller than the forces (inward forces) F3 and F4 applied from the front fixed portions 183 and 184 toward the center line 9 at the front of the housing 101. This prevents the housing 101 from deforming into a forwardly convex shape, as shown in FIG. 7A . As a result, the effect of reducing the optical axis misalignment of the imaging device 100, mainly in the left-right direction (x-axis direction), can be enhanced.

[0057] As described above, the imaging device 300 according to the third embodiment includes, as the multiple fixing portions 180, multiple front fixing portions 183, 184 that fix the front side of the circuit board (member) 107 to the housing 101, and multiple rear fixing portions 181, 182 that fix the rear side of the circuit board (member) 107 to the housing 101. The distance E between the first rear fixing portion 181 and the second rear fixing portion 182 that are adjacent in the x-axis direction is shorter than the distance D between the front fixing portions 183, 184 that are adjacent in the x-axis direction. This configuration achieves the same effects as the first embodiment. Furthermore, according to the third embodiment, the effect of reducing optical axis misalignment in the left-right direction (x-axis direction) of the imaging device 100 can be further enhanced.

[0058] (Variation of the Third Embodiment) When three or more front fixing parts are provided, the distance E between the first rear fixing part 181 and the second rear fixing part 182 only needs to be shorter than the maximum distance Dmax between adjacent front fixing parts in the x-axis direction. Furthermore, when three or more rear fixing parts are provided in addition to the front fixing parts, the maximum distance Emax between adjacent rear fixing parts in the x-axis direction only needs to be shorter than the maximum distance Dmax between adjacent front fixing parts in the x-axis direction.

[0059] (Fourth Embodiment) An imaging device 400 according to a fourth embodiment of the present invention will be described with reference to Fig. 11. Note that components that are the same as or equivalent to those described in the first embodiment are given the same reference symbols, and differences will be mainly described. Fig. 11 is a diagram similar to Fig. 3, and is a schematic plan cross-sectional view of the imaging device 400 according to the fourth embodiment. Note that the component storage section 115 is not shown in Fig. 11.

[0060] 11 , a notch 407a is provided in the rear portion of the circuit board 407. The notch 407a is provided between the first rear fixing portion 181 and the second rear fixing portion 182, on a line connecting the centers of the first rear fixing portion 181 and the second rear fixing portion 182. The notch 407a is a recessed opening recessed forward from the rear end edge of the circuit board 407. The notch 407a is provided on the center line 9 of the housing 101, and is formed symmetrically with respect to the center line 9.

[0061] In the fourth embodiment, when the temperature rises, deformation of the circuit board 407 progresses around the notch 407a of the circuit board 407, causing the rear portion of the circuit board 407 to expand more than the front portion. In other words, the amount of expansion of the rear portion of the circuit board 407 can be made closer to the amount of expansion of the rear portion of the housing 101. As a result, the force applied to the housing 101 from the circuit board 407 is smaller at the rear portion than at the front portion. In a box-shaped housing 101 with an open rear surface, the force acting on the rear portion of the housing 101 can be reduced, and therefore, similar to the third embodiment, the effect of reducing optical axis misalignment in the left-right direction (x-axis direction) of the image pickup device 100 can be enhanced.

[0062] According to the fourth embodiment, the same effects as those of the first embodiment are achieved. Furthermore, the imaging device 400 according to the fourth embodiment has a notch (opening) 407a provided between the first rear-side fixing portion 181 and the second rear-side fixing portion 182 in the circuit board (member) 407. Therefore, similar to the third embodiment, it is possible to enhance the effect of reducing optical axis misalignment in the left-right direction (x-axis direction) of the imaging device 100.

[0063] (Variation of the Fourth Embodiment) The position of the notch 407a is not limited to being provided on the center line 9. The notch 407a may be provided at a position away from the center line 9. It is sufficient that the notch 407a is provided at least between the first rear fixing part 181 and the second rear fixing part 182. Furthermore, two or more notches 407a may be provided.

[0064] Fifth Embodiment An imaging device 500 according to a fifth embodiment of the present invention will be described with reference to FIG. 12. Note that components that are the same as or equivalent to those described in the first embodiment will be assigned the same reference symbols, and differences will be mainly described. FIG. 12 is a schematic rear cross-sectional view of a fixed unit 180 of an imaging device 500 according to the fifth embodiment. The multiple fixed units 180 have the same configuration. For this reason, the configuration of the fixed unit 180 will be described using the first rear fixed unit 181 shown in FIG. 12 as a representative.

[0065] As shown in FIG. 12 , the fixing portion 180 has a boss 585 (hereinafter also referred to as the housing boss) provided on the housing 101, a boss 586 (hereinafter also referred to as the cover boss) provided on the bottom cover 102, and a screw 587. The housing boss 585 protrudes downward from the top plate of the housing 101. The cover boss 586 protrudes upward from the bottom cover 102. The bottom cover 102 is a rectangular plate-shaped cover that covers the bottom surface (open surface) of the housing 101. The bottom cover 102 is disposed opposite the top plate of the housing 101. The bottom cover 102 is disposed along the longitudinal direction of the housing 101.

[0066] The housing boss 585 has a female thread formed therein. The male thread of a screw 587 is screwed into the female thread. The cover boss 586 has a recess (deep counterbore) 586a with an open bottom surface. The head of the screw 587 is housed in the recess 586a. This prevents the screw 587 from protruding from the bottom cover 102.

[0067] The screw 587 is inserted from below through the through-hole of the cover boss 586 and the through-hole of the circuit board 107, and is screwed into the female thread portion of the housing boss 585. As a result, the circuit board 107 is sandwiched in the vertical direction between the housing boss 585 and the cover boss 586. In this embodiment, the circuit board 107 is sandwiched between a pair of bosses (585, 586) in each of the multiple fixing portions 181 to 184. In other words, the first rear fixing portion 181 fixes the circuit board 107 to the housing 101 and the bottom cover 102 at the same location, the second rear fixing portion 182 fixes the circuit board 107 to the housing 101 and the bottom cover 102 at the same location, the first front fixing portion 183 fixes the circuit board 107 to the housing 101 and the bottom cover 102 at the same location, and the second front fixing portion 184 fixes the circuit board 107 to the housing 101 and the bottom cover 102 at the same location.

[0068] The imaging device 900 according to the comparative example (see FIG. 7 ) described above has a two-layer structure in which the housing 101 and the circuit board 107 are fixed by the fixing portion 180. Therefore, thermal deformation caused by the difference in thermal expansion during temperature rise results in an upward convex deformation (bending in the y direction) due to the bimetal effect (see FIG. 7B ). This causes the first imaging module 5a to rotate around the first optical axis 6a (clockwise in FIG. 7B ), while the second imaging module 5b rotates around the second optical axis 6b (counterclockwise in FIG. 7B ). In other words, optical axis misalignment occurs in the rotational direction around the optical axis.

[0069] In contrast, the fifth embodiment has a three-layer structure in which the housing 101, circuit board 107, and bottom cover 102 are fixed at the same location by fixing portions 180, as shown in Fig. 12. The bottom cover 102 is made of the same material as the housing 101. In this configuration, when the temperature rises, thermal deformation of the housing 101 and circuit board 107 (deformation that results in an upward convex shape) is offset by thermal deformation of the bottom cover 102 and circuit board 107 (deformation that results in a downward convex shape). As a result, thermal deformation of the housing 101 when the temperature rises can be reduced, and optical axis misalignment of the imaging module 5 attached to the housing 101 can be reduced.

[0070] The fifth embodiment achieves the same effects as the first embodiment. Furthermore, the circuit board (member) 107 is disposed between the housing 101 and the bottom cover (cover) 102 facing the housing 101. The multiple fixing portions 180 fix the circuit board 107 to the housing 101 and the bottom cover 102 at the same locations. In this configuration, by using a material for the bottom cover 102 that is the same as or has a similar linear expansion coefficient as the material for the housing 101, thermal deformation due to the bimetallic effect between the housing 101 and the circuit board 107 can be offset by thermal deformation due to the bimetallic effect between the bottom cover 102 and the circuit board 107. This effectively suppresses optical axis misalignment, particularly in the rotational direction around the optical axis. Furthermore, the rigidity of the entire imaging device 500 is increased. This suppresses thermal deformation of the imaging device 500 and reduces optical axis misalignment in each direction.

[0071] Modification of Fifth Embodiment The configuration in which the circuit board 107 is sandwiched between the housing boss 585 and the cover boss 586 does not have to be applied to all of the four fixing portions 180 .

[0072] Housing 101 is formed in a box shape with a wall at the front and an open rear face. Therefore, the rigidity of the rear portion of housing 101 is lower than the rigidity of the front portion of housing 101. Therefore, first rear fixing portion 181 and second rear fixing portion 182 may be configured to sandwich circuit board 107 between housing boss 585 and cover boss 586, and first front fixing portion 183 and second front fixing portion 184 (all of the multiple front fixing portions) may be configured to fix circuit board 107 only to housing 101.

[0073] This makes it possible to balance the rigidity between the front and rear of the imaging device 500. As a result, it is possible to effectively reduce the optical axis misalignment of the imaging device 500 in the left-right direction (x-axis direction).

[0074] The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the present invention. For example, the following modifications are also within the scope of the present invention, and it is possible to combine the configuration shown in the modification with the configuration described in the above-described embodiment, to combine the configurations described in the different embodiments, or to combine the configurations described in the following different modifications.

[0075] <Modification 1> In the above embodiment, an example has been described in which all of the component storage sections 115 are arranged to the right of the center line 9. However, the component storage sections 115 may be arranged to straddle the center line 9. In this case, the distance from the center line 9 to the left wall surface 15L of the component storage sections 115 is different from the distance from the center line 9 to the right wall surface 15R of the component storage sections 115, and therefore the housing 101 is formed to have an asymmetric shape.

[0076] <Modification 2> In the above embodiment, an example has been described in which the electrical connector 114 is stored in the component storage section 115 that forms a rectangular parallelepiped space, but the present invention is not limited to this. The component storage section 115 can store various relatively large electrical components, such as capacitors attached to the circuit board 107. Note that the component storage section 115 that stores a cylindrical capacitor may also be configured to form a cylindrical space. For example, the component storage section 115 may be formed in a cylindrical shape.

[0077] <Variation 3> In the above embodiment, a countermeasure against deformation of the housing 101 due to the difference in thermal expansion between the housing 101 and the circuit board 107 fixed to the housing 101 was described as an example. However, the present invention is not limited to this. When the materials of the members fixed to the housing 101 by the multiple fixing portions 180 are different from those of the housing 101, the optical axis misalignment due to the thermal deformation described in the above embodiment occurs. The present invention can be applied to deformation of the housing 101 due to the difference in thermal expansion between the housing 101 and various members fixed to the housing 101. For example, the present invention may be applied when a reinforcing member for reinforcing the housing 101 is attached to the housing 101 and the materials of the reinforcing member are different. When the housing 101 is made of an aluminum-based material and the reinforcing member is made of an iron-based material (e.g., stainless steel), a difference in thermal expansion occurs between the two. Furthermore, the present invention may be applied when a resin member for maintaining the waterproofness (airtightness) of the housing 101 is attached to the housing 101. In the above embodiment, an example was described in which the linear expansion coefficient of the housing 101 is greater than the linear expansion coefficient of the circuit board 107 fixed to the housing 101, but the present invention may also be applied to cases in which the relationship between the linear expansion coefficients is reversed.

[0078] <Modification 4> In the above embodiment, an example has been described in which the imaging device 100 is a stereo camera equipped with two imaging elements 2 a and 2 b. However, imaging devices to which the present invention can be applied are not limited to this. The present invention may also be applied to an imaging device that has three or more imaging elements 2 and measures distance by selecting multiple imaging elements 2. The present invention may also be applied to an imaging device that has a single imaging element 2. In this case, a distance measurement system is configured by multiple imaging elements and a processing device that processes image signals from the multiple imaging elements.

[0079] <Modification 5> As an example of a combination of the configurations described in the different embodiments above, a plurality of fixing portions 180 may be arranged so as to satisfy all of (Arrangement Condition 1), (Arrangement Condition 2A), and (Arrangement Condition 2B) described in the first to third embodiments. Furthermore, the notch (opening) 407a described in the fourth embodiment may be provided on the circuit board, or the fixing structure described in the fifth embodiment may be adopted.

[0080] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. The present invention is not limited to those having all of the configurations described in the above embodiments, and also includes those in which some of the configurations are omitted.

[0081] 2...imaging element, 2a...first imaging element, 2b...second imaging element, 3...imaging board, 3a...first imaging board, 3b...second imaging board, 4a...first lens, 4b...second lens, 5...imaging module, 5a...first imaging module, 5b...second imaging module, 6a...first optical axis, 6b...second optical axis, 9...center line of housing, 100...imaging device, 101...housing, 102...bottom cover (cover), 1 07...circuit board (member), 114...electrical connector (electrical component), 115...component storage section, 180...fixing section, 181...first rear side fixing section, 182...second rear side fixing section, 183...first front side fixing section, 184...second front side fixing section, 200, 300, 400...imaging device, 407...circuit board (member), 407a...notch (opening), 500...imaging device, 585...casing boss, 586...cover boss

Claims

1. An imaging device, comprising: an imaging element; a housing that holds the imaging element; a member having a coefficient of linear expansion different from that of the housing and disposed along the longitudinal direction of the housing; and a plurality of fixing portions that fix the member to the housing, wherein the housing has a component storage portion that forms a space for storing electrical components, the component storage portion is provided at a position offset in the longitudinal direction of the housing with respect to a center line of the housing that extends along the short-side direction of the housing passing through the center of the housing with the imaging direction of the imaging element being forward, the housing is formed in an asymmetric shape with respect to left and right with reference to the center line by having the component storage portion, the plurality of fixing portions include a first rear-side fixing portion and a second rear-side fixing portion that fix the rear side of the member to the housing, the component storage portion is disposed between the first rear-side fixing portion and the second rear-side fixing portion, the first rear-side fixing portion is disposed in the offset direction of the component storage portion with reference to the component storage portion, the second rear-side fixing portion is disposed in a direction opposite to the offset direction of the component storage portion with reference to the component storage portion, and a distance from the center line to the second rear-side fixing portion is shorter than a distance from the center line to the first rear-side fixing portion.

2. The imaging device according to claim 1, wherein the first rear-side fixing portion and the second rear-side fixing portion are disposed such that distances to a line passing through the component storage portion and parallel to the center line are equal.

3. The imaging device according to claim 1, wherein the housing is formed in a box shape with an open rear surface, the plurality of fixing portions include a plurality of front-side fixing portions that fix the front side of the member to the housing, and a distance between the first rear-side fixing portion and the second rear-side fixing portion is shorter than a distance between adjacent front-side fixing portions.

4. The imaging device according to claim 1, wherein the housing is formed in a box shape with an open rear surface, and an opening is provided between the first rear-side fixing portion and the second rear-side fixing portion in the member.

5. The imaging device according to claim 1, wherein the member is disposed between the housing and a cover facing the housing, and the first rear-side fixing portion and the second rear-side fixing portion fix the member to the housing and the cover at the same location, respectively.

Images