Stereo camera device

Abstract

To provide a stereo camera device having improved weatherability.SOLUTION: A stereo camera device has: a plurality of cameras; an electronic circuit that calculates the distance to an object based on image data captured by the plurality of cameras; and a housing case that accommodates the plurality of cameras and the electronic circuit. The housing case is formed of a first case member and a second case member. The plurality of cameras are arranged in the first case member. The electronic circuit is arranged in the second case member.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a stereo camera device. [Background technology]

[0002] In recent years, in the field of automobiles as well as in the field of industrial machinery such as forklifts and hydraulic excavators, various safety devices have been installed on vehicles to avoid accidents caused by carelessness of the driver. As one of the safety measures, the installation of external recognition sensors that detect surrounding objects is being promoted. External recognition sensors include stereo cameras and millimeter wave radars. By using such safety devices, when objects or workers around the vehicle are detected, the driver's attention is alerted and the vehicle's driving is controlled according to the detected surrounding conditions, thereby avoiding accidents associated with vehicle collisions.

[0003] A stereo camera calculates distance using parallax information from images obtained by two cameras. Therefore, although the detection distance is shorter than that of a monocular camera, it can detect objects at close range with high accuracy. Distance measurement using a stereo camera is, in principle, premised on the optical axes of the two cameras being parallel. When mounting a stereo camera on a vehicle, it is difficult to maintain a strict parallel arrangement due to changes in lens position over time caused by temperature or vibration, mechanical tolerances of the housing, etc.

[0004] A stereo camera has been proposed that includes a camera stay that is arranged in parallel with a pair of monocular cameras and is integrally connected to each other at a position where the optical axes of the monocular cameras are aligned on the same straight line, an image correction means that corrects the images captured by each monocular camera, and a distance calculation means that calculates the parallax from the corrected images corrected by the image correction means and calculates the distance to the subject (see, for example, Patent Document 1). A method has been proposed in which a calibration target is installed in front of the stereo camera and a laser range finder is installed behind it, and the parameters of the stereo camera are calibrated using the distance L1 from the laser range finder to the reference surface of the camera stay and the distance L2 from the laser range finder to the calibration target (see, for example, Patent Document 2). A technology has been proposed in which the lens position shift is estimated from the state of image distortion captured by the stereo camera, and the image is electronically transformed by image correction processing to correct the distortion and reproduce the original image (see, for example, Patent Document 3). Summary of the Invention [Problem to be solved by the invention]

[0005] The wider the angle of the camera, the more complex the image distortion that occurs and the greater the amount of correction required. It is difficult to achieve sufficient distortion correction using only geometric correction using polynomial approximation, so a mechanical structure that can stably maintain the position between the cameras is required. In environments subject to temperature and weather changes, such as construction sites, a weather-resistant structure that includes waterproofing and dustproofing is desirable.

[0006] An object of one aspect of the present invention is to provide a stereo camera device with improved weather resistance. [Means for solving the problem]

[0007] In one aspect, a stereo camera device has a plurality of cameras, an electronic circuit that calculates a distance to the object based on image data captured by the plurality of cameras, and a housing case that accommodates the plurality of cameras and the electronic circuit, the housing case being formed of a first case member and a second case member, the plurality of cameras being disposed in the first case member, and the electronic circuit being disposed in the second case member. Effect of the Invention

[0008] A stereo camera device with improved weather resistance is realized. [Brief description of the drawings]

[0009] [Figure 1] 1 is an external view of a stereo camera device according to an embodiment; [Figure 2A] FIG. 2 is a hardware configuration diagram of the stereo camera device of FIG. [Figure 2B] FIG. 2B is a functional block diagram of the integrated circuit of FIG. 2A. [Diagram 3] 1A and 1B are diagrams illustrating the principle of distance measurement by a stereo camera device. [Figure 4] 11 is a flowchart of calibration of the stereo camera device. [Diagram 5] FIG. 13 is a diagram showing the positional relationship of devices during calibration. [Figure 6] FIG. [Figure 7] FIG. 2 is an exploded perspective view of the stereo camera device. [Figure 8A] FIG. 2 is a vertical sectional view of the stereo camera device. [Figure 8B] FIG. 2 is a horizontal cross-sectional view of the stereo camera device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Fig. 1 is an external view of a stereo camera device 100 according to an embodiment, and Fig. 2A is a hardware configuration diagram of the stereo camera device 100. As shown in Figs. 1 and 2A, the stereo camera device 100 has cameras 10A and 10B, a distance measurement sensor 20, an electronic circuit 50, and a housing case 101 that houses these optical devices and the electronic circuit 50. The housing case 101 is an example of a case. In this example, two cameras 10A and 10B are used, but distance measurement may be performed using three or more cameras.

[0011] In FIG. 1, the arrangement direction of the cameras 10A and 10B is the X direction, the optical axis direction is the Z direction, and the direction perpendicular to the X direction and the Z direction is the Y direction. As described later, the cameras 10A and 10B and the distance measuring sensor 20 are held in a predetermined positional relationship inside the housing case 101 by the holding member 30 (see FIGS. 7, 8A, and 8B). The housing case 101 functions as a protective member for these optical devices and the electronic circuit 50. By disposing the cameras 10A and 10B and the distance measuring sensor 20 inside the housing case 101, robustness against collision objects, dustproofness against dust and dirt, waterproofness against rain, etc. are ensured. The housing case 101 does not need to be completely sealed as long as it can protect the optical devices, electronic circuits, etc. inside. In one embodiment, the cameras 10A and 10B and the distance measuring sensor 20 are integrally held in a certain positional relationship by the holding member 30 inside the housing case 101, and positional accuracy is maintained.

[0012] Housing case 101 is, for example, a metal or alloy case formed by die casting. In the example of Fig. 1, housing case 101 is made by aluminum die casting. Housing case 101 is formed of upper case 15 and lower case 40 that can be separated diagonally with respect to the bottom surface, and the parts accommodated inside housing case 101 can be easily maintained, repaired, replaced, etc.

[0013] The housing case 101 has camera openings 16A and 16B that enable imaging by the cameras 10A and 10B, and a distance measurement opening 17 for distance measurement by the distance measurement sensor 20. The housing case 101 has a cover glass 102 as a light-transmitting member at its front surface. The cover glass 102 closes the camera openings 16A and 16B and the distance measurement opening 17, maintaining light transmittance and keeping the housing case 101 airtight. The cover glass 102 is preferably a single sheet of glass, and prevents optical errors caused by differences in thickness or warping between the camera openings 16A and 16B and the distance measurement opening 17.

[0014] The electronic circuit 50 performs image processing, distance calculation processing, and the like based on image data (captured images) of the measurement object photographed by the cameras 10A and 10B, and measures the distance to the measurement object.

[0015] On the other hand, the distance measuring sensor 20 measures the distance to the measurement object by receiving the reflected light of the light irradiated on the measurement object in order to calibrate the image distance measurement. The distance measuring sensor 20 is, for example, a ToF sensor that measures the distance to the measurement object based on the time of flight (TOF) from when the measurement object is irradiated with light (electromagnetic wave) to when the reflected light from the measurement object is received.

[0016] 2B is a functional block diagram of the electronic circuit 50. The electronic circuit 50 may be a microprocessor configured with a large-scale integrated circuit (LSIC) or may be a logic device such as a field programmable gate array (FPGA). The electronic circuit 50 functions as a control unit 50A, and has an image processing unit 51, a parallax calculation unit 52, a calibration calculation unit 53, a distance calculation unit 54, and a data input unit 55 as its functions.

[0017] The data input unit 55 receives the captured images output from the cameras 10A and 10B, and the distance information output from the distance measuring sensor 20. The captured images are input from the data input unit 55 to the image processing unit 51. The distance information is input from the data input unit 55 to the calibration calculation unit 53.

[0018] The image processing unit 51 performs appropriate image processing on the captured image to generate a corrected image, and supplies the corrected image to the parallax calculation unit 52. The parallax calculation unit 52 calculates the parallax p between the cameras 10A and 10B from the corrected image by a pattern matching method or the like. The parallax p is input to the distance calculation unit 54 and the calibration calculation unit 53.

[0019] The calibration calculation unit 53 calculates the distance Z from the optical centers of the cameras 10A and 100B to the measurement object based on the distance information L to the measurement object obtained by the distance measurement sensor 20 and the known positional relationship between the distance measurement sensor 20 and the cameras 10A and 10B. The calibration calculation unit 53 uses the calculated distance Z and the parallax p input from the parallax calculation unit 52 to obtain a B*f value and a parallax offset Δp, and supplies the B*f value and Δp to the distance calculation unit 54. Here, the B*f value is the product of the distance (baseline length) B between the actual optical axes of the cameras 10A and 10B and the actual focal length f, as described later.

[0020] The distance calculation unit calculates the distance Z to the measurement object using the parallax p input from the parallax calculation unit 52, and the parallax offset Δp and B*f value input from the calibration calculation unit 53, as follows: Z = B × f / (p + Δp) (1) and calculate.

[0021] The calibration of the stereo camera device 100 may be performed during product inspection of the stereo camera device 100 before it is shipped from a factory, or may be performed using a measurement target when the stereo camera device 100 is used after being installed on a moving body or the like.

[0022] <Principle of distance measurement> 3 is a diagram for explaining the principle of distance measurement by the stereo camera device 100. The cameras 10A and 10B are installed at a distance B apart. The distance B is the distance between the optical axes of the cameras 10A and 10B, and is also called the baseline. The focal lengths of the cameras 10A and 10B are f, and their optical centers are O. A , and O B , each imaging plane is s A , and s B What is desired to be found is the distance Z from the optical center of cameras 10A and 10B to the measurement object A.

[0023] The image of the object A, which is located at a distance Z in the optical axis direction (Z direction) from the optical center OA of the camera 10A, is formed by a straight line AO A and the imaging surface s A P, which is the intersection point with A On the other hand, the camera 10B captures the same object A on the imaging plane s B Upper position P B Here, a straight line AO ​​passes through the optical center OB of the camera 10B. A A straight line PL parallel to the image plane s B The intersection point with P A '. P A ' and P B The distance between is the parallax p between cameras 10A and 10B.

[0024] point P A ' is the image point P with respect to the optical axis of the camera 10A A The disparity p represents the position of P A ' and P B and corresponds to the amount of positional deviation on the images of the same measurement object A captured by the two cameras 10A and 10B.

[0025] triangle AO A -O B and triangle O B -P A '-P B are similar, so Z = B × f / p (2) If the distance (baseline length) B between the optical axes of cameras 10A and 10B and the focal point f are known, the distance Z can be found from the parallax p. However, in reality, the base line length B, focal length f, and parallax p change slightly due to fluctuations over time in the lens optical axis caused by temperature changes, vibrations, and other factors. Therefore, Z is found from equation (1) using the parallax offset Δp as described above. Z = B × f / (p + Δp) (1) By measuring the distance Z to the object A to be measured at multiple positions using equation (1), the actual values ​​of B and f can be found using simultaneous equations.

[0026] <Proofreading process> FIG. 4 is a flowchart of the calibration, and FIG. 5 is a diagram showing the positional relationship of the devices during calibration. In inspection before shipment from the factory, calibration may be performed using a calibration target T. In actual distance measurement, calibration may be performed using a measurement target as described above. In FIG. 5, the distance measurement sensor 20 is drawn behind (on the -Z side) of the cameras 10A and 10B to explain the calibration process, but the distance measurement sensor 20 may be held integrally with the cameras 10A and 10B by a holding member 30.

[0027] 5, a calibration target T is placed in front of the stereo camera device 100 in the measurement direction (Z direction) (S1). Next, the stereo camera device 100 is placed at a predetermined position so that the light beam emitted from the distance measurement sensor 20 irradiates the feature point T1 of the calibration target T (S2).

[0028] The distance measurement sensor 20 has a light source that irradiates a light beam onto the calibration target T, and a photodetector that detects reflected light from the calibration target T. The light source is, for example, a laser diode, and the photodetector is, for example, a photodiode. The optical axes of the light source and the photodetector are aligned in the same direction. The photodetector detects that the optical axes of the emitted light and the reflected light are aligned in the same direction. The distance measurement sensor 20 measures the time ToF from when the light beam is emitted from the light source to when the reflected light is received, and measures the distance L1 to the calibration target T based on the measured time (S3). The distance calculation unit 54 of the control unit 50A calculates the distance Z between the optical center O of the camera and the calibration target T from the measured distance L1 measured by the distance measurement sensor 20 and the known value ΔZ (S4). The known value ΔZ is the distance between the distance measurement origin of the distance measurement sensor 20 and the optical center O of the cameras 10A and 10B, but the optical center O of the cameras 10A and 10B attached to the same holding member 30 and the distance measurement origin of the distance measurement sensor 20 are in approximately the same plane, so ΔZ can be considered to be zero. If there is a difference in the Z direction between the optical center O of the cameras 10A and 10B and the distance measurement limit of the distance measurement sensor 20 when attached to the holding member 30, the distance Z is calculated using ΔZ.

[0029] On the other hand, the cameras 10A and 10B capture images of the feature points T1 of the calibration target T (S5). The captured images of the feature points T1 are processed by the image processing unit 51 to generate corrected image data (corrected image) (S6). The parallax calculation unit 52 calculates the parallax p with respect to the calibration target T from the generated corrected image (S7). The position of the calibration target T in the Z direction is changed and steps S1 to S7 are repeated two or more times (YES in S8).

[0030] The calibration calculation unit 53 calculates the actual B*f value and the parallax offset Δp using two or more pairs of the distance Z and the parallax p. The B*f value and the parallax offset Δp are data for calibration.

[0031] When the stereo camera device 100 is attached to a vehicle and used at a work site, the stereo camera device 100 detects obstacles and workers in front, on the sides, and behind. If there is a risk of collision based on the relative speed, relative position, etc. between the obstacle or worker and the vehicle, an alert may be issued or automatic braking may be activated. If the distance measurement accuracy is low, the automatic braking may be activated frequently, which may interfere with work, so it is desirable to activate the automatic braking only when the risk of contact with a person is high. To achieve this, a resolution capable of distinguishing between workers and materials, etc. is required. In addition, it is necessary to maintain distance measurement performance even in outdoor environments with large temperature differences and the presence of dust and raindrops.

[0032] In the embodiment, the cameras 10A and 10B and the distance measurement sensor 20 are held by a holding member 30 separate from the housing case 101 using a mechanical structure described below, thereby maintaining as high a positional accuracy as possible between the cameras 10A and 10B and the distance measurement sensor 20. Even if the positional relationship of the optical devices changes over time due to temperature differences, vibrations, etc., the measurement accuracy of the stereo camera device 100 is compensated for by the calibration function described above.

[0033] <Device configuration> FIG. 6 is an exploded perspective view of the camera 10. The cameras 10A and 10B have the same configuration, and therefore will be described as one camera 10. The camera includes a lens 21 and an image sensor 23 mounted on a printed circuit board 25. The lens 21 has a plurality of lens elements inside a lens cell 211. The image sensor 23 is, for example, a CMOS sensor. The lens 21 and the printed circuit board 25 on which the image sensor 23 is mounted are incorporated into an aluminum die-cast base member 22 to constitute the monocular camera 10. The base member 22 is formed with a cylindrical screw hole 24 for receiving the lens 21. The screw hole 24 is formed coaxially with the optical axis of the lens 21 inside a cylinder 223 protruding in the Z direction of the base member 22. The printed circuit board 25 is fixed to the mounting surfaces 221 and 222 of the base member 22 so that the image sensor 23 is coaxial with the optical axis of the lens 21.

[0034] The mounting surface 221 of the base member 22 surrounds the periphery of the image sensor 23, and mounting surfaces 222 are provided at a plurality of locations on the outer side of the mounting surface 221. As described below, the mounting surface 222 is used for temporarily fixing the vicinity of the outer edge of the printed circuit board 25 at a plurality of locations, and the printed circuit board 25 is finally fixed by the mounting surface 221. By providing the mounting surface 222 at a position symmetrical with respect to the central axis of the image sensor 23, it is possible to prevent uneven tensile stress from being generated in the printed circuit board 25 due to the hardening and shrinkage of the adhesive during temporary fixing, and to suppress misalignment.

[0035] Fig. 7 is an exploded perspective view of the stereo camera device 100, Fig. 8A is a vertical cross-sectional view along the YZ plane of Fig. 1, and Fig. 8B is a horizontal cross-sectional view along the XZ plane of Fig. 1. As shown in Figs. 7 and 8B, the cameras 10A and 10B and the distance measuring sensor 20 are attached to the holding member 30. As described with reference to Fig. 6, the lens 21A of the camera 10A is fitted into the screw hole 24A of the base member 22A, and the optical axis of the lens 21A is aligned with the optical axis of the image sensor 23A mounted on the printed circuit board 25A. The cylinder 223 of the base member 22A is inserted into the fitting hole 13A of the holding member 30 and positioned.

[0036] Similarly, lens 21B of camera 10B is fitted into screw hole 24B of base member 22B, and the optical axis of lens 21B is aligned with the optical axis of image sensor 23B mounted on printed circuit board 25B. Cylinder 223 (see FIG. 6) of base member 22B is inserted into fitting hole 13B of holding member 30 and positioned.

[0037] Through the fitting holes 13A and 13B, the cameras 10A and 10B are attached to the holding member 30 so that their optical axes are parallel. In the cameras 10A and 10B, the optical axes of the printed circuit boards 25A and 25B on which the image sensors 23A and 23B are mounted are aligned with the lenses 21A and 21B, respectively, and the tilt angles around the optical axes as the rotation axes are preset. Therefore, even after the cameras 10A and 10B are attached to the holding member 30 so that their optical axes are parallel to each other, the optical arrangements determined in the respective cameras 10 are maintained.

[0038] The distance measurement sensor 20 is mounted on a printed circuit board 31. The distance measurement sensor 20 is disposed approximately halfway between the cameras 10A and 10B so that its light beam entrance / exit window is exposed in the opening 14 of the holding member 30. The distance measurement sensor 20 is attached to the holding member 30 with the optical axes of the light source and the photodetector aligned in the same direction. As a result, the cameras 10A and 10B and the distance measurement sensor 20 are held by the holding member 30 with their respective optical axes appropriately adjusted.

[0039] 8A and 8B, lenses 21A and 21B are each formed by combining a plurality of lens elements. Lenses 21A and 21B are screwed into screw holes 24A and 24B formed in base members 22A and 22B, and are fixed so that the imaging surfaces of image sensors 23A and 23B are substantially flush with each other.

[0040] Lenses 21A and 21B are, for example, retrofocus type lenses combining a plurality of lens elements, and each lens element is accommodated in lens cell 211 with its axis aligned. Lens cell 211 is formed with fitting portion 62 for positioning the optical axis, screwing portion 63 for screwing lens 21 in the optical axis direction with a predetermined axial force, and locking portion 64. Generally, a wide-angle lens such as a retrofocus lens has a short focal length, and as shown in the figure, a principal point position 65 of the optical system is arranged biased toward image sensor 23. Even in such a retrofocus type arrangement, it is desirable that principal point position 65 does not change inside screw hole 24 due to positional deviation or change in attitude of each lens element.

[0041] In this embodiment, the fitting portion 62 is provided at the end of the lens cell 211 closest to the image sensor 23, thereby fixing the lens 21 at least near the principal point position 65 of the optical system and maintaining the parallelism of each lens element with respect to the optical axis.

[0042] The screwing portion 63 that screws into the screw hole 24 is provided closer to the subject (the side farther from the image sensor 23) than the fitting portion 62, and the locking portion 64 is provided even closer to the subject. When the lens 21 screws into the screw hole 24, the locking portion 64 abuts against the base member 22 with a predetermined axial force, and the lens 21 can be positioned with respect to the image sensor 23. Even if there is expansion and contraction due to temperature changes and creep due to aging, an axial force that can withstand vibrations and impacts is maintained.

[0043] Because lenses 21A and 21B are constrained by fitting portions 62A and 62B, for example, when the temperature rises, they move away from image sensors 23A and 23B due to thermal expansion. Meanwhile, principal point position 65 moves closer to image sensor 23 relative to screw-in portion 63. This reduces the variation in the distance between principal point position 65 and image sensor 23, and suppresses changes in imaging characteristics due to temperature changes.

[0044] The printed circuit boards 25A and 25B on which the image sensors 23A and 23B are mounted are aligned with the lenses 21A and 21B fixed to the base members 22A and 22B so that the imaging characteristics are appropriate. In the alignment adjustment, alignment is adjusted for six elements, including the position in the optical axis (Z) direction, the coordinates in the XY plane perpendicular to the optical axis, the tilt component α around the x axis, the tilt component β around the y axis, and the tilt component γ around the z axis. Thereafter, while maintaining the aligned position and posture, an ultraviolet (UV) curing adhesive filled in the gap between the mounting surface 222 (see FIG. 6) formed on the base members 22A and 22B and the printed circuit boards 25A and 25B is irradiated with UV light to be cured.

[0045] By this adhesive curing, the aligned printed circuit boards 25A and 25B are temporarily fixed, and the positions and orientations of the imaging surfaces of the image sensors 23A and 23B relative to the lenses 21A and 21B are maintained.

[0046] On the other hand, a thermosetting adhesive is applied in advance to the mounting surfaces 221 (see FIG. 6) of the base members 22A and 22B, and the cameras 10A and 10B after alignment adjustment are placed in a heating furnace to harden the thermosetting adhesive. This ensures that the adhesive strength between the base members 22A and 22B and the printed circuit boards 25A and 25B is maintained even if the cameras are left in a high-temperature environment simulating a hot sun.

[0047] In the embodiment, the UV-curing adhesive is an adhesive mainly made of acrylic resin or urethane resin, which is relatively resistant to impact and tension and highly flexible. The thermosetting adhesive is an adhesive mainly made of epoxy resin, which is highly heat-resistant, hard, and tough. The two types of mounting surfaces 221 and 222 are provided on the base member 22 to separate the application positions, and the highly flexible UV-curing adhesive is placed on the outside, thereby preventing peeling due to shear stress caused by the difference in thermal expansion coefficient between the base member 22 and the printed circuit board 25.

[0048] It is advisable to select a thermosetting adhesive with a higher intermolecular cohesive force, i.e., Young's modulus (elastic modulus), than or the same as that of the UV-curing adhesive. The UV-curing adhesive and the thermosetting adhesive may have the same base agent. For example, epoxy resin may be used as the base agent, and by selecting the curing accelerator to be mixed in, either the UV-curing type or the thermosetting type may be used depending on the process design requirements.

[0049] Generally, UV-curing adhesives cure with short UV exposure, so they are effective in ensuring takt time in the assembly process, but their heat resistance may be insufficient. Thermosetting adhesives have high heat resistance, but take a long time (one hour or more) to completely cure, making them difficult to incorporate into alignment adjustment processes.

[0050] Therefore, in the embodiment, once the alignment adjustment is completed, the parts are temporarily fixed with a UV-curable adhesive. After that, the process is designed so that multiple adjusted semi-finished products are put into a heating furnace together and a batch process is performed to cure the thermosetting adhesive. This ensures the final adhesive strength even if the mounting surface 222 of the base member 22 is a location where the energy of the UV irradiation light does not easily reach.

[0051] As shown in FIG. 6, mounting surface 221 of base member 22 surrounds image sensor 23, and printed circuit board 25 and mounting surface 221 are sealed with a thermosetting adhesive to prevent dust and water droplets from entering the interior of camera 10.

[0052] In the embodiment, an example was shown in which a UV-curable adhesive and a thermosetting adhesive were used together to shorten the takt time, but the method is not limited to this. For example, a method may be used in which hot air is applied to the thermosetting adhesive for a short time to temporarily cure it to the extent that the alignment adjustment does not shift, and then the adhesive is put into a heating furnace together to completely cure it. The latter method also has little effect on the takt time, so it is not necessary to use a UV-curable adhesive.

[0053] In order to ensure the mechanical strength and reliability of the bond, any type of adhesive can be combined, not limited to UV-curing or heat-curing types, as long as a process for pre-curing can be added in a short time prior to full curing.

[0054] The cameras 10A and 10B are individually aligned and the thermosetting adhesive is allowed to completely harden, after which they are inspected with a single eye and attached to the holding member 30. The cylinders 223 of the base members 22A and 22B, which are formed coaxially with the optical axes of the lenses 21A and 21B, are inserted into the fitting holes 13A and 13B of the holding member 30, and the outer surfaces of the base members 22A and 22B are abutted against the locking portions 29 (see FIG. 7) in the rotational direction, thereby determining the position and attitude around the optical axis.

[0055] In the XY plane perpendicular to the optical axes of the lenses 21A and 21B, the front faces of the base members 22A and 22B are abutted against the abutment surface 30a of the holding member 30, and the cameras 10A and 10B are fixed to the holding member 30 by screw fastening. This abutment surface 30a functions as a positioning means common to the cameras 10A and 10B. During the above-mentioned alignment adjustment, the position of the printed circuit board 25 relative to the base member 22 can also be adjusted based on the abutment surface 30a.

[0056] In the embodiment, cameras 10A, 10B are individually assembled to base members 22A, 22B in advance and then fixed to holding member 30. However, it is also possible to provide screw holes 24 and mounting surfaces 221 and 222 in holding member 30 without using base members 22A, 22B, and to directly assemble lenses 21A, 21B and printed circuit boards 25A, 25B to holding member 30.

[0057] An opening 16 for a camera and an opening 17 for distance measurement are formed on the front surface of the upper case 15 of the housing case 101, and an opening 43 for cable wiring 400 (see FIG. 8A) serving as an external interface is formed on the rear surface of the lower case 40. The upper case 15 and the lower case 40 have a joint surface (or dividing surface) 42 that is inclined obliquely with respect to the XZ plane (see FIG. 1) so that functions are shared between the front and rear sides of the housing case 101. The upper case 15 and the lower case 40 are connected flush with each other at the joint surface 42.

[0058] The upper case 15 and the lower case 40 each have a triangular prism shape. The upper case 15 constitutes the front and top surfaces of the housing case 101, and the lower case 40 constitutes the back and bottom surfaces of the housing case 101. The side surface of the upper case 15 is a triangle with its hypotenuse pointing downward, and the side surface of the lower case 40 is a triangle with its hypotenuse pointing upward. The rectangular housing case 101 is assembled by joining the upper case 15 and the lower case 40 at a joining surface 42 that is inclined obliquely with respect to the top surface of the upper case 15 or the bottom surface of the lower case 40 and a horizontal surface. By making each of the upper case 15 and the lower case 40 into a triangular prism shape obtained by dividing a rectangular parallelepiped case obliquely, the number of divided surfaces can be reduced, and the waterproof effect can be improved. In addition, the housing case 101 is easy to manufacture and assemble.

[0059] The upper case 15 and the lower case 40 are connected at the joint surface 42 with a sheet-like seal member 44 made of silicone rubber sandwiched therebetween to prevent dust and water droplets from entering the inside of the stereo camera device 100. In the embodiment, in order to suppress heat conduction between the upper case 15 and the lower case 40, the sheet-like seal member 44 is used to prevent the upper case 15 and the lower case 40 from coming into direct contact with each other, but this is not limiting. A general sealing method may be used, such as forming a groove in one of the upper case 15 and the lower case 40 and fitting a packing therein.

[0060] The cameras 10A and 10B and the distance measurement sensor 20 are disposed in the upper case 15. As an example, the holding member 30 to which the cameras 10A and 10B and the distance measurement sensor 20 are assembled is abutted against the front inner wall of the upper case 15 on an XY plane perpendicular to the optical axis and screwed in place. The holding member 30 can be attached to and detached from the upper case 15 while maintaining the optical positional relationship between the cameras 10A and 10B and the distance measurement sensor 20. This makes it possible to guarantee distance measurement performance without having to individually readjust the position of each optical device when the cameras 10A and 10B and the distance measurement sensor 20 are housed in the housing case 101.

[0061] Even if an external impact is applied to the housing case 101, by providing the holding member 30 separate from the upper case 15, it is possible to suppress changes in the relative positional relationship and attitude between the cameras 10A, 10B and the distance measurement sensor 20. The camera openings 16A, 16B and the distance measurement opening 17 formed in the upper case 15 may be formed in a diffusing shape (jagged) to prevent internal reflection, or may be painted matte black to avoid strong sunlight and suppress detection failures caused by disturbance light.

[0062] A cover glass 102 that covers the camera openings 16A, 16B and the distance measurement opening 17 is attached to the front of the upper case 15. The outer periphery of the cover glass 102 may be sealed with a sealing material. As described above, the cover glass 18 is made of a single sheet of glass, and even if the cameras 10A, 10B and distance measurement sensor 20 are attached and removed in an integrated state, differences in distortion and shifts in focus position that occur in each camera 10 due to variations in thickness, warping, etc. of the cover glass 18 are suppressed.

[0063] The printed circuit board 41 on which the electronic circuit 50 is attached is disposed in the lower case 40. As an example, the printed circuit board 41 on which the electronic circuit 50 is mounted is disposed on the inner bottom surface of the lower case 40. By removing the lower case 40 from the upper case 15, connection to the cable wiring 400, maintenance, and the like can be performed.

[0064] When the upper case 15 and the lower case 40 are combined, the printed circuit boards 25A, 25B and the printed circuit board 31 held in the upper case 15 and the printed circuit board 41 held in the lower case 40 are wired and connected by a flexible printed circuit (FPC) cable 48. The FPC cable 48 is folded and accommodated in the housing case 101.

[0065] Cable wiring 400 serving as an external interface includes a relay connector 45, a waterproof packing 46, and a lock nut 47. Cable wiring 400 is attached by inserting the screw portion of relay connector 45 from the outside into opening 43 formed on the back surface of lower case 40, sandwiching waterproof packing 46, and tightening lock nut 47 from the inside. This configuration of cable wiring 400 prevents water, oil, dust, and the like from entering stereo camera device 100.

[0066] In order to improve the detection resolution, it is necessary to increase the number of pixels of the image sensor. As the number of pixels of the image sensor increases, the amount of electronic information processing inevitably increases, and the heat generated by the electronic circuit 50 also increases.

[0067] In the embodiment, a heat dissipation path is provided in the lower case 40, and heat generated in the printed circuit board 41 mounting the electronic circuit 50 formed of an LSIC, FPGA, or the like is dissipated from the lower case 40 to the outside. As described above, the printed circuit board 25 mounting the image sensor 23 is joined to the base member 22 with a thermosetting or UV-curing adhesive that is difficult to transmit heat, so that heat generated in the printed circuit board 25 is mainly transferred to the printed circuit board 41 via the FPC cable 48. For example, the ground patterns of the FPC cable 48 and the printed circuit board 41 may be laminated as solid wiring, thereby efficiently transferring heat to the lower case 40.

[0068] The electronic circuit 50 mounted on the printed circuit board 41 may be adhered to the lower case 40 by heat dissipation grease. Heat dissipation grease is a paste-like resin made by mixing silicone oil with powder with good thermal conductivity, such as alumina. The electronic circuit 50 is adhered to the lower case 40 by applying heat dissipation grease to the base surface formed on the lower case 40 and assembling the printed circuit board 41 to the lower case 40.

[0069] The area of ​​the base of the lower case 40 to which the thermal grease is applied is determined based on the amount of heat (power consumption) of the heat source such as LSI, FPGA, etc., and the thermal resistance of the thermal grease. A sheet-like silicone pad or the like may be used instead of the thermal grease. In the embodiment, a paste-like heat transfer material that is in an uncured state when the printed circuit board 41 is assembled and flexibly spreads and settles according to the gap between the printed circuit board 41 and the base surface is used, so that the printed circuit board 41 is not subjected to an excessive load due to pressure.

[0070] Heat dissipation fins 401 for expanding the surface area are formed on the outer surface of the lower case 40. Heat dissipation properties may be further improved by performing a surface treatment such as black painting on the heat dissipation fins 401 and the outer surface of the lower case 40. A thermal circuit is formed so that heat transferred to the lower case 40 is efficiently radiated to the outside air and is not stored by natural convection.

[0071] As described above, the imaging function and the arithmetic processing function are shared by consolidating the optical system including the camera in the upper case 15 and disposing the electronic circuit 50 in the lower case 40. By combining the upper case 15 and the lower case 40 with the seal member 44 having a higher thermal resistance than either the upper case 15 or the lower case 40 sandwiched therebetween, heat generated in the printed circuit board 41 on which the electronic circuit 50 is mounted is dissipated from the lower case 40. The seal member 44 having a low thermal resistance acts as a buffer material to suppress heat transfer from the lower case 40 to the upper case 15. This configuration minimizes the effect of heat on the base members 22A and 22B that hold the lenses 21A and 21B, and stably maintains the positions and attitudes of the lenses 21A and 21B for a long period of time.

[0072] The stereo camera device 100 can be directly attached to a frame constituting a head guard of, for example, a forklift or a hydraulic excavator. In this embodiment, an attachment portion 49 for attaching to a vehicle is provided on the upper case 15. When the stereo camera device 100 is attached to a vehicle, the field of view can be optically adjusted to maintain the distance measurement performance of the cameras 10A and 10B.

[0073] When the stereo camera device 100 is mounted on a forklift or hydraulic excavator, it is necessary to estimate not only the contact distance between the vehicle and an object, but also the contact distance between the end of the load and the object. In a system in which the stereo camera device 100 is provided at the front and rear to enable 360-degree detection corresponding to rotational movement, it is necessary to ensure the continuity of the field of view. Therefore, when mounting the stereo camera device 100 on a vehicle, it is desirable to be able to adjust the object identification function according to the situation at the site. When it becomes necessary to update the object identification function, to malfunction the electronic circuit 50, or to replace parts due to deterioration of the seal member 44 over time, the lower case 40 can be removed while the upper case 15 holding the cameras 10A and 10B is fixed to the vehicle, and maintenance work can be performed. The stereo camera device 100 has a configuration suitable for mounting on a vehicle and can maintain distance measurement performance. The stereo camera device 100 is suitable for mounting not only on vehicles, but also on flying objects such as drones and moving objects such as ships.

[0074] The cameras 10A and 10B and the distance measuring sensor 20 are integrally held by a holding member 30 separate from the housing case 101, so that the positional relationship between the cameras 10A and 10B and the distance measuring sensor 20 is accurately maintained. If optical devices such as the cameras 10A and 10B and the distance measuring sensor 20 are directly attached to the housing case 101, the effects of vibration and heat on the optical system will be large, but the configuration of the embodiment minimizes the effects of the environment on the imaging system and maintains distance measurement accuracy. Since the holding member 30 is fixed to the upper case 15, the positional relationship between the imaging system including the cameras 10A and 10B and the distance measuring sensor 20 and the vehicle is maintained even when the lower case 40 is removed. Note that the distance measuring sensor 20 and the cameras 10A and 10B do not necessarily need to be integrally held by the holding member 30 as long as they are maintained in a predetermined positional relationship. For example, the distance measurement sensor 20 and the cameras 10A and 10B may be attached to separate holding members, and the holding members may be combined or connected together so that the positional relationship between the distance measurement sensor 20 and the cameras 10A and 10B is maintained.

[0075] The stereo camera device 100 suppresses degradation of distance measurement performance even in outdoor environments. When the stereo camera device 100 is attached to a moving object such as a vehicle or drone, it calculates the distance from the parallax regardless of the moving speed or direction of the moving object, so that it can perform object detection and distance estimation with high accuracy in close-range areas. In addition, by using a retrofocus lens, it is possible to distinguish between workers and materials in a wide-angle close-field of view with a viewing angle of 120° or more. [Explanation of symbols]

[0076] 10A, 10B Camera 13 Fitting hole (positioning means) 15 Upper case (first case member) 16A, 16B Camera opening 17 Ranging aperture 20 Distance sensor 22 Base material 25, 25A, 25B, 31, 41 Printed circuit board 30 Retaining member 30a Contact surface 40 Lower case (second case member) 42 Joint surface 43 opening (for external interface) 44 Sealing material 49 Mounting part 50 electronic circuits 50A Control Unit 51 Image processing section 52 Parallax calculation section 53 Calibration calculation section 54 Distance calculation section 55 Data Entry Section 100 Stereo camera device 101 Housing case (case) 102 Coverslip 400 Cabling (External Interface) 401 Heat dissipation fin [Prior art documents] [Patent documents]

[0077] [Patent Document 1] JP 2012-189324 A [Patent Document 2] JP 2012-167944 A [Patent Document 3] Japanese Patent Application Publication No. 11-325890

Claims

1. Multiple cameras and an electronic circuit for calculating a distance to an object based on image data captured by the plurality of cameras; a housing case that houses the cameras and the electronic circuit; having the housing case is formed of a first case member and a second case member, the cameras are disposed in the first case member, and the electronic circuit is disposed in the second case member, the first case member and the second case member are separated obliquely with respect to a bottom surface of the housing case; Stereo camera device.

2. A plurality of cameras; an electronic circuit for calculating a distance to an object based on image data captured by the plurality of cameras; a housing case that houses the cameras and the electronic circuit; having the housing case is formed of a first case member and a second case member, the cameras are disposed in the first case member, and the electronic circuit is disposed in the second case member, the first case member and the second case member are connected to each other at a joint surface that is inclined with respect to a bottom surface of the housing case, and communicate with each other internally. Stereo camera device.

3. A plurality of cameras; an electronic circuit for calculating a distance to an object based on image data captured by the plurality of cameras; a housing case that houses the cameras and the electronic circuit; having the housing case is formed of a first case member and a second case member, the cameras are disposed in the first case member, and the electronic circuit is disposed in the second case member, The first case member and the second case member are in the shape of a triangular prism. Stereo camera device.

4. The first case member constitutes a front surface and a top surface of the housing case, and the second case member constitutes a rear surface and a bottom surface of the housing case. The stereo camera device according to claim 1 .

5. the first case member has a plurality of openings exposing lens surfaces of the plurality of cameras, and the second case member has an opening receiving an external interface connected to the electronic circuit; The stereo camera device according to claim 1 .

6. The first case member and the second case member are joined with a seal member having a higher thermal resistance than either the first case member or the second case member. The stereo camera device according to claim 1 .

7. The second case member has a heat dissipation portion. The stereo camera device according to claim 1 .

8. The first case member has an attachment portion for attachment to a movable body. The stereo camera device according to claim 1 .

9. The second case member is detachable from the first case member in a state in which the first case member is attached to the movable body. The stereo camera device according to claim 8 .

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