JP2013127598A - Stereo camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stereo camera which suppresses variations in a base line length and an optical axis of two photographic optical systems due to distortion and vibration of a member caused by tightening during manufacture and adjustment, has a mounting structure with high productivity, is inexpensive, and has high reliability.SOLUTION: The stereo camera includes a stay, a first imaging section provided on one end of the stay, and a second imaging section provided on the other end of the stay. The first imaging section has a first imaging lens, a first fixing member, a first lens holder, a first camera block and a first imaging element. The second imaging section includes a second imaging lens, a second fixing member, a second lens holder, a second camera block and a second imaging element. Optical axes of the first imaging section and the second imaging section are parallel to each other, the first imaging lens is fixed to the first lens holder at three portions of the first fixing member, and the second imaging lens is fixed to the second lens holder at three portions of the second fixing member.

Description

  The present invention relates to a stereo camera that calculates parallax information from images captured from a plurality of image sensors.

  Conventionally, a stereo camera is known as a technique for measuring the three-dimensional position of a subject.

  A stereo camera device that calculates the distance to an object using a pair of images captured by two imaging means and thereby recognizes the object is an in-vehicle system or a suspicious vehicle that supports safe driving of a car. It is applied to monitoring systems that detect intruders and abnormalities.

  In particular, automobiles are equipped with cameras, radars, etc. to detect information on vehicles and obstacles ahead, and the detected information determines the risk of collision with vehicles ahead, etc. Actively develop technologies related to ASV (Advanced Safety Vehicle), such as decelerating by braking and automatically increasing or decreasing the running speed to keep the distance between the vehicle and the preceding vehicle safe. It is being advanced.

  As a vehicle collision prevention system, a system that issues an inter-vehicle distance warning, a drowsy driving warning, a pedestrian protection, and a rear obstacle warning is considered. In addition, a system for preventing lane departure, maintaining the distance between vehicles, and automatically avoiding accidents is also considered. In such a system, there is a stereo-type camera as one of distance measuring devices mounted for measuring the distance to an object.

  In this stereo camera, the distance between the two cameras (the distance between the optical axes) is set as the baseline length, and the three-dimensional position information of the subject is calculated from the parallax and the baseline length of the captured images of the two cameras. Can detect the shape of the road and multiple objects.

  This is expected to assist the driver's vision and help prevent collision accidents, and an inexpensive and highly reliable in-vehicle stereo camera is desired.

  There exists a thing like patent document 1 as such a vehicle-mounted stereo camera. The structure of this stereo camera is composed of a stay, camera block, lens holder, imaging lens, imaging device, and signal processing board, and includes two or more sets of each imaging device, and parallax (baseline length) between two or more cameras In order to perform image processing such as distance measurement to an object using the stereo, a stereo camera as an image sensor has a structure in which the optical axis accuracy is determined by a base stay.

International Publication No. 2006/052024

  In the present invention, further, the accuracy of mounting the left and right relative positions of the imaging lens including the holding structure when manufacturing the stereo camera, the processing accuracy and assembly accuracy of the mounting surface of the imaging lens holding member and the stay, It is necessary to consider.

  The object of the present invention is to suppress the base line length and optical axis fluctuation of the two photographic optical systems due to distortion and vibration of the member due to tightening during manufacture and adjustment, and a highly productive mounting structure, an inexpensive and highly reliable stereo camera Is to provide.

  In order to solve the above problems, a stereo camera of the present invention includes a stay, a first imaging unit provided at one end of the stay, and a second imaging unit provided at the other end of the stay. The first imaging unit includes a first imaging lens, a first fixing member, a first lens holder, a first camera block, and a first imaging element, and the second imaging unit includes: A second imaging lens, a second fixing member, a second lens holder, a second camera block, and a second imaging element are included, and the optical axes of the first imaging unit and the second imaging unit are parallel. In addition, the first imaging lens is fixed at three locations of the first lens holder and the first fixing member, and the second imaging lens is fixed at three locations of the second lens holder and the second fixing member. A fixed configuration is used.

  It is possible to provide a highly productive mounting structure and a low-cost and highly reliable stereo camera by suppressing the base line length and optical axis fluctuation of the two imaging optical systems due to the distortion and vibration of the members due to tightening during manufacture and adjustment.

It is a figure which shows the vehicle carrying the stereo camera which concerns on this invention. It is a perspective view which shows the whole stereo camera external appearance which concerns on this invention. It is a figure which shows the cross section of the lens holder of the stereo camera which concerns on this invention. It is a figure explaining the inscribed circle of a triangle concerning the present invention. It is a figure explaining the inscribed circle of the polygon concerning the present invention. It is a figure explaining the inscribed circle size difference in the triangle concerning the present invention. It is a perspective view which shows the whole external stereo camera external appearance of the stay and imaging part of this invention. It is a perspective view which shows the other shape of the lens holder of the stereo camera which concerns on this invention. It is a perspective view which shows the other shape of the lens holder of the stereo camera which concerns on this invention, and the other shape of an imaging lens. It is a figure explaining the relative positional relationship of the lens contact surface arrange | positioned at two of the stereo cameras concerning this invention.

  Hereinafter, the stereo camera according to the present invention will be described in detail with reference to the illustrated embodiments.

  First, an in-vehicle stereo camera, which is an application example of the stereo camera of the present invention, will be described with reference to FIG.

  For example, as shown in FIG. 1, a stereo camera 2 is attached to a vehicle 1 such as an automobile, an object within a predetermined range in front of the vehicle 1 is imaged, and an object outside the vehicle is recognized and monitored from the captured image.

  The stereo camera 2 is arranged at a position that does not block the driver's field of view, such as near the rear mirror of the vehicle 1. The image captured by the stereo camera 2 is processed to calculate three-dimensional distance distribution information, road shapes and three-dimensional positions of a plurality of three-dimensional objects are detected at high speed from the calculated distance distribution information, and based on the detection results. When the preceding vehicle or obstacle is identified and collision warning judgment processing is performed, and the recognized object is an obstacle of the vehicle 1, it is displayed on the display device 3 installed in front of the driver and displayed to the driver. In addition to warning, automatic collision avoidance control of the vehicle body can be performed by connecting an external device that controls actuators (not shown).

  The stereo image processing used in these systems is to obtain a distance by applying a triangulation technique to a pair of captured images that are imaged at a positional interval. In general, a pair of imaging units and a stereo image processing LSI that performs triangulation processing on a pair of captured images output by these imaging units are provided.

  At this time, the stereo image processing LSI obtains the pixel position of the feature point common to each other image from the pixel information included in the pair of images and the number of pixels in which the feature point is shifted in the pair of images. Triangulation processing is realized by performing processing.

  Therefore, it is ideal that there is no deviation other than parallax between the pair of images, and it is necessary to adjust each imaging unit so that there is no deviation in optical characteristics and signal characteristics. Especially in the in-vehicle environment, for example, there is an application request to detect a vehicle ahead, a person, an obstacle, etc., and deal with it safely in advance, so it is necessary to reliably measure and recognize a distance object. .

  The importance of the relative positional relationship between the left and right imaging optical systems in a stereo camera generally requires that there is no deviation other than the above-described parallax as the object becomes farther.

Next, an example of an application form in the stereo camera of the present invention will be described with reference to FIG.
FIG. 2 shows an overall appearance of the stereo camera 2 of FIG. 1, and each function will be described later.

  The configuration of the stereo camera 2 according to the present embodiment includes two image pickup devices 9a and 9b (first image pickup device and second image pickup device) and two image pickup lenses 5a and 5b (first image pickup lens and second image pickup device). Lens), lens holders 6a and 6b (first lens holder and second lens holder) for holding the imaging lenses 5a and 5b, the imaging elements 9a and 9b, and the lens holders 6a and 6b. Camera blocks 8a, 8b for holding and holding plates 7a, 7b (first fixing member, second fixing member) of fixing members that are positioned opposite to the lens holders 6a, 6b and fix the imaging lenses 5a, 5b An image processing device 10a, 10b that performs processing for capturing image information imaged on the image sensors 9a, 9b into the image processing LSI and an image processing LSI that performs stereo processing using the captured image information are mounted. Composed of the stay 4 to implement them as image processing board (not shown).

  That is, the stay 4 has a first image pickup unit provided at one end of the stay 4 and a second image pickup unit provided at the other end of the stay. An imaging lens 5a that is an imaging lens, a pressing plate 7a that is a first fixing member, a lens holder 6a that is a first lens holder, a camera block 8a that is a first camera block, and an imaging that is a first imaging element. The second imaging unit includes an imaging lens 5b as a second imaging lens, a holding plate 7b as a second fixing member, a lens holder 6b as a second lens holder, and a second imaging unit. The camera block 8b, which is a camera block, and an image sensor 9b, which is a second image sensor, are provided.

At this time, the optical axes of the image sensor 9a and the image sensor 9b need to be parallel.
The imaging lenses 5a and 5b form visual information of the outside world on the imaging elements 9a and 9b.

  The stay 4 includes camera blocks 8a and 8b of a camera unit including imaging element substrates 10a and 10b on which imaging elements 9a and 9b are mounted, imaging lenses 5a and 5b, and lens holders 6a and 6b on which pressing plates 7a and 7b are mounted. It is a member to hold.

  The imaging device substrates 10a and 10b are substrates on which the imaging devices 9a and 9b are mounted, and an electronic circuit for transmitting image information captured by the imaging devices 9a and 9b to an image processing substrate (not shown) is configured. It is a substrate, and performs processing for capturing image information formed on the image sensors 9a and 9b into an image processing LSI mounted on an image processing substrate (not shown).

  The image processing board (not shown) extracts the processing object by the image processing LSI based on the image information sent from the imaging element boards 10a and 10b, and calculates the distance and size to the processing object. It is the board | substrate with which the electronic circuit for doing is comprised.

  Next, an imaging lens holding structure having three or more support points used in the stereo camera of the present invention will be described later with reference to FIGS. 3, 4, 5, and 6.

  FIG. 3 is a cross-sectional view in a state in which the imaging lens 5 is mounted on the lens holder 6 and the imaging lens 5 is fixed with a fastening member such as a screw from above the imaging lens 5 using a pressing plate 7.

  The imaging lens holding structure having three or more supporting points used for the stereo camera 2 has one contact point between the upper part of the imaging lens 5 and the lower part of the pressing plate 7 when the pressing plate 7 is in the upward direction and the lens holder 6 is in the downward direction. There are a total of three points, two contact points between the lower left and right of the imaging lens 5 and the lower left and right inside the lens holder 6.

  In examining the optimum shape of the imaging lens holding structure used in the stereo camera of the present invention, the virtual lens holder 6 and the virtual pressing plate 7 are polygons, and the virtual imaging lens 5 is an inscribed circle.

  4 shows an inscribed circle (imaging lens 5) in a triangle (lens holder 6), an isosceles triangle 11a, an equilateral triangle 11c, and a triangle 11b having three different lengths. FIG. It becomes a trapezoid 12b, a pentagon 13a, and a hexagon 13b.

  In the shape of the prior art, it is joined by a combination of a cylindrical imaging lens and a cylindrical lens holder of the same size, but in reality there is a tolerance between the imaging lens barrel and the lens holder. The diameter of the lens holder that supports the lens barrel is larger than the diameter of the lens barrel.

  In this case, since the number of support points is two when the imaging lens is fixed, the position of the imaging lens is not uniquely determined, and the position before and after fixing is easily changed.

  From this, if the shape is a polygon rather than a triangle, the number of fixed points of the imaging lens will be 3 or more, and even if the length of each side is different, an inscribed circle is possible. Is a preferred shape as a structure in which is uniquely determined.

  Further, as a merit of the lens holder having a polygonal shape, it will be described with reference to FIG. 6 that even when the diameter of the imaging lens is changed, it is not necessary to change the shape of the lens holder each time.

  When the virtual imaging lens small 14 and the virtual imaging lens large 15 having different diameter sizes are mounted on the virtual lens holder 16, the virtual pressing plate small 17 can be changed to the virtual pressing plate large 18.

  In the conventional circular lens holder, it is necessary to change the shape of the lens holder in accordance with the diameter of the imaging lens.

  As described above, the optical axes of the imaging element as the first imaging unit and the imaging element as the second imaging unit are parallel, and the two imaging lenses have three or more locations on the lens holder and the pressing plate that is a fixing member. With the configuration fixed at the same time, the base line length due to vibration and the imaging lens are maintained while maintaining sufficient mechanical strength even when mounted in harsh environments such as automobiles, etc. It is possible to provide a highly productive mounting structure and an inexpensive and highly reliable stereo camera capable of minimizing optical axis fluctuations, eliminating errors, and maintaining an allowable range of accuracy.

  Next, a stereo camera characterized in that the stay 4, the camera blocks 8a and 8b, and the lens holders 6a and 6b according to the first embodiment are integrated with each other will be described with reference to FIG.

  In the first embodiment, as a connection portion including a tolerance, a machined surface is formed at both ends of the stay 4 at positions where the camera blocks 8a and 8b are mounted, and a lower surface is machined on the same surface. The machined surfaces of the camera blocks 8a and 8b are connected to each other.

  Further, the machined surfaces including tolerances are similarly connected to the connecting surfaces of the camera blocks 8a and 8b mounted on both ends of the stay 4 and the lens holders 6a and 6b having an imaging lens holding function. .

  The configuration of FIG. 7 according to the second embodiment is an integrated configuration in which the lens holder integrated stay 19 includes the camera blocks 8a and 8b and the lens holders 6a and 6b of FIG. Other configurations are the same as those of the first embodiment shown in FIG.

  In the above configuration, after assembling the two camera units separately, the number of joints including a tolerance is reduced by four compared to the first embodiment attached to the stay, thereby improving the relative position accuracy of the two imaging units. The measurement accuracy of the stereo camera can be improved with a simple structural component configuration.

  Furthermore, by adopting a structure that reduces the number of fastening members, it is possible to reduce mass production variation and secular change of the stereo camera casing structure.

  As a result, it is possible to provide a stereo camera with improved reliability in a stereo camera to be mounted on an automobile that is subjected to particularly severe stress both in terms of temperature and mechanical properties.

  Surfaces obtained by machining only the contact surface of the imaging lens 5 with high accuracy, with the contact portions (contact surfaces in this embodiment) of the lens holders 6a and 6b of the first embodiment as the second shape. A stereo camera featuring the above will be described with reference to FIG.

  2 and 3, the preferred shape of the imaging lens holding structure has been described using an inscribed circle in which the cross section is triangular and the imaging lens is supported at three points.

  In this case, the surface to be machined that requires flatness is the entire inner lower portion of the lens holder 6, and parts other than the contact surface with the imaging lens are machined with high accuracy.

  With the structure in which the imaging lens barrel is in contact with two convex portions on the inner lower side of the lens holder second shape 20 in FIG. 8 and in one location on the pressing plate 7, only the area of the convex portion is accurately machined. When processing the entire inner surface of the lens holder, which is the contact surface of the imaging lens, by supporting the imaging lens holding 3-point support that reduces the processing cost by reducing the processing area, and maintaining the support cross-sectional shape as a triangle. It is possible to obtain equivalent performance.

  The lens holder 6a and the imaging lens 5 according to the first embodiment are provided with convex portions on the lens holder 6 and the imaging lens 5 with a third shape as a contact portion (contact surface in this embodiment) with the imaging lenses 5a and 5b. A stereo camera characterized in that the convex portion and the concave portion are aligned will be described with reference to FIG.

  The lens holder third shape 21 has a convex portion and a concave portion on the contact surface with the imaging lens, and the imaging lens second shape 22 has a convex portion that fits in the concave portion of the lens holder third shape 21. Thus, the convex / concave portion of the imaging lens is settled, and the pressing plate 7 for fixing the imaging lens has a structure for pressing the imaging lens from the facing direction of the lens holder.

  Also in the imaging lens holding structure of the fourth embodiment, the shape inside the lens holder forms a triangle, and the imaging lens is configured to be accommodated therein, and the imaging lens is always supported at three or more points.

  As a merit of the convex and concave portions, when moving the imaging lens in the front-rear direction in the focus adjustment of the stereo camera, by having the convex and concave portions on the lens holder side, the initial mounting position of the imaging lens can be mounted closer to the optimum focus position. Therefore, it is possible to reduce the time for focus adjustment, and the adjustment cost can be reduced.

  Furthermore, when compared with an imaging lens holding structure having no convex and concave portions, there is also an advantage that the imaging lens does not fall out of the lens holder even in a manufacturing process such as focus adjustment and a vibration environment such as in-vehicle, and the reliability is improved. .

  As described above, the embodiment of the present invention has been described. According to the present invention, a high function is achieved by reviewing the structure shape for holding the imaging lens and reducing the number of fastening members used for connecting the members of the imaging unit. This makes it possible to realize the multi-function stereo camera at a low cost without deteriorating the overall characteristics.

  Contact surfaces 23a (first contact locations), 23b (third contact locations) and 23c (second contact locations), which are contact locations of the lens holders 6a and 6b of the first embodiment with the imaging lenses 5a and 5b. A stereo camera characterized by a highly accurate machined surface in which 23d (fourth contact location) is parallel and has a high degree of parallelism will be described with reference to FIG.

  In the second embodiment, as shown in FIG. 7, the lens holder integrated stay 19 includes the camera blocks 8a and 8b and the lens holders 6a and 6b in FIG. The accuracy is improved and the measurement accuracy of the stereo camera can be improved.

  When machining the contact surfaces 23a, 23b, 23c, and 23d of the present embodiment, the processing variation is suppressed by making the processing directions the same, and the relative positional accuracy of the four contact surfaces is improved.

  As a result, the imaging lenses 5a and 5b located at two locations separated from the base line length of the lens holder integrated stay 19 are mounted on the contact surfaces 23a and 23c and 23b and 23d with high relative positional accuracy, thereby providing 2 The accuracy of the optical axis parallelism of each of the imaging lenses 5a and 5b located at the locations is improved.

  In this case, the parallelism of the machined surfaces of the contact surfaces 23a, 23b, 23c, and 23d of the imaging lens 5 located at two locations can be measured by a three-dimensional coordinate position.

  The three-dimensional measuring method is expressed in three dimensions of length, width, and height, and each is usually referred to as X, Y, and Z, and is a machining reference point of the lens holder integrated stay 19 that is an object to be measured. A surface having a reference position is used as a reference surface for parallelism measurement, and the surfaces calculated from the three-dimensional coordinates of the contact surfaces 23a, 23b, 23c, and 23d on the surface, 23a and 23b, and 23c and 23d. Measure parallelism.

  Other configurations are the same as those of the second embodiment shown in FIG.

  A stereo camera characterized in that the contact surface of the lens holder 6 of the first to fifth embodiments with the imaging lens 5 has a high surface roughness will be described. (Not shown)

  The unevenness of the contact surface of the lens holder 6 with the imaging lens 5 is measured in units of micrometers, and the numerical value thereof is referred to as “surface roughness”.

  As an example in which the imaging lens 5 is mounted on the lens holder 6, the unevenness of the contact surface of the lens holder 6 of the imaging lens 5 is engaged with the unevenness of the contact surface of the imaging lens 5 of the lens holder 6.

  In this case, it is necessary to move the imaging lens 5 in the longitudinal direction of the optical axis when performing focus adjustment at the time of manufacture. In this case, depending on the relationship between the surface roughness of the lens holder 6 and the surface roughness of the imaging lens 5, the longitudinal direction of the optical axis. There is a possibility that the movement of

  For example, if there is an optimum focus adjustment position of the imaging lens 5 at a location where the irregularity spacing of the contact surface of the imaging lens 6 of the lens holder 6 is larger than the focus adjustment accuracy of the imaging lens 5, it is moved for focus adjustment. Even if the lens is desired to be placed at the optimum focus position, the imaging lens 5 moves to the next unevenness, and the adjustment is made at a position where the lens performance is deteriorated by deviating from the optimum focus position.

  Thus, at the time of focus adjustment in which the components slide, it is necessary to smoothly finish the contact surface of the imaging lens 5 of the lens holder 6 and the surface of the contact surface of the lens holder 6 of the imaging lens 5. It is required as the dimensional tolerance of the surface roughness on the lens holder side that the unevenness of the contact surface of the imaging lens 5 of the lens holder 6 is sufficiently smaller than the adjustment accuracy.

  As another form, by forming a stitch line in a direction perpendicular to the machining line of the lens holder 6 when machining the contact machining surface with the imaging lens 5 and the stitch line formed when machining the lens barrel of the imaging lens 5, the focus adjustment is performed. When the image pickup lens 5 is moved, the streak and the streak are not engaged with each other. Therefore, the minimum operating distance of the image pickup lens 5 does not depend on the streak interval.

  In addition to making the machining lines of the lens holder 6 and the machining lines of the imaging lens 5 perpendicular to each other, the same effect can be obtained by applying paint to the ground of the machined surface and filling the unevenness of the machined lines to be fitted. Can be obtained.

  Further, the contact surface second shape 24 (see FIG. 9) with the imaging lens 5 that reduces the area of the contact processing surface between the lens holder 6 and the imaging lens 5 reduces the machining surface with high accuracy. Processing costs can also be reduced. Advantages include not only machining cost but also improvement of machining accuracy and surface roughness accuracy by shortening the machining time on the same surface, leading to suppression of thermal deformation of the machine due to heat generated during machining.

  Furthermore, the second contact surface shape 24 with the imaging lens 5 reduces the sliding resistance between the imaging lens 5 and the lens holder 6 during focus adjustment.

  In particular, by reducing the sliding resistance, the force for moving the imaging lens 5 at the time of focus adjustment can be reduced, so that the minimum operating distance of the imaging lens 5 can be finely operated.

As another method of reducing the sliding resistance with the imaging lens 5 by reducing the friction coefficient, the volatile lubricant is used to move the imaging lens 5 while reducing the sliding resistance only during focus adjustment. After the focus adjustment, the imaging lens 5 can be fixed by increasing the sliding resistance by volatilizing the lubricant.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Stereo camera 3 Display apparatus 4 Stay 5 Imaging lens 6 Lens holder 7 Holding plate 8 Camera block 9 Image sensor 10 Image sensor board 11 Triangular inscribed circle 12 Square inscribed circle
13 Hexagonal inscribed circle 14 Virtual imaging lens small 15 Virtual imaging lens large 16 Virtual lens holder 17 Virtual pressing plate small 18 Virtual pressing plate large 19 Lens holder integrated stay 20 Lens holder second shape 21 Lens holder third shape 22 Imaging Lens second shape 23 Contact surface 24 Contact surface second shape

Claims (5)

Stay and
A first imaging unit provided at one end of the stay;
A second imaging unit provided at the other end of the stay,
The first imaging unit includes a first imaging lens, a first fixing member, a first lens holder, a first camera block, and a first imaging element,
The second imaging unit includes a second imaging lens, a second fixing member, a second lens holder, a second camera block, and a second imaging element,
The optical axes of the first imaging unit and the second imaging unit are parallel, and
The first imaging lens is fixed at three locations of the first lens holder and the first fixing member,
The second imaging lens is a stereo camera that is fixed at three locations of the second lens holder and the second fixing member. The stereo camera according to claim 1,
A stereo camera in which the stay, the first camera block, the second camera block, the first lens holder, and the second lens holder are integrated. The stereo camera according to claim 1,
A stereo camera in which the first lens holder and the second lens holder have a convex structure at a contact point with the first imaging lens and the second imaging lens. The stereo camera according to claim 1,
The first lens holder and the second lens holder have convex and concave portions at contact points with the first imaging lens and the second imaging lens,
A stereo camera in which a convex portion of the first imaging lens, the second imaging lens, a concave portion of the first lens holder, and a concave portion of the second lens holder are fitted. The stereo camera according to claim 1,
The first lens holder has a first contact location and a second contact location that contact the first imaging lens;
The second lens holder has a third contact location and a fourth contact location that contact the second imaging lens,
The first contact point and the third contact point are parallel,
A stereo camera in which the second contact location and the fourth contact location are parallel.