Patent Publication Number: US-2018054552-A1

Title: Imaging Device

Description:
TECHNICAL FIELD 
     The present invention relates to an imaging device. 
     BACKGROUND ART 
     Conventionally, there has been proposed an imaging device having a structure in which an imaging substrate and another substrate are connected by a cable (For example, PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2014-157309 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, in a structure in which an imaging substrate and another substrate are connected by a cable, the cable is usually made as short as possible in consideration of noise resistance. In particular, in a case where an imaging substrate is secured to another substrate as in PTL 1, since the relative positional relationship between the imaging substrate and the other substrate is determined beforehand, the necessity of the cable having an excess length is low. In addition, in a structure in which an imaging substrate and another substrate are connected linearly, it is a great advantage that the substrates can be connected to each other by a cable at the shortest distance. Therefore, the cable is made as short as possible. 
     However, even though a cable connecting an imaging substrate and another substrate is preferably short from the viewpoint of noise resistance, there is a drawback that manufacturing workability is inferior. 
     Therefore, an object of the present invention to provide an imaging device in which an imaging substrate and another substrate are connected by a cable and which can satisfactorily suppress the influence of noise caused by the cable while achieving improved manufacturing workability. 
     Solution to Problem 
     The present invention includes: an imaging substrate which is provided with an imaging element; a signal processing substrate which processes a signal from the imaging element; and a belt-shaped cable which connects the imaging substrate and the signal processing substrate. Securing parts to which both ends of the belt-shaped cable are secured are provided on the imaging substrate and the signal processing substrate, respectively. The imaging substrate and the signal processing substrate are disposed so as to have a positional relationship in which regions in a longitudinal direction of the respective securing parts overlap each other in a crossing direction crossing the longitudinal direction. The belt-shaped cable has a bent part to which a bending tendency is given and which is provided in at least a portion between the both ends. 
     Alternatively, the present invention includes: an imaging substrate which is provided with an imaging element; a signal processing substrate which processes a signal from the imaging element; and a belt-shaped cable which connects the imaging substrate and the signal processing substrate. Relative positions of the imaging substrate and the signal processing substrate can be adjusted. A securing part to which an end of the belt-shaped cable is secured is provided on at least one of the imaging substrate and the signal processing substrate. The belt-shaped cable has a bent part to which a bending tendency given and which is provided at least in a portion between the both ends. 
     Advantageous Effects of Invention 
     According to the present invention, in an imaging device in which an imaging substrate and another substrate are connected by a cable, it is possible to satisfactorily suppress the influence of noise caused by the cable while achieving improved manufacturing workability. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a positional relationship between an imaging substrate and a signal processing substrate in a state where an imaging device according to Embodiment 1 of the present invention is mounted on a vehicle. 
         FIG. 2  is a view illustrating an outer appearance of the imaging device according to Embodiment 1. 
         FIG. 3  is a developed view of a state where a cover of the imaging device according to Embodiment 1 is removed, ( a ) is a view seen from the vertical direction, and ( b ) is a perspective view. 
         FIG. 4  is a view of a signal processing substrate of the imaging device according to Embodiment 1 as seen from the vertical direction. 
         FIG. 5  is a cross-sectional view taken along line B-B in  FIG. 3( a ) , in which ( a ) is a cross-sectional view in the case of using a cable to which a bending tendency is not given as a cable connecting the imaging substrate and the signal processing substrate, and ( b ) is a cross-sectional view in the case of using a cable having bent parts to which a bending tendency is given as a cable connecting the imaging substrate and the signal processing substrate. 
         FIG. 6  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 2, in which an insulator is disposed between a cable and an electronic component and between the cable and a cover, as compared with the structure illustrated in  FIG. 5( b ) . 
         FIG. 7  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 3. 
         FIG. 8  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 4. 
         FIG. 9  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 5, and is a view in which a connector on the imaging substrate and a connector disposed on a surface of the signal processing substrate, the surface closer to the imaging substrate, are connected. 
         FIG. 10  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 6, and is a view illustrating a state where a connector on the imaging substrate and a connector disposed on a surface of the signal processing substrate, the surface closer to the imaging substrate, are disposed at locations overlapping each other in the vertical direction, and a cable is housed between the imaging substrate and a cover. 
         FIG. 11  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 7, which illustrates a connecting structure in which a cable is housed in a space formed by the imaging substrate and the signal processing substrate. 
         FIG. 12  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 8, which illustrates a connecting structure in which the cable insertion direction into a connector on the signal processing substrate is opposite to that in  FIG. 9 . 
         FIG. 13  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 9, which illustrates a structure in which a cable extends from a connector on the signal processing substrate, passes through an insertion hole provided in the signal processing substrate, and is connected to a connector on the imaging substrate. 
         FIG. 14  is a cross-sectional view illustrating a cable connecting structure between an imaging substrate and a signal processing substrate of an imaging device according to Embodiment 10, which illustrates a structure in which a cable extends from a connector disposed on a surface of the signal processing substrate, the surface opposite to a surface of the signal processing substrate closer to the imaging substrate, passes through an insertion hole, and is connected to a connector on the imaging substrate. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Prior to a description of embodiments, a stereo camera as an imaging device will be described. Note that in the following description, since the stereo camera is described as an example of the imaging device, the imaging device may be appropriately referred to as the “stereo camera”. 
     In recent years, due to growing awareness of preventive safety, a stereo camera which enables accurate distance measurement has attracted attention with a view to avoiding collision against a target such as a preceding vehicle or a pedestrian by mounting the stereo camera on a vehicle and obtaining the distance to the target. In a stereo camera, a plurality of imaging elements is mounted. Furthermore, there is a growing need to mount a stereo camera not only on large and medium vehicles but also on small vehicles such as a mini vehicle. However, since a stereo camera includes two cameras and obtains the distance to a target by applying a triangulation technique on images captured by the two cameras, the stereo camera tends to become large in size. In addition, a stereo camera obtains the distance based on a displacement (parallax) of each pixel of images captured by the two cameras. Depending on optical axis deviation due to a design or manufacturing error, characteristic variation of the imaging element due to heat, noise or the like, accuracy of the obtained distance may be lowered. 
     Hereinafter, embodiments of a compact stereo camera according to the present embodiment will be described in detail below with reference to the drawings.  FIG. 1  is a view illustrating a positional relationship between an imaging substrate  20  including an imaging element  10  and a signal processing substrate  21  on which a processing circuit which processes a signal from the imaging element  20  is mounted, in a stereo camera mounted in a vehicle.  FIG. 1( a )  is a cross-sectional view of the stereo camera in a case where the imaging substrate  20  is located behind the signal processing substrate  21 .  FIG. 1( b )  is a cross-sectional view in a case where the imaging substrate  20  is located in front of the signal processing substrate  21 . Note that the signal processing substrate may also be referred to as a main substrate. Note that downsizing of the stereo camera can be realized by disposing a plurality of imaging substrates  20  at locations overlapping the signal processing substrate  21  and shortening the base line length. 
       FIG. 2  is a view illustrating the outer appearance of the stereo camera according to the present embodiment. This stereo camera is configured of a first imaging unit  30  (left imaging unit), a second imaging unit  31  (right imaging unit), and a housing (a holding member  2  and a cover  3 ) in which the first imaging unit  30  is disposed on one side and the second imaging unit  31  is disposed on the other side. The stereo camera generates a distance image by calculating parallax from images captured by the first imaging unit  30  and the second imaging unit  31 , and recognizes a target in front of the vehicle based on the distance image. At that time, recognition accuracy can be improved by disposing the first imaging unit  30  and the second imaging unit  31  such that the optical axes of the first imaging unit  30  and the second imaging unit  31  are parallel to each other. Therefore, it is preferable that the optical axis can be adjusted for each imaging substrate. 
       FIG. 3  is a developed view of a state where the cover  3 , which is part of the housing of the stereo camera, is removed.  FIG. 3( a )  is a developed view seen from A in  FIG. 2 , and ( b ) is a perspective view. Here, the holding member  2  and the cover  3  constituting the housing are so-called metal members. 
     In the holding member  2 , the two imaging substrates  20  (a first imaging substrate (left imaging substrate) and a second imaging substrate (right imaging substrate)) are provided. The two imaging substrates  20  include the two imaging elements  10  (a first imaging element (a left imaging element) and a second imaging element (a right imaging element)), and the connectors  4  (a first communication connecting unit and a second communication connecting unit) that are communication connecting units which each output a captured image captured by the imaging element  10  to the signal processing substrate  21  on which the processing circuit is mounted. 
     The two imaging substrates  20  are disposed to be bilaterally symmetric with respect to the longitudinal center of the holding member  2  and are disposed side by side along an identical plane. In addition, the two imaging substrates  20  are disposed such that the two imaging substrates  20  overlap the signal processing substrates  21  in the direction extending between the two imaging substrates. In addition, the imaging substrate  20  and the signal processing substrate  21  are disposed such that the planes along the respective substrates cross each other. 
       FIG. 4  is a view of the signal processing substrate  21  as seen from the vertical direction. A power supply unit  32 , a video processing unit  33 , and a recognition processing unit  34  are disposed on the signal processing substrate  21 . Two connectors  5 , which are communication connecting units with the imaging substrate  20 , are provided on an opposite mounting surface (rear surface) of the signal processing substrate  21 . At that time, the connector  4  provided on the imaging substrate  20  and the connector  5  provided on the signal processing substrate  21  are disposed such that the positions of the connectors in the longitudinal direction overlap each other. Specifically, the connector  4  of the imaging substrate  20  and the connector  5  of the signal processing substrate  21  are disposed so as to have a positional relationship in which regions in the longitudinal direction of the connector  4  and the connector  5  overlap each other in a crossing direction crossing the longitudinal direction. 
     In a case where the connector  4  of the imaging substrate  20  and the connector  5  of the signal processing substrate  21  are disposed so as to overlap each other in the longitudinal direction of the connectors, since the connector  4  and the connector  5  are in a so-called linear arrangement, it is conceivable to take advantage of proximity of the connectors to make the cable  40  as short as possible. In contrast, considering connection workability between the connectors, a longer cable  40  is easier to handle. 
       FIG. 5  is a cross-sectional view taken along line B-B of  FIG. 3( a ) , and the cover  3  is also illustrated here. In this example, a relatively long cable  40  is used in consideration of connection workability.  FIG. 5( a )  is a cross-sectional view in a case where the connector  4  of the imaging substrate  20  and the connector  5  of the signal processing substrate  21  are connected and assembled without particularly improving a cable  40 .  FIG. 5( b )  is a cross-sectional view in a case where a cable  40  connecting the connector  4  and the connector  5  has bent parts  40   a,    40   b  to which a bending tendency is given (which are bent). 
     In the example of  FIG. 5( b ) , the two bent parts  40   a,    40   b  are formed on the cable  40 . 
     The bent part  40   a  is disposed in a space S 1  surrounded by the imaging substrate  20  and the signal processing substrate  21 . In a case where the cover  3  is attached, the space S 1  is a space surrounded by the imaging substrate  20 , the signal processing substrate  21 , and the cover  3 . 
     In addition, the bent part  40   b  is disposed in a space S 2  surrounded by the imaging substrate  20 , the signal processing substrate  21 , and the holding member  2 . Note that in a case where it is assumed that surfaces of the imaging substrate  20  and the signal processing substrate  21 , the surfaces facing the space S 1 , are front surfaces, the space S 2  is a space surrounded by rear surfaces opposite to the front surfaces of the imaging substrate  20  and the signal processing substrate  21  and the holding member  2 . 
     In addition, the cable  40  has a so-called S shape where the cable  40  is secured to the signal processing substrate  21  at one end, is directed toward the imaging substrate  20 , is folded back in front of the imaging substrate  20 , is directed away from the imaging substrate  20 , is folded back again, and is secured to the imaging substrate  20  at the other end. 
     In the case of  FIG. 5( a ) , since the cable  40  does not have a bent part to which a bending tendency is given, the cable  40  is naturally curved due to a force of returning to a flat shape. At that time, the storage form of the cable  40  may change for each product. Furthermore, since the cable  40  comes into contact with an electronic component  35  on the signal processing substrate  21 , noise and heat from the electronic component  35  are transmitted to the imaging substrate  20 , and thus characteristic variation of the imaging element  10  occurs and parallax accuracy deteriorates. Similarly, the cable  40  also comes into contact with the conductive cover  3 , which lowers parallax accuracy for the same reason. 
     In contrast, in  FIG. 5( b ) , since the connector  4  and the connector  5  are connected to each other by the cable  40  having the bent parts to which a bending tendency is given, the cable  40  and the electronic component  35  are separated from each other and the cable  40  and the cover  3  are separated from each other. Therefore, the influence of noise and heat can be eliminated. Note that as the cable  40 , a cable which is bent and to which a bending tendency is given before connecting the connector  4  and the connector  5 , or a cable which is bent and to which a bending tendency is given after connecting the connector  4  and the connector  5  may be used. Whether or not a bending tendency is given to the cable  40  is judged based on the shape of the cable  40  in a natural state where an external force is not applied to the cable  40 , the natural state being brought about, for example, by removing the cable  40  from the connectors  4  and  5 . In a case where the shape does not become flat even in the natural state, it can be judged that a bending tendency is given. 
     In addition, in the imaging device according to the present embodiment, the imaging substrate  20 , the signal processing substrate  21 , and the cable  40  are separately formed, and various assembling methods are conceivable. One of the conceivable methods is as follows. One end of the cable  40  is connected to the signal processing substrate  21 . Then, the signal processing substrate  21  is secured to the holding member  2 , and the imaging substrate  20  is separately secured to the holding member  2 . Finally, the other end of the cable  40  is connected to the imaging substrate  20 . In addition to this, the following method is also conceivable. First, the cable  40  is connected to the imaging substrate  20  and the signal processing substrate  21  so as to integrate the three members. Then, the imaging substrate  20  and the signal processing substrate  21  are secured to the holding member  2 . Whatever assembly method is adopted, upon assembly, the distance between the imaging substrate  20  and the signal processing substrate  21  changes since the relative positional relationship between the imaging substrate  20  and the signal processing substrate  21  changes. Therefore, the cable  40  preferably has an excess length. In contrast, since shape retainability is exhibited due to existence of the bent parts  40   a ,  40   b  after assembly, the cable  40  is well fitted and excellent in noise resistance as described above. 
     Normally, in a case where the imaging substrate  20  and the signal processing substrate  21  are disposed such that regions in the longitudinal direction of the connectors  4 ,  5  overlap each other in the crossing direction crossing the longitudinal direction as in this imaging device, the connector  4 ,  5  have a linear positional relationship. Therefore, the connectors  4 ,  5  can be connected to each other at the shortest distance. In the structure of the present embodiment, in order to improve connection workability by intentionally suppressing the above-described advantage, the cable  40  is made relatively long, and the bent parts are formed in consideration of fitting of the cable  40  after completion. 
     In addition, the imaging substrate  20  is configured such that the relative position with respect to an optical system  7  can be adjusted in order to adjust the positional relationship between the imaging element  10  on the imaging substrate  20  and the optical system  7  (so-called optical axis adjustment). Since the cable  40  has an excess length, workability of adjustment of the relative position and the degree of freedom of an adjustment range can be enhanced. In addition, in a case where a plurality of imaging substrates is provided as in a stereo camera, the position of each of the imaging substrates  20  is adjusted with respect to the signal processing substrate  21 . Therefore, the structure of the cable considering both workability and shape retainability is particularly useful for a stereo camera. 
     As described, in the imaging device according to the present embodiment in which the imaging substrate and the other substrate are connected by the cable, it is possible to satisfactorily suppress the influence of noise caused by the cable while achieving improved manufacturing workability. Furthermore, it is possible to suppress deterioration in parallax accuracy caused by the influence of noise and heat while securing workability of optical axis adjustment and to shorten the base line length so as to enable downsizing of the imaging device. 
       FIG. 6  is a cross-sectional view in which an insulator  50  is further disposed between the cable  40  and the electronic component  35  and between the cable  40  and the cover  3  in  FIG. 5( b ) . Even in a structure in which the cable  40  has a folded part formed in advance, there is a possibility that the cable  40  will come in contact with the electronic component  35  or the cover  3  due to vibration of the vehicle. Therefore, it is possible to avoid the influence of noise and heat by disposing the insulator  50  in each of the space between the cable  40  and the electronic component  35  and the space between the cable  40  and the cover  3 . 
       FIG. 7  illustrates an example in which a connector  5  is arranged on a front surface of a signal processing substrate  21 . In this case, in addition to the above-described assembly methods, the following method is also conceivable. First, an imaging substrate  20  and the signal processing substrate  21  are secured to a holding member  2 . Then, a cable  40  is connected to the imaging substrate  20  and the signal processing substrate  21 . Even in such a structure, bent parts  40   a,    40   b  of the cable  40  exhibit the effect of improving workability and noise resistance. 
     The above embodiment illustrates a case where the imaging substrate  20  is located in front of the signal processing substrate  21 . However, a similar effect can be obtained even in a case where an imaging substrate  20  is located behind a signal processing substrate  21 . 
       FIG. 8  illustrates a structure for connecting a connector  4  of an imaging substrate  20  and a connector  5  disposed on a rear surface of a signal processing substrate  21 . In this structure, a bent part  40   b  disposed in a space S 2  surrounded by the imaging substrate  20 , the signal processing substrate  21 , and a holding member  2  is provided on a cable  40 . Therefore, the cable  40  is separated at a distance from the holding member  2  so as not to come into contact with the holding member  2 . 
       FIG. 9  illustrates a structure for connecting a connector  4  of an imaging substrate  20  and a connector  5  arranged on a surface of the signal processing substrate  21 , the surface closer to the imaging substrate. Bent parts  40   a  are provided at a plurality of locations. In addition, in the example of  FIG. 9 , the three bent parts  40   a  are disposed in a space S 1  surrounded by the imaging substrate  20  and the signal processing substrate  21 , and one bent part  40   b  is disposed in a space S 2  surrounded by the imaging substrate  20 , the signal processing substrate  21 , and a holding member  2 . 
       FIG. 10  is a connection diagram illustrating a case where a connector  4  of an imaging substrate  20  and a connector  5  disposed on a surface of a signal processing substrate  21 , the surface closer to the imaging substrate  20 , are disposed at locations overlapping each other in the vertical direction. The connected cable  40  is housed between the imaging substrate  20  and a holding member  2 . Note that in this structure, the imaging substrate  20  overlaps the signal processing substrate  21 , and therefore the depth dimension of the imaging device is reduced. 
       FIG. 11  illustrates a connecting structure in which a cable  40  is housed in a space S 1  formed by an imaging substrate  20  and a signal processing substrate  21 . According to this structure, it is possible to prevent the cable  40  from coming into contact with a holding member  2 , the imaging substrate  20 , and the signal processing substrate  21 . 
       FIG. 12  illustrates a connecting structure in which the cable insertion direction into a connector  5  on a signal processing substrate  21  is opposite to that in the example illustrated in  FIG. 9 . In addition,  FIG. 13  is a view in which a cable  40  extends from a connector  5 , passes through an insertion hole  6  provided in a signal processing substrate  21 , and is connected to a connector  4 , as compared with the example illustrated in  FIG. 12 . In addition,  FIG. 14  is a view in which a cable  40  extends from a connector  5  disposed on a surface of a signal processing substrate  21 , the surface opposite to the surface of the signal processing substrate  21  closer to an imaging substrate  20 , passes through an insertion hole  6 , and is connected to a connector  4  on the imaging substrate  20 . 
     Various methods for connecting the imaging substrate  20  and the signal processing substrate  21  by the cable  40  are conceivable in addition to the above-described methods. Structures expected to exhibit the above-described effect are not limited to those illustrated here. 
     Embodiments of the present invention have been described above; however, the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, the present invention is not limited to a stereo camera. The present invention may also be applied to a so-called monocular camera including only one imaging element as long as the monocular camera has a structure in which an imaging substrate and a signal processing substrate are connected by a cable. 
     In addition, in the above-described embodiments, the imaging device capable of adjusting the positional relationship between the imaging substrate and the optical system has been described as an example. However, the present invention is effective for an imaging device in which the relative positional relationship between an imaging substrate and an optical system is fixed. This is because workability of connecting a cable to the imaging substrate and a signal processing substrate can be a problem in a case where the imaging device has a structure in which the imaging substrate and the signal processing substrate are connected by the cable. 
     In addition, in the above-described embodiments, the imaging device in which the securing parts to which the cable is connected are the connectors provided on the imaging substrate and the signal processing substrate has been described as an example. However, a securing part is not limited to a connector, and a cable may be secured by soldering or the like. 
     Furthermore, in the above-described embodiments, the imaging device including the securing parts to which the cable is secured and which are provided on the imaging substrate and the signal processing substrate has been described as an example. However, in an imaging device, one of an imaging substrate and a signal processing substrate (for example, the imaging substrate) may be integrated with a cable (or a flexible substrate), and a securing part which secures the cable may be provided only on the other substrate (for example, the signal processing substrate). The present invention is effective even in this case, since workability of adjusting the positional relationship between the imaging substrate and an optical system can be a problem in a case where the imaging device has a structure in which the positional relationship between the imaging substrate and the optical system can be adjusted. 
     REFERENCE SIGNS LIST 
       1  windshield 
       2  holding member 
       3  cover 
       4  connector 
       5  connector 
       6  insertion hole 
       10  imaging element 
       20  imaging substrate 
       21  signal processing substrate 
       30  imaging unit (left imaging unit) 
       31  imaging unit (right imaging unit) 
       32  power supply unit 
       33  video processing unit 
       34  recognition processing unit 
       40  cable 
       50  insulator