Abstract:
A vehicular vision system includes a plurality of cameras mounted at a vehicle, with each camera including a respective image sensor and having a respective field of view exterior of the vehicle. The system includes a control and a video output for transmitting a stream of video captured by an image sensor of a camera of the plurality of cameras, and a serial data interface permitting a microcontroller of the control to communicate with at least one electronic device of the vehicle. A switch is openable by the microcontroller to deactivate the video output and closable by the microcontroller to activate the video output. The microcontroller complies with messages received via a serial data bus. The control sends instructions to a camera of the plurality of cameras via the serial data bus and the control receives messages from an electronic device of the vehicle via the serial data bus.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 13/964,138, filed Aug. 12, 2013, now U.S. Pat. No. 8,941,480, which is a continuation of U.S. patent application Ser. No. 12/992,301, filed Nov. 12, 2010, now U.S. Pat. No. 8,508,350, which is a 371 national phase entry of PCT Application No. PCT/US2009/044111, filed May 15, 2009, which claims the filing benefits of U.S. provisional application Ser. No. 61/053,705, filed May 16, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention generally relates to a vehicular system for displaying video input from a plurality of video sources, and more particularly, to an automotive camera system comprising two or more cameras sharing a common display. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is known to provide a rearward facing camera or imaging sensor or device at a rear of a vehicle and with a generally rearward and downward field of view to capture images of the area immediately rearward of the vehicle for a rear vision system or back up aid system or the like. Examples of such rear vision devices and systems are described in U.S. Pat. Nos. 7,005,974; 6,989,736; 6,757,109; 6,717,610; 6,396,397; 6,201,642; 6,353,392; 6,313,454; 5,550,677; 5,670,935; 5,796,094; 5,877,897; 6,097,023 and 6,498,620, and PCT Publication No. WO 2004/047421, which are all hereby incorporated herein by reference in their entireties. 
         [0004]    For parking into parallel parking spots along a street it is also known to provide a camera mounted on the passenger side of the vehicle, facing generally rearward and to the side, thereby providing the driver a better view of the curb and other objects to the side of the vehicle. 
         [0005]    To connect two or more video sources to the same display video switches are often used to toggle between the alternative video sources. An example of an in-vehicle video architecture using video switching is illustrated in U.S. Pat. No. 7,050,089, which is incorporated hereby by reference in its entirety. Video switches may be stand alone control units or integrated with other control units, e.g., a display device. 
         [0006]    While a video switch is useful to share one display between two or more cameras it adds significant cost. Therefore, it is desirable to share one display device between two or more cameras without the need for a video switch. 
       SUMMARY OF THE INVENTION 
       [0007]    In one aspect, the invention is directed to a system for providing and displaying video information in a vehicle. The system includes a display device having a video input, a plurality of video sources each having a video output, wherein the video outputs from the video sources are connected in parallel to the video input of the display device, and a video source control device configured to keep no more than one video source activated at a time when the display is active. 
         [0008]    In a particular embodiment, one or more of the video sources may be a camera. For example, one of the video sources may be a rear-mounted rearview camera on the vehicle. As another example, one of the video sources may be a camera mounted at the side of the vehicle to provide a view of a curb during parking of the vehicle. 
         [0009]    The video source control device is configured to control the activation and deactivation of the video sources. The video source control device may further be configured to control the activation and deactivation of the display device. The video source control device may communicate with the video sources through a serial data bus that is suitable for vehicular use, to instruct the video sources to activate or deactivate as desired. 
         [0010]    In another aspect, the invention is directed to a camera for a vehicle. 
         [0011]    The camera includes an image sensor, a microcontroller and a serial data interface. 
         [0012]    The image sensor has an image sensor video output configured for transmitting a stream of video captured by the image sensor to a camera video output connector. The image sensor video output includes a video plus electrical conduit and a video minus electrical conduit. The microcontroller is operatively connected to the image sensor. The serial data interface permits the microcontroller to communicate with at least one other electronic control module in the vehicle. A resistor having a selected impedance connected in series with a switch are provided, wherein the resistor and switch connect the video plus electrical conduit and the video minus electrical conduit. The switch is openable by the microcontroller to deactivate the image sensor video output into a high impedance state and is closable to activate the image sensor video output. The microcontroller is configured to comply with a selected message received from another electronic control module in the vehicle through the serial data interface by opening the switch. 
         [0013]    In yet another aspect, the invention is directed to a method for switching between a plurality of video sources in a vehicle, wherein the video sources are connected to a display device in parallel, including one activated video source and at least one deactivated video source, comprising: a) deactivating the activated video source; and b) activating one deactivated video source. 
         [0014]    In yet another aspect, the invention is directed to a method for switching between a plurality of video sources in a vehicle, wherein the video sources are connected to a display device in parallel, including one activated video source and at least one deactivated video source, comprising: a) deactivating the display device; b) deactivating the activated video source; c) activating one deactivated video source after at least one of steps a) and b); and d) activating the video display device. 
         [0015]    In yet another aspect, the invention is directed to a video selection system, including a plurality of video sources, each having a video output, a video selector switch configured to selectively provide a connection between any selected one of the video sources and a video input of a display device, a video source control device operatively connected to the video sources and to the video selector switch, such that the video source control device is configured to control which video source is connected to the display device, and is configured to permit no more than one video source to be active at any given time when the display device is active. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a block diagram of a camera used in one aspect of the invention. 
           [0017]      FIG. 2  is a more detailed illustration of the video conditioning block of  FIG. 1  when used in a single-ended configuration. 
           [0018]      FIG. 3  is a more detailed illustration of the video conditioning block of  FIG. 1  when used in a differential video configuration. 
           [0019]      FIG. 4  is a more detailed illustration of the video conditioning block of  FIG. 1  when used in a single-ended video configuration with variable resistance. 
           [0020]      FIG. 5  is a more detailed illustration of the video conditioning block of  FIG. 1  when used in a differential video configuration with variable resistance. 
           [0021]      FIG. 6  is a block diagram showing an exemplary vehicle camera system with two cameras, a display device and a camera control device. 
           [0022]      FIG. 7  is a block diagram showing an exemplary video system with four video sources, a display device and a video selector device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Reference is made to  FIG. 6 , which shows a schematic illustration of a system  10  for displaying video input from a plurality of video sources for use in a vehicle, in accordance with an embodiment of the present invention. The system  10  shown in  FIG. 6  includes a plurality of video sources  11  which are connected in parallel to a common display device  14 . The video sources  11  may each be any suitable source of video signals such as a camera (e.g., a rear-mounted rearview camera or a side-mounted rearview camera), a DVD player, a vehicular navigation system or a connection to an external, user-supplied, electronic device. In the embodiment shown in  FIG. 6 , two cameras  12 , shown individually at  12   a  and  12   b,  make up the plurality of video sources. The first camera  12   a  may, for example, be mounted at the rear of a vehicle, and the second camera  12   b  may be mounted at the side of the vehicle. 
         [0024]    The cameras  12  are wired in parallel to a common video input shown at  16  of the display device  14 . The cameras  12  are configured such that their video output shown at  17  (and shown individually at  17   a  on the first camera  12   a  and at  17   b  on the second camera  12   b ) can be activated and deactivated in response to an instruction from a video source control device  18 , which may be referred to as a camera control device  18  in the embodiment shown in  FIG. 6  wherein all the video sources  11  are cameras  12 . The video output  17  may be referred to as the camera video output. 
         [0025]    The camera control device  18  communicates with the cameras  12  through a serial data bus  20 . The camera control device  18  activates no more than one camera  12  at any given time and deactivates any other cameras  12  in the system  10 . In this way, the central camera control device  18  acts as a central arbitration logic, controlling which camera  12  gets access to the display device  14  at any given time. 
         [0026]    The central camera control device  18  may select which camera  12  is active based on interaction with a user. For example, a switch or reconfigurable menu may be provided in the vehicle cabin that is usable by the vehicle driver to select which camera  12  to activate. The central camera control device  18  may also automatically select which camera  12  to activate based on data received from other control units within the vehicle, such as control units that indicate gear position, steering angle, parking spot orientation information from a navigation system, or situational analysis information derived from an image processing system, a radar sensor system, an ultrasonic ranging system or a LIDAR sensor system. 
         [0027]    Optionally, the display device  14  may be configured to prevent the appearance of undesirable artifacts when switching between two cameras  12 . The switching the video to be displayed from one camera  12  to another camera  12  (e.g., from the first camera  12   a  to the second camera  12   b ) may be carried out using the following method: The camera control device  18  temporarily deactivates the display device  14 . For example, the camera control device  18  may command the display device  14  to show a blank screen. While the display device  14  is deactivated any video data or video artifacts at its input are ignored and not visible to the user of the vehicle. Next, the camera control device  18  sends a first serial data message along serial data bus  20  to the first, presently active, camera  12   a , instructing the first camera to deactivate its output. Responsive to the first serial data message the first camera deactivates its output  17   a.  The camera control device  18  also sends a second serial data message along the serial data bus  20  to the second, presently deactivated camera  12   b.  Responsive to the second serial data message the second camera  12   b  starts producing video. Lastly, the camera control device reactivates the display device  14  to show the video received at its video input  16 . 
         [0028]    The above-described method need not be executed in the precise order of steps described. For example, the camera control device  18  may send the instruction to deactivate to the first camera  12   a  before it deactivates the display device  14 . 
         [0029]    It will also be noted that, in embodiments wherein the display device  14  is deactivated as a first step, the activated camera need not be deactivated prior to the activation of a deactivated camera. This is because crosstalk between two activated cameras  12  is permissible when the display device  14  is deactivated. As a result, in embodiments wherein the display device  14  is deactivated as a first step, the camera control device  18  need not keep only one camera  12  active at any given time. Instead the camera control device  18  keeps only one camera  12  active at any given time when the display device  14  is activated. 
         [0030]    The above-described method prevents the appearance of undesirable artifacts when switching between two cameras  12 . It will be understood that the deactivation and subsequent activation of the display device  14  is optional and that it is possible to practice a method of switching between cameras  12  that are connected in parallel to a display device in a vehicle by: deactivating an active camera; and activating a deactivated camera, so that only one camera is activated at any given time. 
         [0031]    Referring to  FIG. 1 , the cameras  12  used within the system  10  may each comprise a lens  23 , an image sensor  24  for receiving images from the lens  23 , such as a CMOS image sensor, a video conditioning element  26 , an oscillator  28 , a power supply  30 , a microcontroller  32 , a connector  34  for connecting to an electrical power source within the vehicle, a ground connector  35  for connecting to ground, a serial data interface  36  including a transceiver  36   a  and an associated connector  36   b  for communicating via serial data bus with another component, such as the camera control device  18  ( FIG. 6 ), and the video output  17 . In the embodiment shown in  FIG. 1 , the serial data interface  36  is a CAN interface, however the serial data interface may be any other suitable type of interface known in the art for communicating on any other suitable bus known in the art, such as for example, LIN, Flexray, MOST, or Ethernet. 
         [0032]    When the camera control device  18  ( FIG. 6 ) deactivates or activates the camera, it may do so by sending instructions to the microcontroller  32  through the serial data interface  36 . The microcontroller  32  then controls the internal components of the camera  12  as needed to carry out the deactivation or activation. 
         [0033]    The camera  12  communicates with the display device  14  through the video output  17 . The video output  17  provides a composite video signal, which may be provided according to any suitable format, such as an NTSC standard format. 
         [0034]    The image sensor  24  has an image sensor video output shown at  40  which is made up of a video plus electrical conduit  41  (which may be referred to as a video plus line) and a video minus electrical conduit  42  (which may be referred to as a video minus line). The image sensor video output  40  passes through the video conditioning element  26  to the camera video output  17 . 
         [0035]    In an embodiment shown in  FIG. 2 , the video conditioning element  26  comprises a 150 Ohm resistor  43  between the video plus line  41  and the video minus line  42 , and a ground connection shown at  44  connected to the video minus line  42 . When two cameras  12  thus equipped are arranged in parallel, as shown in  FIG. 2  the cameras  12  have a parallel resistance of 75 Ohms, thereby complying with the standard impedance used in 1 Vpp NTSC composite video outputs in automotive applications. 
         [0036]    In another configuration shown in  FIG. 3 , the video conditioning element  26  may comprise a differential video output, wherein each output line  41  and  42  is connected through an individual 75 Ohm resistor  46  to ground, so that the resistance between the two output lines  41  and  42  is 150 Ohm. Thus, the parallel resistance of two cameras  12   a  and  12   b  in the configuration shown in  FIG. 3  is 75 Ohm. 
         [0037]    Depending on the wiring harness configuration in a particular vehicle it may be desirable to use an asymmetrical resistance distribution between two or more cameras  12  to minimize noise coupled into the video feed from the cameras  12  to the display device  14 . The resistance of each parallel camera  12  may be selected as desired, while providing a parallel resistance for all cameras  12  of around 75 Ohms. In other words, the resistance in the cameras  12  need not be the same. Each camera  12  may have an individually selected resistance that may or may not be the same as the resistance in any other camera  12  in the system  10 , while keeping the overall parallel resistance at or about 75 Ohms. 
         [0038]    In another configuration, shown in  FIG. 4 , a switch  48  may be provided in series with a 75 Ohm resistor  50  between the output lines  41  and  42 . When the camera control device  18  ( FIG. 6 ) instructs a camera  12  to deactivate itself, one of the steps carried out by the microcontroller  32  is to open the switch  48 , thereby switching the image sensor video output  40  into a state of very high impedance (e.g., several kilo-Ohms). When the camera control device  18  instructs a camera to activate itself, one of the steps carried out by the microcontroller  32  is to close the switch  48  so that the image sensor video output  40  has a selected operating impedance, such as, for example 75 Ohms. The cameras  12  in parallel include one camera  12  (e.g., camera  12   a ) that is active and that therefore has an output impedance of 75 Ohms, and a camera  12  (e.g., the camera  12   b ) which has an impedance of several kilo-Ohms, so that the parallel resistance of the cameras  12  to be around the 75 Ohms standard. 
         [0039]    More specifically the camera control device  18  causes the switch  48  on one camera  12  (e.g., camera  12   a ), thereby activating that camera, and opens the switch  48  on the other camera  12  (e.g., camera  12   b ) thereby deactivating the other camera. The active camera  12   a  therefore has an output impedance of 75 Ohms, while the other camera  12   b  has a very high output impedance of several kilo-Ohms, so that the parallel resistance of the cameras  12  to be around the 75 Ohms standard. When it is desired to display video from the second camera  12   b  on the display device  14 , the camera control device  18  opens the switch  48  on the first camera  12   a  and closes the switch on the second camera  12   b.    
         [0040]    The configuration shown in  FIG. 5  may be similar to the configuration shown in  FIG. 4 , except that the configuration shown in  FIG. 5  provides a differential output, whereas the output in the configuration in  FIG. 4  is single-ended. Thus, the configuration shown in  FIG. 5  does not include a ground connection to the video minus line  42 . 
         [0041]    In the embodiments shown in  FIGS. 2-6 , two video sources  11  (i.e., two cameras  12 ) are shown as part of the system  10 . It will be noted, however, that any suitable number of video sources  11  may be included in the system  10 . The specific resistance used in each camera, particularly in the embodiments shown in  FIGS. 2 and 3  may be selected based on the overall number of video sources  11  connected in parallel so that a selected parallel resistance (e.g., 75 Ohms) is provided. 
         [0042]    The display device  14  may be any suitable type of display device, such as a dashboard-mounted liquid-crystal display positioned to be viewed by the vehicle driver. Optionally a touch-screen interface or any other user interface may be included on the display device  14 . 
         [0043]    Reference is made to  FIG. 7 , which shows a system  100  for providing and displaying video information in a vehicle, in accordance with another embodiment of the present invention. In the system  100  a plurality of video sources  11  (shown individually at  11   a,    11   b,    11   c  and  11   d ) are controlled by a video source control device  18  and are connected at their outputs  17   a,    17   b,    17   c  and  17   d  to four inputs  101  (shown individually at  101   a,    101   b,    101   c  and  101   d ) of a video selector switch  102  which is itself connected at its output  106  to the input  16  of the video display device  14 . The video source control device  18  controls the operation of the video sources  11  through the serial data network  20  and also controls the operation of the video selector switch  54 . As in the embodiments shown in  FIGS. 2-6 , the video source control device  18  activates one video source  11  at a time while keeping all other video sources  11  deactivated. 
         [0044]    In an exemplary embodiment, a method used to change the active video source from video source  11   a  to video source  11   c  includes the following steps: The camera control device  18  temporarily deactivates the display device  14 . The video source control device  18  deactivates the activated video source  11   a.  The video source control device  18  then moves the video selector switch to connect the video source  11   c  to the display device  14 . The video source control device  18  then activates the video source  11   c.  The camera control device  18  reactivates the display device  14  to show the video received from the video source  11   c.    
         [0045]    It will be noted that the video source control device  18  may reactivate the display device  14  prior to activating the video source  11   c.  Additionally, the control device  18  may deactivate the activated video source  11   a  prior to deactivating the display device  14 . 
         [0046]    Because only one video source  11  is producing video at any given time the video selector switch  102  may be a simple electromechanical relay or other relatively inexpensive switching device, without requiring any precaution for preventing crosstalk between its inputs. 
         [0047]    With respect to any of the above described embodiments, there may be some small time overlap during the deactivation of an active video source and the activation of a deactivated video source. Such a time overlap may last for several milliseconds. In such embodiments, however, the video source control device  18  is nonetheless considered to keep only one video source active at a given time and to hold all other video sources deactivated. 
         [0048]    While the present invention has been described with reference to exemplary embodiments, it will be readily apparent to those skilled in the art that the invention is not limited to the disclosed or illustrated embodiments but, on the contrary, is intended to cover numerous other modifications, substitutions, variations and broad equivalent arrangements that are included within the spirit and scope of the following claims.