Abstract:
The disclosed invention relates to a system for and a method of providing a collision warning to an operator of a vehicle. The disclosed system, which is operable in accordance with the disclosed method, includes a range gated visual imaging means and a processing means. The imaging means is operable to acquire a visual image of an object located within a detection zone whose location relative to the vehicle is known. The processing means is operable to process the image to determine the location of the object relative to the vehicle, determine whether the vehicle might collide with the object, and warn the operator if it is determined that the vehicle might collide with the object.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to a collision warning system and method. In particular, the invention relates to a system for and a method of providing a collision warning to an operator of a vehicle.  
           [0002]    The invention has been developed primarily for alerting an operator of a vehicle such as a rotary or fixed-wing aircraft to the presence of an object such as an electrical power cable or telecommunications infrastructure which may lie in the path of the vehicle and will be described hereinafter with reference to this application, however it will be appreciated that the invention is not limited to this particular use.  
         BRIEF DESCRIPTION OF THE PRIOR ART  
         [0003]    The timely detection of objects which lie in the path of a vehicle such as a helicopter or an aeroplane is critical to the safe operation of such vehicles as it provides the vehicle operator with an opportunity to take appropriate evasive action to prevent a collision occurring between the vehicle and the detected objects.  
           [0004]    Objects which lie in the path of a vehicle can be detected by a person using their sense of sight. Alternatively, artificial means such as radar, sonar, laser radar (lidar) or conventional imaging systems may be used. However, all of these suffer from limitations in their capacity to adequately detect objects.  
           [0005]    For example, when a person&#39;s sense of sight is relied upon, the person may completely fail to detect an object or may only detect an object when it is too late to take evasive action to prevent the vehicle colliding with the object.  
           [0006]    With regard to radar, sonar and laser radar systems, the relatively large amount of time required by these systems to scan an extended area which is proximal to the vehicle limits their ability to detect objects in a timely manner.  
           [0007]    Conventional imaging systems on the other hand are capable of acquiring a large amount of information in a relatively short period of time, however these systems are deficient in a number of respects. For example, the significant amount of time that is often required to process the large amount of information acquired by these systems can prevent the timely detection of objects. Also, the information may not adequately disclose the presence of some objects which lie in the path of a vehicle. Additionally, some conventional imaging systems are unable to detect certain types of objects such as electrical power cables. Further, conventional imaging systems are generally unable to obtain the data that is required to determine the location of an object relative to a vehicle so that a proper assessment of the likelihood of a collision can be made.  
           [0008]    It is an object of the present invention to provide a system for and a method of providing a collision warning to an operator of a vehicle.  
           [0009]    It is a further object of the present invention to overcome, or at least substantially ameliorate, one or more of the deficiencies associated with the prior art.  
           [0010]    Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.  
         SUMMARY OF THE INVENTION  
         [0011]    According to a first aspect of the present invention there is provided a system for providing a collision warning to an operator of a vehicle, the system including a range gated visual imaging means operable to acquire a visual image of an object located within a detection zone whose location relative to the vehicle is known, and a processing means operable to process the image to determine the location of the object relative to the vehicle, determine whether the vehicle might collide with the object, and warn the operator if it is determined that the vehicle might collide with the object.  
           [0012]    The term “visual image” as used herein is to be interpreted as meaning an image which is obtained through the detection of light such as visible, infrared or ultraviolet light, and which may be represented in a visual or non-visual form. For example, in the case of the image being represented in a visual form the image may be displayed as an analogue image on a computer monitor so that a person is able to visually discern the image. In the case of the image being represented in a non-visual form the image may for example be stored in a computer memory as digital data.  
           [0013]    Preferably, the imaging means is operable to either maintain the detection zone at a constant location relative to the vehicle or vary the location of the detection zone relative to the vehicle. The location of the detection zone relative to the vehicle may be varied in response to acceleration or deceleration of the vehicle. In particular, the location of the detection zone relative to the vehicle may be varied such that the detection zone is moved away from the vehicle in response to acceleration of the vehicle, or moved towards the vehicle in response to deceleration of the vehicle. The location of the detection zone relative to the vehicle may be varied in response to manoeuvres which are being or will are to be performed by the vehicle.  
           [0014]    Preferably, the imaging means is operable to vary the size of the detection zone. The size of the detection zone may be proportional to the distance between the vehicle and the detection zone.  
           [0015]    According to a second aspect of the present invention there is provided a method of providing a collision warning to an operator of a vehicle, the method including the steps of:  
           [0016]    (i) operating a range gated visual imaging means to acquire a visual image of an object located within a detection zone whose location relative to the vehicle is known;  
           [0017]    (ii) processing the image to determine the location of the object relative to the vehicle and whether the vehicle might collide with the object; and  
           [0018]    (iii) warning the operator if it is determined that the vehicle might collide with the object.  
           [0019]    Preferably, the location of the detection zone relative to the vehicle is constant or varied. The location of the detection zone relative to the vehicle may be varied in response to acceleration or deceleration of the vehicle. In particular, the location of the detection zone relative to the vehicle may be varied such that the detection zone is moved away from the vehicle in response to acceleration of the vehicle, or moved towards the vehicle in response to deceleration of the vehicle. The location of the detection zone relative to the vehicle may be varied in response to manoeuvres which are being or are to be performed by the vehicle.  
           [0020]    Preferably, the size of the detection zone is varied. The size of the detection zone may be proportional to the distance between the vehicle and the detection zone. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings, in which:  
         [0022]    [0022]FIG. 1 is a block diagram of a collision warning system according to an embodiment of the present invention;  
         [0023]    [0023]FIG. 2 is a conceptual diagram which represents a vehicle carrying the collision warning system illustrated in FIG. 1 and a detection zone which lies in the path of the vehicle and which is imaged by the system;  
         [0024]    [0024]FIG. 3 is a conceptual diagram which is similar to FIG. 2 and which illustrates how a plurality of different detection zones can be sequentially imaged by the collision warning system;  
         [0025]    [0025]FIG. 4 is a conceptual diagram which is similar to FIG. 2 and which illustrates the detection zones imaged by the collision warning system at two different locations of the vehicle; and  
         [0026]    [0026]FIG. 5 is a conceptual diagram which is similar to FIG. 2 and which illustrates the situation where a portion of an electrical power cable is located within a detection zone imaged by the collision warning system at a particular instant in time. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Referring to FIG. 1, a vehicle such as a helicopter or an aeroplane carries a collision warning system  10  having a range gated visual imaging system  11  and a processing system  12 . The collision warning system  10  is operable to rapidly detect objects which lie in the path of the vehicle by repeatedly imaging the space into which the vehicle moves. If the collision warning system  10  determines that a collision is likely to occur between the vehicle and a detected object, the system  10  outputs a timely warning to the vehicle operator so that the operator has sufficient time to take appropriate evasive action to prevent a collision from occurring between the vehicle and the detected object. The collision warning system  10  is able to vary the location and size of the space being imaged so as to vary the timeliness of the warning to suit the speed of travel of the vehicle and manoeuvres which the vehicle is undertaking or may undertake.  
         [0028]    The imaging system  11  includes a light source  13  and a sensor  14 . The imaging system  11  is operable to acquire an image of objects which are located within a predetermined range of distances from the sensor  14  and within a field of view associated with the sensor  14 . The range of distances combined with the field of view of the sensor  14  defines a detection zone whose location relative to the sensor  14  is known by the collision warning system  10 . Since the location of the detection zone relative to the sensor  14  is known it follows that the collision warning system  10  is able to readily determine the location of objects, which appear in an image, relative to the sensor  14 . As the sensor  14  is carried by the vehicle, the location of the objects relative to the sensor  14  corresponds to the location of the objects relative to the vehicle.  
         [0029]    The light source  13  is operated to emit pulses of visible, ultraviolet or infrared light which are directed towards the detection zone. The light pulses may for example be emitted by a conventional light source or, alternatively, by a device such as a laser. In the case of a conventional light source or in the case where the light is infrared, ultraviolet etc. and emitted by a laser, the light pulses are emitted as a broad beam covering the field of view of the sensor  14 . The duration of the light pulses define the required maximum and minimum distances of the range gate of the imaging system  11  and thus, in conjunction with the timing of the gating of the sensor  14 , the detection zone imaged by the sensor  14 .  
         [0030]    The sensor  14  is in the form of a light sensor which is primarily sensitive to light emitted by the light source  13 . The sensor  14  may, for example, be a camera. The sensor  14  is operated to detect light emitted from the light source  13  which is reflected towards the sensor  14  from an object located within the detection zone. The aforementioned operation of the sensor  14  includes enabling or gating the sensor  14  to detect light for a short period of time after each light pulse is emitted by the light source  13 . The gating of sensor  14  is delayed for a short period of time after each pulse of light is emitted by the light source  13 . The length of the delay is approximately equal to the time required for a pulse of emitted light to travel from the light source  13  to the detection zone and for a portion of the emitted light that is reflected towards the sensor  14  from an object located within the detection zone to reach the sensor  14 . The time delay in gating the sensor  14  enables the distance between the detection zone and the sensor  14 , and therefore the distance between the sensor  14  and an object contained within the detection zone, to be calculated. The distance between the sensor  14  and the detection zone is calculated as the speed of light divided by the time delay. The duration of time for which the sensor  14  is gated is such that the portion of an emitted light pulse that is reflected from within the detection zone and received by the sensor  14  will dominate the image acquired by the imaging system  11 .  
         [0031]    The imaging system  11  can vary the distance between the detection zone and the sensor  14  by changing the duration of the time delay prior to gating the sensor  14 . Thus, by reducing the time delay the detection zone is brought closer to the sensor  14 , while increasing the time delay has the effect of moving the detection zone further away from the sensor  14 .  
         [0032]    The imaging system  11  can also vary the size of the detection zone by changing the duration of the time delay prior to gating the sensor  14 , changing the duration of time for which the sensor  14  is gated, or changing the field of view of the sensor  14 .  
         [0033]    The operation of the optical range gated visual imaging system  11  will not be discussed any further as such systems and their operation are well known in the art.  
         [0034]    The processing system  12  includes a storage device  15 , a processor  16  and an output means  17 . The processing system  12  processes images which are acquired by the imaging system  11  together with other data associated with the vehicle which carries the collision warning system  10 . This other data may relate to the speed of the vehicle and the manoeuvring capabilities of the vehicle. In particular the processing system  12  processes the images to detect objects which appear in the images and to determine their location relative to the vehicle. The processing system  12  also determines the likelihood of the vehicle colliding with the detected objects. If the processing system  12  determines that the vehicle is likely to collide with an object, a suitable warning signal is output from the output means  17 .  
         [0035]    The storage device  15  is used to store the image data acquired by the imaging system  12  and the vehicle data.  
         [0036]    A program, which is executed by the processor  16 , processes the image and vehicle data which is stored on the storage device  15 . The program uses a suitable algorithm such as the Hough transform to detect and characterise linear objects such as electrical power cables and telecommunications infrastructure such as antenna towers which may appear in the image. The program then determines the locations of the detected objects and the likelihood of the vehicle colliding with the objects. If the program determines that a collision is likely to occur between the vehicle and a detected object, the program causes a suitable warning signal to be output from the output means  17 . The warning signal may include information relating to the location and extent of the detected objects relative to the vehicle. The warning signal from the output means  17  is presented to the vehicle operator, which may for example be a person or an automated vehicle controlling system such as an autopilot. In the case where the warning signal is output to an autonomous vehicle controlling system, the warning signal alerts the autonomous vehicle controlling system to the need for evasive action. The timing of the warning signal is such that there is sufficient time for the vehicle operator to act upon the warning signal so that a collision is avoided.  
         [0037]    The collision warning system  10  is able to adjust the size and location of the detection zone relative to the sensor  14  (and therefore the vehicle) in response to changes in the vehicle speed or manoeuvres which the vehicle is undertaking or may undertake. This enables the collision warning system  10  to provide adequate warning of a likely collision under a range of circumstances. For example, in the case where the speed of the vehicle changes or the nature of the manoeuvres undertaken by the vehicle change, the collision warning system  10  suitably adjusts the size and location of the detection zone relative to the sensor  14  to ensure that the vehicle operator will have sufficient time to take evasive action and prevent a collision from occurring should a warning signal be generated. Thus, the detection zone may for example be moved away from the vehicle in response to acceleration of the vehicle, and moved towards the vehicle in response to deceleration of the vehicle. Also, if it is known that the vehicle requires a certain amount of space in which to manoeuvre, the size and location of the detection zone can be adjusted so that the imaging system  11  is able to acquire an image of the space into which the vehicle may manoeuvre. In this way, the system  10  is able to maintain a map of all areas into which the vehicle may manoeuvre.  
         [0038]    Either prior to or during the commencement of motion of the vehicle the collision warning system  10  acquires a three-dimensional image of a detection zone into which the vehicle will initially move and stores the image in the storage device  15 . The processor  16  then processes the stored image to detect any objects which might appear in the image. The processor  16  then determines the location of any detected objects relative to the vehicle and the likelihood of a collision occurring between the vehicle and the detected objects. A warning signal is output from the output means  17  if the system  10  determines that a collision between the vehicle and a detected object is likely to occur.  
         [0039]    As the vehicle moves, the system  10  acquires an image from a further detection zone which is located beyond the initial detection zone such that the further detection zone overlaps with the initial detection zone. The processor  16  then processes the images acquired from the further detection zone in the same manner as the image from the initial detection zone. Data relating to a detection zone through which the vehicle has passed or which the vehicle is unable to pass through is deleted from the storage device  15 . The various steps commencing with the acquisition of an image from a detection zone through to the deletion of data from the storage device  15  are repeated.  
         [0040]    Referring to FIG. 2, a vehicle  20  carrying the collision warning system  10  moves in a direction indicated by arrow A. At a particular instant of time, the system  10  acquires an image from a detection zone  21 , which lies in the path of the vehicle  20 , and stores the acquired image in the storage device  15 . The detection zone  21  is roughly defined by the volume bounded by the field of view (indicated by lines F) of the sensor  14  and two spaced curved surfaces S 1  and S 2  whose centres of curvature coincide with the location of the sensor  14 . The curved surfaces S 1  and S 2  define a range of distances from the sensor  14 . The processing system  12  processes the image acquired by the imaging system  11  together with other data associated with the vehicle  20  such as the speed of the vehicle  20  and the manoeuvring capabilities of the vehicle  20 . If the processing system  12  determines that there is a likelihood of a collision occurring between the vehicle  20  and any detected objects, the processing system  12  outputs a suitable warning signal from the output means  17 . The timing of the warning signal is such that the vehicle operator has sufficient time to act upon the warning signal so as to avoid a collision occurring between the vehicle  20  and the detected objects. As the vehicle  20  moves, the collision warning system  10  repeats the above process. It is preferred that the further detection zones overlap each other, however the detection zones may be adjacent to each other.  
         [0041]    Referring to FIG. 3, the vehicle  20  is about to or has just commenced motion in the direction indicated by arrow A. Either prior to or during the commencement of motion of the vehicle  20  the system  10  initially acquires images from a detection zone which includes a plurality of smaller detection zones (such as detection zones  22  and  23 ) located at various distances and within a specified maximum distance from the vehicle  20 . The system  10  stores the images acquired from the various smaller detection zones in the storage device  15 . The acquired images provide the vehicle operator with an initial map of objects which may lie in the path of the vehicle  20 . If the system  10  acquires the images during the commencement of motion of the vehicle  20 , the detection zone which is closest to the vehicle  20  is imaged prior to those detection zones which are located further away from the vehicle  20 . For example, the system  10  will image detection zone  22  before detection zone  23 . Although not illustrated, there are intervening detection zones between the vehicle  20  and the detection zones  22 ,  23 . Once the initial map has been acquired by the system  10  and the vehicle  20  begins to move, the imaging system  12  begins acquiring images from further detection zones which lie in the path of travel of the vehicle  20 . Images from the further detection zones are stored in the storage device  15 . Alternatively, the system  10  may continue to acquire images from a plurality of detection zones located at various distances and within a specified maximum distance from the vehicle  20 . If the processing system  12  determines that a collision is likely to occur between the vehicle  20  and a detected object, the processing system  12  outputs a timely warning signal from the output means  17 .  
         [0042]    Referring to FIG. 4, the vehicle  20  is moving in the direction indicated by arrow A and is displaced by a distance D from the location where the system  10  acquired an image from a detection zone  24 . Following the displacement of the vehicle  20  by the distance D the system  10  acquires a new image from a detection zone  25 , which is also displaced from the previous detection zone  24  by the distance D, and stores the new image in the storage device  15 . The distance D is equal to the distance between the spherical surfaces which bound detection zone  24  so that detection zone  25  is adjacent to detection zone  24 . However, the distance D may be such that the detection zones  24  and  25  overlap or are spaced apart. If the processing system  12  determines that a collision is likely to occur between the vehicle  20  and a detected object, the processing system  12  outputs a timely warning signal from the output means  17 . The system  10  continues to acquire images from further detection zones as the vehicle  20  moves.  
         [0043]    In FIG. 5, the vehicle  20  moves in the direction indicated by arrow A and the collision warning system  10  acquires an image from a detection zone  26  within which an electrical power cable  30  is located. The processing system  12  processes the image acquired by the imaging system  11  and determines the likelihood that the vehicle  20  will collide with the cable  30 . If the processing system  12  determines that the vehicle  20  is likely to collide with the cable  30 , the processing system  12  outputs a timely warning signal from the output means  17 .  
         [0044]    The foregoing describes only one embodiment of the present invention, and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.  
         [0045]    For example, a different algorithm to the Hough transform may be used to detect objects which appear in images acquired by the imaging system  11 .