Abstract:
In a night vision arrangement for a motor vehicle in which a camera captures an infra-red image of the roadway in front of the vehicle, a video signal generated by the camera is processed by a signal processor so that the field of view of the image displayed by a display unit is selected in accordance with a control signal. The control signal is generated by a signal generator which is responsive to one or more parameters of the movement of the vehicle. The width of the field of view may be decreased with increasing speed. The axial direction of the field of view may be adjusted depending upon the nature of a turning movement of the vehicle.

Description:
RELATED APPLICATIONS 
     This application is a continuation application from co-pending U.S. application Ser. No. 10/753,191, which in turn, was a continuation application of an International Application No. PCT/SE01/02283 entitled “A Night Vision Device for a Vehicle.” Both applications are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     THE PRESENT INVENTION relates to a night vision device for a vehicle such as a motor vehicle. 
     2. Description of Related Art 
     It has been proposed previously to provide a night vision device in a vehicle such as an automobile. The purpose of the night vision device is to enhance the vision of the driver in night conditions. 
     Various night vision devices have been proposed before. U.S. Pat. No. 5,414,439 describes a night vision arrangement which utilises a “head-up” display. A motor vehicle is provided with an infra-red camera positioned to view the roadway in front of the vehicle. The camera generates a video signal which is passed to a “head-up” display of the type utilised in combat aircraft. In the embodiment described, the windshield of the motor vehicle or a semi-transmitter is utilised as a combiner to combine the image of the road ahead, as viewed through the windshield by the driver, and a virtual image of the road ahead from an image generator which receives the video signal from the camera. 
     In U.S. Pat. No. 5,414,439 the infra-red camera is mounted in a fixed position to provide an image of the view in the front of the vehicle. Also the camera has a fixed focal length. Consequently, when cornering the vehicle, that is to say when turning the vehicle to the right or to the left, the camera will always point in a direction aligned with the longitudinal axis of the vehicle. However, there is a need for the driver of the vehicle to view the environment into which the vehicle is moving which will be located either to the left or to the right of the fixed field of view of the camera. 
     JP-A-0 6048247 discloses a vehicle mounted infra-red image display arrangement, and in this arrangement the precise field of view that is displayed to the driver of the vehicle is dependent upon the position of the front or steering wheels of the vehicle. However, even in an arrangement such as this, it is difficult to ensure that the appropriate image is displayed, since the field of view that is of interest to the driver is not necessarily aligned with the rolling direction of the steering wheels of the vehicle. 
     When a motor vehicle is being driven quickly, the driver of the vehicle tends to concentrate on the road ahead of the vehicle, but, in contrast, when the vehicle is travelling slowly, for example in a built-up area, the driver usually pays attention to situations that may develop on either side of the roadway. Thus the driver may be particularly conscious of pedestrians who are not in the roadway, but who may step into the roadway in front of the vehicle. Thus, when a driver is driving quickly, the driver tends to concentrate on a relatively narrow angular field of view, whereas when the vehicle is driving more slowly, the driver tends to concentrate on a wider angular field of view. If the image provided by a night vision arrangement of the type discussed above were to be utilised to provide the wide field of view, whilst providing a sufficiently large image of the road ahead for fast driving, with a fixed focal length of the lens of the infra-red camera, a very wide display would have to be provided, which may prove to be impractical in many vehicle installations. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide an improved night vision arrangement. 
     According to one aspect of this invention there is provided a night vision arrangement for a vehicle, the night vision arrangement including an infra-red-sensitive camera fixed to the motor vehicle to capture an image of the roadway in front of the vehicle, the image having a predetermined horizontal angular field of view, the camera generating a video signal representing the image, the arrangement further including a display unit adapted to display at least part of the captured image to the driver of the vehicle, characterised in that the arrangement further comprises a signal processing unit adapted to process the video signal, and a sensor unit adapted to sense one or more parameters of the movement of the vehicle, and to provide a control signal, the arrangement being such that, in use, the signal processor electronically processes the video signal so that the field of view of the image displayed by the display unit is selected in accordance with the said control signal. 
     Preferably the signal processor is adapted to process the video signal so that the angular extent of the field of view of the image displayed by the display unit is related to the speed of the vehicle, the sensor being adapted to sense speed. 
     According to another aspect of this invention there is provided a night vision arrangement for a vehicle, the night vision arrangement including an infra-red-sensitive camera fixed to the motor vehicle to capture an image of the roadway in front of the vehicle, the image having a predetermined horizontal angular field of view, the camera generating a video signal representing the image, the arrangement further including a display unit adapted to display at least part of the captured image to the drive of the vehicle, characterised in that the arrangement further comprises a sensor unit adapted to sense the speed of the vehicle and to generate a control signal, the control signal controlling an arrangement which is operative so that the angular extent of the field of view of the image displayed by the display unit is related to the speed of the vehicle. 
     In one embodiment the arrangement comprises a signal processing unit adapted to process the video signal, the signal processor being connected to process electronically the video signal so that the angular extent of the field of view of the image displayed by the display unit is related to the speed of the vehicle. 
     In another embodiment the arrangement further comprises an adjustable optical system provided on the camera, the control signal being adapted to control the adjustable optical system on the camera so that the angular extent of the field of view of the image displayed by the display unit is related to the speed of the vehicle. 
     Preferably part of the image captured by the camera is selected for display, that part being selected in dependence upon the direction of movement of the vehicle, the sensor being adapted to sense the direction of movement of the vehicle. 
     Conveniently the sensor includes means to sense the rolling direction of the steering wheel relative to the vehicle. 
     Advantageously the sensor senses the instantaneous position of the vehicle in a co-ordinate system to derive a signal corresponding to the driving direction and/or speed of the vehicle. 
     Preferably the means for sensing the instantaneous position of the vehicle incorporate a GPS sensor arrangement. 
     Conveniently the display unit is a monitor which displays an image directly to the vehicle operator. 
     Alternatively the display unit is a head-up display unit. 
     Preferably the head-up display unit incorporates a mirror for reflecting a virtual image to the driver of the vehicle. 
     Conveniently the mirror is a semi-transparent mirror, enabling the operator to view the reflected image and, simultaneously, to see a real image through the mirror. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a block schematic view of one embodiment of the invention, 
         FIG. 2  is a corresponding block schematic view of a second embodiment of the invention, 
         FIG. 3  is a diagrammatic plan view of a vehicle provided with a night vision arrangement in accordance with the invention, 
         FIG. 4  is a diagrammatic view of a display provided on the vehicle of  FIG. 3  in one condition, 
         FIG. 5  is a view corresponding to  FIG. 4  illustrating the display in another condition, 
         FIG. 6  is a diagrammatic view, corresponding to  FIG. 3 , of a vehicle provided with another system in accordance with the invention, and 
         FIG. 7  is a view, corresponding to  FIG. 4 , showing the display of the embodiment of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1  of the accompanying drawings, a night vision system for a motor vehicle comprises a camera  1 , a signal processing arrangement and a display unit  3 . 
     The camera  1  is provided with a lens  5 . The front face of the lens is dome-shaped, and the front face of the lens is provided with a hard coating of micro-sized diamond. The dome-shape of the lens tends to facilitate cleaning of the lens by wind as the vehicle on which the camera is mounted moves. Located behind the lens  5 , in alignment with the optical axis of the lens, is a beam deflector  6  which is constituted by an inclined mirror  7 . The beam deflector is provided in a hollow tubular neck  8 , which contains a focusing lens  10  which may be adjusted by means of a focusing ring (not shown). The neck  8  is connected to a lower housing  9 . The housing  9  contains an infra-red sensor element  11 , which may be a charge-coupled sensor element, which is mounted on an electronic unit  12 . 
     It is to be appreciated, therefore, that in use of the camera  1 , the camera will be positioned so that the image viewed by the lens  5  is an image of the roadway in front of the vehicle. The image, after being deflected by the beam deflector  6 , is focussed, by the focusing lens  10 , on to the planar infra-red sensor  11 . The focus, and thus the field of view, of the camera may be adjusted by adjusting the focusing ring to provide an “optical zoom” effect in response to a central signal from the sensor  4 . 
     The camera  1  provides a video output signal on an output lead  13 . The output lead  13  is connected to a signal processor  2  forming part of the signal processor arrangement. The signal processor  2  is connected to receive an input control signal from a sensor unit  4 . The sensor unit  4  may be simply a speed sensor adapted to sense the speed of the vehicle. The speed sensor may be connected to the speedometer of the vehicle, or may be connected to a wheel speed sensor forming part of an ABS system. Alternatively, the sensor  4  may be responsive to the position of the front or steering wheels of the vehicle, or an element associated with the steering wheels of the vehicle, such as a tie rod or the steering wheel shaft. Alternatively again, the sensor  4  may be a sensor which can sense the instantaneous position of the vehicle in a co-ordinate system, thus providing signals corresponding to the instantaneous speed and driving direction of the vehicle. Thus, for example, the sensor  4  may be a GPS (Global Positioning System) sensor. The GPS system utilises signals from a number of geo-stationary satellites which transmit accurate timing systems. A GPS sensor processes the signals that it receives from the satellites and can provide very accurate indications as to the position of the sensor. Thus it is envisaged that the sensor  4  may incorporate a GPS sensor to process signals received from the satellite system to determine the position of the vehicle, with the sensor  4  including a processor to determine successive positions of the vehicle and to determine the instantaneous speed and driving direction of the vehicle. 
     It is thus to be appreciated that the sensor  4  may include one or more sensors of the types generally discussed above, and the sensor  4  will provide a control signal as an input to the signal processor  2 , that input being indicative of the speed of the vehicle and/or the direction of driving of the vehicle. 
     The signal processor unit has an output  14  which is connected to an image generator  15  forming part of the display unit  3 . The image generator  15  may be a cathode-ray device, or any other conventional form of image generator. The image generator  15  is positioned appropriately with regard to a semi-silvered aspherical mirror  16  which forms part of a conventional head-up display unit. The mirror  16  may be mounted on, or may form part of the windshield of a vehicle and may be positioned so that the virtual image that is displayed on the minor  16 , from the image generator  15 , as viewed by the driver of the vehicle, is super-imposed on the ordinary view of the roadway in front of the vehicle enjoyed by the driver of the vehicle. 
     As will be described below, in embodiments of the invention, the signal processor  2  processes the signal received from the camera  1 , so that the image displayed by the display unit  3  is appropriate, taking into account the speed and/or direction of driving of the vehicle. 
       FIG. 2  illustrates an alternative embodiment of the invention. The camera  1  and the signal processing unit  2  are as described above with regard to  FIG. 1 , and thus these parts of the system will not be re-described. 
     In the embodiment of  FIG. 2 , instead of a head-up display unit as described in  FIG. 1 , a simple monitor or visual display unit  19  is provided, which displays the image obtained from the camera as processed by the signal processing unit. The monitor or visual display unit  19  will be positioned so as to be readily viewable by the driver of a vehicle. 
     Referring now to  FIG. 3 , a vehicle  20  is illustrated schematically from above, and the camera  1 , as described above, is shown mounted in position on a vehicle. The camera is mounted in a fixed position, with the optical axis  21  of the lens  5  aligned with the longitudinal axis of the vehicle  20 , so that the camera can capture an infra-red image of the road in front of the vehicle. 
     In the embodiment of  FIG. 3 , the sensor  4  provides a signal to the signal processor  2 , which indicates the speed of the vehicle, and the signal processor  2  processes the signal representative of the image so that the horizontal width of the field of view of the image displayed is decreased as the speed of the vehicle increases. 
     When the vehicle is stationary, or travelling at a very slow speed, the signal processor  2  processes the signal from the camera  1  so that the display unit  3  displays a very wide image of the roadway in front of the vehicle. This image may have an angular field of view of α  1 , as shown in  FIG. 3 . 
     For purposes of explanation,  FIG. 3  illustrates schematically four pedestrians standing in a roadway in front of the vehicle, identified as pedestrians A, B, C and D. With the relatively wide angular field of view α  1  of the displayed image when the vehicle is stationary or travelling slowly, all four pedestrians are shown in the image presented to the driver of the vehicle by the image display unit  3 , as shown in  FIG. 4 . 
     However, as the speed of the vehicle increases, the signal processor  2  reduces the angle of the field of view of the image that is presented on the display, whilst simultaneously magnifying the image so that the image still completely fills the display. Thus, as shown in  FIG. 5 , only the central pair of pedestrians B and C are illustrated when the vehicle is travelling swiftly, the pedestrians A and D no longer being present in the displayed image. 
     It is thus to be appreciated that when the vehicle is travelling slowly, for example in a built-up area, the image displayed will be wide enough to include any cycle tracks, walkways or the like, located at the side of the roadway that the vehicle is driving along, so that the driver of the vehicle may be alerted to potentially dangerous situations, such as pedestrians about to walk into the roadway. However, when the vehicle is travelling swiftly, a relatively narrow field of view is presented to the driver of the vehicle, showing the roadway in front of the vehicle. 
     In the embodiment described above, the signal processor  2  electronically processes the signal to select the field of view which is displayed on the display unit  3  or  19 . It is to be appreciated, however, that in a modified embodiment of the invention the field of view displayed on the display unit  3  or  19  may be adjusted by altering the focus of the lens  5  using the focusing ring, to provide an “optical zoom” effect, so that the optics of the camera are adjusted to ensure that the appropriate image is displayed. 
       FIG. 6  illustrates a further embodiment of the invention. In this embodiment of the invention a camera  1  of the type described above is mounted in a fixed position on a vehicle  20  with the optical axis  21  of the camera aligned with the longitudinal axis of the vehicle. 
     The camera is adapted to receive an optical image over a very wide angular field a  3 . Ordinarily the image displayed by the display device will be selected so that the image corresponds to a field of view having an angular width a  1 , with that image being centered on the optical axis  21  of the camera. Thus, where four notional pedestrians A, B, C and D are shown standing in front of the motor vehicle  20 , all four pedestrians will be within the image displayed by the display unit, if the vehicle is travelling straight. 
     However,  FIG. 6  illustrates the vehicle in a “cornering” situation. The steering wheels  22  provided at the front of the vehicle have been turned so that the rolling direction  23  of the wheel is off set by an angle α  4  relative to the initial rolling direction  24  of the wheels  22  when the steering wheels are aligned with the longitudinal axis of the vehicle for straight driving. The vehicle is thus cornering. 
     The sensor unit  4 , in this embodiment, senses the angle α  4  and controls the signal processor  2  so that the image which is displayed by the display unit is off set from the optical axis  21 , so as to display the environment into which the vehicle will move. Thus, the angle of field of view now displayed is shown as angle α  5 .  FIG. 7  illustrates the display, showing that the display only shows the two pedestrians C, D, provided at the end of the row of pedestrians, with the other two pedestrians A, B, not being displayed. 
     It is thus to be appreciated that, in the embodiment shown in  FIG. 6 , the field of view that is displayed is determined in accordance with the angular position of the rolling direction of the front steering wheels  22  of the vehicle. 
     In a similar way, the field of view that is displayed may be determined from the driving direction of the vehicle, for example as determined from a GPS sensor. 
     It is to be appreciated that various modifications may be effected to the arrangement described above. In one embodiment of the invention, the signal processor  2  operates so that when the vehicle corners at low speed, the width of the field of view presented on the display increases while the field of view remains aligned with the optical axis  21 , whereas when cornering at a higher speed, the overall angular width of the field of view is maintained, but the field of width is off-set from the optical axis  21 . The angle of off set from the optical axis  21  is preferably equal to the angle α  4 . 
     In the present Specification “comprise” means “includes or consists of” and “comprising” means “including or consisting of”.