Patent Publication Number: US-2007115454-A1

Title: Environmental detection system with two spaced-apart emitters and receivers

Description:
BACKGROUND OF THE INVENTION  
      The invention relates to an environment detection system consisting of at least two emitters (S 1 , S 2 ) of electromagnetic waves and two receivers (E 1 , E 2 ) for receiving reflections of the emitted waves. The first emitter (S 1 ) and an immediately adjacent first receiver (E 1 ) are directed towards a first target area (Z 1 ) and, spaced apart therefrom, while a second emitter (S 2 ) and an adjacent second receiver (E 2 ) are directed towards a second target area (Z 2 ).  
      In future, such environment detection systems will be particularly employed in motor vehicles for longitudinal control, tracking error warning and tracking, or for taking measures in the event of an imminent crash.  
      The emitters generate, corresponding to a predetermined dispersion, one illuminated target area each, towards each of which one receiver is directed that detects the reflections from the target area, wherein the emitter and the receiver, as a rule, are arranged immediately adjacent to each other and the target area, dependent on the angle of dispersion, is approximately conical. For covering the complete road, the emitters must comprise an appropriate distance between each other. While the conical target areas meet at great distances from the vehicle if the emitters comprise an appropriate distance to each other, there is an area in the near range that cannot be covered. For covering this area, an additional, third emitter and an appropriately oriented receiver would have to be provided (see  FIG. 1 ).  
     SUMMARY OF THE INVENTION  
      The object of the invention is to provide an alternative environment detection system that enables covering to be as complete as possible. This object is achieved by an environment detection system consisting of at least two emitters of electromagnetic waves and two receivers for receiving reflections of the emitted waves. The first emitter and an immediately adjacent first receiver are directed towards a first target area and, spaced apart therefrom, a second emitter and an adjacent second receiver are directed towards a second target area.  
      The invention is based on the idea of directing, by employing appropriate optical means, at least a proportion of the waves emitted by an emitter towards the third target area to be covered and detecting reflections occurring in that area by means of the spaced-apart receiver, i.e. coupling the emitters and receivers crosswise in the end. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will now be explained in greater detail on the basis of exemplary embodiments and figures.  
      Brief Description of the Figures:  
       FIG. 1  Prior-art environment detection system in a motor vehicle;  
       FIG. 2  Realization of an inventive environment detection system in the first operating phase;  
       FIG. 3  Environment detection system in the second operating phase. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows an environment detection system in a motor vehicle that is known to be capable of being used for longitudinal control or pre-crash recognition or other applications in future. It comprises at least two emitters S 1 , S 2  of electromagnetic waves that are arranged on the right and left sides of the vehicle and emit in the direction of motion in this example. Correspondingly, two receivers E 1 , E 2  are provided that receive reflections of the emitted waves, wherein the first emitter S 1  and the first receiver E 1  are directed towards a first target area Z 1 , and a second emitter S 2  and a second receiver E 2  are directed towards a second target area Z 2 , thereby completely covering the front area in front of the vehicle at least from a certain distance onwards. An uncovered area remains in the near range on account of the conical widening of the target areas in the direction of motion.  
      Therefore the invention proposes that, as indicated in  FIG. 2 , at least the first emitter S 1  and preferably both emitters S 1  and S 2  comprise/s optical means that at least occasionally direct at least a proportion of the waves emitted by this emitter S 1  towards the third target area Z 3  and that at least the second receiver E 2  and preferably also the first receiver E 1  comprise/s optical means that at least occasionally direct reflections of the waves emitted by the first emitter S 1  towards the third target area Z 3  towards the second receiver E 2 . Such optical means can include appropriately adapted lenses, prisms or lenses of the headlight. These optical means can be occasionally arranged in front of the emitters and receivers for illuminating and covering the third target area Z 3  so that Z 1 , Z 2  and Z 3  are covered in turns.  
      Preferably however, the optical means are permanently arranged in front of the first emitter S 1  and the second receiver E 2  and direct in each case only a proportion of the emitted waves towards target area Z 3  and from this target area Z 3  on to receiver E 2 , respectively.  
      During a first operating phase, the first emitter S 1  emits, wherein at the same time the first receiver E 1  covers the first target area Z 1  and the second receiver E 2  covers the third target area Z 3  while the second emitter S 2  is inactive (see  FIG. 2 ).  
      During a second operating phase according to  FIG. 3 , the second emitter S 2  emits, wherein the second receiver E 2  covers the second target area Z 2 . Of course, the first receiver E 1  can cover the third target area Z 3  during the second operating phase if preferred. In this case, the third target area is covered twice as often as the first and second target areas but this is desired since the third target area comprises the area immediately in front of the vehicle and covering is particularly time-critical there.  
      The third target area Z 3  at least partially covers a near range situated between the first and second target areas Z 1 , Z 2  but can certainly overlap them.  
      Timing control of the emitters and receivers and the evaluation of the receiver signals and the assignment of the target areas are carried out in a central evaluation unit  1  that then supplies the processed signals to the corresponding application units.