Abstract:
A device for counting and determining the direction of passage of living beings. A first cell delivers an electrical signal representing the passage of a living being. A second pryoelectric cell delivers a second electrical signal. A processing unit analyzes the signals and determines the number of living beings moving past and their direction of movement.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is based on and claims priority to International Application PCT/EP2007/002558 filed on Mar. 22, 2007 and French Patent Application No. 06/02665 filed on Mar. 27, 2006, the contents of which are hereby incorporated by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a device for counting and determining the direction of passage of living beings. It finds its application in the field of counting and determining the direction of passage of persons on paths or in buildings. However, it can also apply to the counting and determination of the direction of passage of animals on paths. 
       FIG. 1  depicts a device for determining the direction of passage  100  of a living being  114  of the prior art, which comprises a pyroelectric cell  102  and a processing unit (not shown). 
     The pyroelectric cell  102  is of the type comprising a first detection window  104  and a second detection window  106  disposed, horizontally, alongside each other. The pyroelectric cell  102  and in particular the first detection window  104  and the second detection window  106  are sensitive to infrared radiation, and the pyroelectric cell  102  delivers an electrical signal  200  representing the passage of the living being  114  in front of the detection windows  104  and  106 . The electrical signal  200  is shown in  FIG. 2   a.    
     The processing unit is connected to the pyroelectric cell  102  and receives the electrical signal  200  thus delivered and, from the analysis of this electrical signal  200 , it determines the direction of passage of the living being  114  in front of the device for determining the direction of passage  100 . 
     The parallelepipeds  110  and  112  of  FIG. 1  represent the zones of influence of the detection windows  104  and  106 . That is to say infrared radiation emitted inside the first zone of influence  110  is perceived by the first detection window  104  and infrared radiation emitted inside the second zone of influence  112  is perceived by the second detection window  106 . 
     The arrow  116  represents the direction of passage of the living being  114 . 
     The electrical signal  200  represents the electrical signal delivered by the pyroelectric cell  102  during the passage of the living being  114  in front of the pyroelectric cell  102 . The arrow  210   a  represents the direction of passage of the living being  114 . In the example in  FIG. 2   a , the arrow  210   a  repeats the direction of the arrow  116  in  FIG. 1 . 
     The maximum  202  represents the detection by the first detection window  104  of the passage of the living being  114  and the minimum  204  represents the detection by the second detection window  106  of the passage of the living being  114 . The secondary minimum  206  and the secondary maximum  208  represent the damping of the signal and depend on the elements making up the pyroelectric cell  102  and the processing unit. 
     If the living being  114  moves in a direction opposite to that of the arrow  116 , the electrical signal  200  is reversed, that is to say the signal passes first of all through the minimum  204  representing the passage of the living being  114  in front of the second detection window  106  and then a maximum  202  representing the passage of the living being  114  in front of the first detection window  104 . Such an electrical signal is depicted at  FIG. 2   b . The direction of passage of the living being  114  is then represented by the arrow  210   b.    
     The determination of the direction of passage of the living being  114  in front of the device for determining the direction of passage  100  therefore seems to be able to take place by analysis of the electrical signal  200 . 
     The problem with the device  100  of the prior art is that in fact, this determination is accurate only if the temperature of the living being  114  is greater than that of the device for determining the direction of passage  100 . 
     This is because, if the temperature of the living being  114  is lower than that of the device for determining the direction of passage  100 , the curves in  FIGS. 2   a  and  2   b  are reversed and there is then a lack of determination of the direction of passage of the living being  114 . 
     Thus, because of the reversal of the difference in temperature between the living being  114  and the device for determining the direction of passage  100 , there arises uncertainty with regard to the direction of passage of the living being  114  in front of the device for determining the direction of passage  100 . Such a reversal in the difference in temperature may exist when the device for determining the direction of passage  100  is placed in a heated corridor and the living being  114  comes from a place where the temperature is lower, for example outside, and his garments are cold. 
     In addition, such a device for determining the direction of passage  100  does not make it possible to count the number of living beings  114  passing in front of it. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is therefore to propose a device for counting and determining the direction of passage of living beings that does not have the drawbacks of the prior art, allowing counting of living beings as well as an exact determination of the direction of passage of the living beings. 
     To this end, there is proposed a device for counting and determining the direction of passage of living beings comprising:
         a first pyroelectric cell adapted to deliver an electrical signal of a first type representing the infrared radiation emitted by a living being passing in front of said first cell;   a second pyroelectric cell of the type comprising a first detection window and a second detection window and adapted to deliver an electrical signal of a second type representing the direction of passage of the living being in front of said second pyroelectric cell the first cell and the second pyroelectric cell being one above the other; and   a processing unit adapted to determine firstly the number of living beings passing in front of said device, by analysing the electrical signal of the first type, and secondly the direction of passage of the living beings passing in front of said device by analysing the electrical signal of the first type and the electrical signal of the second type.       

     According to a particular embodiment, the first cell is a pyroelectric sensor of the type comprising a first detection window and a second obscured detection window. 
     According to a particular embodiment, the determination of the direction of passage of the living beings passing in front of said device consist of analysing the level of the electrical signal of the second type at the moment when the living being leaves the cone of influence of the first detection window of the first cell. 
     Advantageously, the device for counting and determining the direction of passage comprises a cylindrical Fresnel lens disposed in front of each cell. 
     Advantageously, for each cell, the position of the focus of the Fresnel lens is such that the infrared radiation emitted by each living being is focussed substantially between the two detection windows of the cell in question. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The characteristics of the invention mentioned above, as well as others, will emerge more clearly from a reading of the following description of an example embodiment, the said description being given in relation to the accompanying drawings, among which: 
         FIG. 1  depicts a device for determining the direction of passage of a living being of the prior art; 
         FIG. 2   a  and  FIG. 2   b  depict curves representing the signal output from the pyrotechnic cell of the prior art; 
         FIG. 3  depicts a device for counting and determining the direction of passage of a living being according to the invention; 
         FIG. 4   a ,  FIG. 4   b ,  FIG. 4   c  and  FIG. 4   d  are the various curves representing the signal output from the second pyroelectric cell of the device for counting and determining the direction of passage of a living being according to the invention; 
         FIG. 5   a  and  FIG. 5   b  depict the curves representing the signal output from the first cell of the device for counting and determining the direction of passage of a living being according to the invention; and 
         FIGS. 6   a ,  6   b ,  6   c  and  6   d  depict the combination of curves representing the signal output from the second pyroelectric cell and the curves representing the signal output from the first cell of the device for counting and determining the direction of passage of a living being according to a particular embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  depicts a device for counting and determining the direction of passage  500  of a living being  114  according to the invention. The elements identical to the device for determining the direction of passage  100  of the prior art bear the same references. 
     Thus the device for counting and determining the direction of passage  500  according to the invention comprises:
         a first cell  502  adapted to deliver an electrical signal of a first type representing the passage of a living being  114  in front of the first cell  502 ;   a second pyroelectric cell  102  of the type comprising a first detection window  104  and a second detection window  106  and adapted to deliver an electrical signal of a second type representing the direction of passage of the living being  114  in front of the second pyroelectric cell  102 ; and   a processing unit adapted to determine firstly the number of living beings passing in front of the device  500  by analysing the electrical signal of the first type and secondly the direction of passage of the living beings  114  passing in front of the device  500  by analysing the electrical signal of the first type and the electrical signal of the second type.       

     According to a particular embodiment of the invention depicted in  FIG. 3 , the first cell  502  is a pyroelectric sensor  502  of the type comprising a first detection window  504  and a second obscured detection window. 
     In  FIG. 3 , the first cell  502  and second cell  102  are disposed close to each other and one above the other. 
     The detection windows  104 ,  106  and  504  are oriented vertically and the detection windows  104  and  106  of the second cell  102  are disposed, horizontally, one alongside the other. 
     So that the vision angle of each cell  102 ,  502  is not too extensive and therefore that each cell  102 ,  502  is solely influenced by a single living being  114  passing in front of the device  500 , the latter comprises, for each cell  102 ,  502 , a cylindrical Fresnel lens  508  disposed in front of each cell  102 ,  502 . Advantageously, for each cell  102 ,  502 , the position of the focus of the Fresnel lens  508  is such that the infrared radiation emitted by the living being  114  is focussed substantially between the two detection windows  104 ,  106 ,  504  of the cell  102 ,  502  in question. 
     The cone  506  represents the cone of influence of the first cell  502  and in particular of the first detection window  504  of the first cell  502 , that is to say any living being  114  entering this cone  506  is seen by the first cell  502 . 
     The cone  510  represents the cone of influence of the second cell  102 , that is to say any living being  114  entering this cone  510  is seen by the second cell  102  and in particular by the first detection window  104  and the second detection window  106 . 
     To allow better detection of each living being  114  passing the device  500 , and to avoid the passage of a plurality of living beings  114  being analysed as the passage of single living being  114 , the angle of each cone of influence  506 ,  510  is reduced to the maximum possible extent. 
     In addition, the fact that the first cell  502  and the second cell  102  are disposed one above the other makes it possible to align the cone  506  and the cone  510  vertically. Thus a single living being  114  influences simultaneously the first cell  502  and the second cell  102  and, when the living being  114  leaves one of the cones  506  or  510 , it also leaves the other cone  510  or  506 . Thus, when the living being  114  no longer influences one of the cells  502  or  102 , it no longer influences the other cell  102  or  502  respectively, which avoids faulty counting or faulty determination of the direction of passage. 
     This particular arrangement also makes it possible to obtain a compact device for counting and determining the direction of passage  500 . 
       FIG. 5   a  and  FIG. 5   b  depict the curves representing the signal output from the first cell  502  of the device for counting and determining the direction of passage  500 , that is to say the electrical signal of the first type. 
       FIG. 5   a  depicts the curve  602  when the external surfaces of the living being  114  are at a temperature lower than that of the device  500 . The curve  602  has a maximum that corresponds to the passage of the living being  114  in the cone of influence  506 , then an abrupt variation (here a drop) corresponding to the fact that the living being  114  leaves the cone of influence  506 , and then a return to the initial level. 
       FIG. 5   b  depicts the curve  604  when the external surfaces of the living being  114  are at a temperature greater than that of the device  500 . The curve  604  has minimum that corresponds to the passage of the living being  114  in the cone of influence  506 , and an abrupt variation (here a rise) corresponding to the fact that the living being  114  leaves the cone of influence  506 , and then a return to the initial level. 
     The processing unit can thus, by analysing the signal received from the first cell  502 , count the number of living beings  114  passing in front of the device  500  by incrementing a counter. In fact, in order to count a living being  114 , the processing unit analyses the electrical signal of the first type and increments the counter when it detects a first variation (rise  602  or fall  604 ) from the initial level, and then a second variation in a direction opposite to the first variation (fall or rise). 
     From the analysis of the signal received from the first cell  502 , the processing unit can thus determine whether the temperature of the living being  114  is less than or greater than that of the device  500 . The first cell  502  therefore fulfils a role of counting and temperature sensing cell that delivers an electrical signal representing the difference in temperatures between the device  500  and the living being  114 . 
       FIGS. 4   a ,  4   b ,  4   c  and  4   d  are the curves  310   a ,  310   b ,  410   a  and  410   b  representing the signal output from the second pyroelectric cell  102  of the device for counting and determining the direction of passage of a living being  500 , that is to say the electrical signal of the second type. These curves  310   a ,  310   b ,  410   a  and  410   b  have a less sharp profile than the curves  602  and  604  because they result from a combination of the electrical signals coming from the first detection window  104  and the second detection window  106  of the second cell  102 . In particular, the zone of return to the initial value of each of these curves  310   a ,  310   b ,  410   a  and  410   b  is disturbed. 
     The curve  310   a  represents the passage of a living being  114  whose temperature is less than that of the device  500  in a first direction represented by the arrow  300   a.    
     The curve  310   b  represent the passage of a living being  114  whose temperature is less that that of the device  500  in a second direction represented by the arrow  300   b.    
     The curve  410   a  represents the passage of a living being  114  whose temperature is greater than that of the device  500  in the first direction represented by the arrow  400   a , which is identical to the direction of the arrow  300   a.    
     The curve  410   b  represents the passage of a living being  114  whose temperature is greater than that of the device  500  in the second direction represented by the arrow  400   b , which is identical to the direction of the arrow  300   b.    
     The analysis, by the processing unit, of the signal of the first type and of the signal of the second type thus makes it possible to determine the direction of passage of the living being  114  in front of the device  500 . 
     The curve  310   a  has a maximum  302  that corresponds to the passage of the living being  114  in front of the first detection window  104  and then an abrupt drop and a minimum  304  that corresponds to the passage of the living being  114  in front of the second detection window  106 , then an abrupt rise that corresponds to the fact that the living being  114  emerges from the cone of influence  510 , and then a return to the initial level. 
     The curve  310   b  has an arrangement reversed with respect to the curve  310   a , that is to say it has the minimum  304  that corresponds to the passage of the living being  114  in front of the second detection window  106 , then an abrupt rise and the maximum  302  that corresponds to the passage of the living being  114  in front of the first detection window  104 , then an abrupt drop that corresponds to the fact that the living being  114  leaves the cone of influence  510 , and then a return to the initial level. 
     The curve  410   a  has a minimum  402  that corresponds to the passage of the living being  114  in front of the first detection window  104 , then an abrupt rise and a maximum  404  that corresponds to the passage of the living being  114  in front of the second detection window  106 , then an abrupt drop that corresponds to the fact that the living being  114  emerges from the cone of influence  510 , and then a return to the initial level. 
     The curve  410   b  has an arrangement reversed with respect to the curve  410   a , that is to say it has the maximum  404  that corresponds to the passage of the living being  114  in front of the second detection window  106 , then an abrupt fall and the minimum  402  that corresponds to the passage of the living being  114  in front of the first detection window  104 , then an abrupt rise that corresponds to the fact that the living being  114  leaves the cone of influence  510 , and then a return to the initial level. 
     As described above, apart from the electrical signal of the second type delivered by the second pyroelectric cell  102  and representing the direction of passage of the living being  114  in front of the detection windows  104  and  106 , the processing unit receives the electrical signal of the first type delivered by the first cell  502  and representing the passage of the living being  114  in front of the detection window  504 . Thus the processing unit receives both one of the electrical signals of the first type, depicted in  FIG. 5   a  or  5   b , and one of the electrical signals of the second type, depicted in  FIGS. 4   a ,  4   b ,  4   c  or  4   d.    
     After analysis of the electrical signal of the first type ( FIG. 5   a ,  FIG. 5   b ), received from the first cell  502 , the processing unit determines whether the temperature of the living being  114  is greater than or less than that of the device for counting and determining the direction of passage  500 . 
     Analysis of the electrical signal of the second type then makes it possible to determine the direction of passage of the living being  114 . In fact the determination of the temperature of the living being  114  compared with that of the device for counting and determining the direction of passage  500  limits the analysis to two of the four curves depicted in  FIGS. 4   a ,  4   b ,  4   c  and  4   d.    
     If the temperature of the living being  114  is less than that of the device for counting and determining the direction of passage  500 , the direction of passage of the living being  114  is given by the arrow  300   a  in  FIG. 4   a , or by the arrow  300   b  in  FIG. 4   b . If the signal of the second type is similar to the curve in  FIG. 4   a , that is to say the curve passes first of all through the maximum  302  and then through the minimum  304 , then the direction of passage is given by the arrow  300   a . If the signal of the second type is similar to the curve in  FIG. 4   b , that is to say the curve passes first of all through the minimum  304  then through the maximum  302 , then the direction of passage is given by the arrow  300   b.    
     If the temperature of the living being  114  is greater than that of the device for counting and determining the direction of passage  500 , the direction of passage of the living being  114  is given by the arrow  400  of  FIG. 4   c , or by the arrow  400   b  in  FIG. 4   d . If the signal of the second type is similar to the curve in  FIG. 4   c , that is to say the curve passes first of all through the minimum  402  and then through the maximum  404 , then the direction of passage is given by the arrow  400   a . If the signal of the second type is similar to the curve in  FIG. 4   d , that is to say the curve passes first of all through the maximum  404  and then through the minimum  402 , then the direction of passage is given by the arrow  400   b.    
     The various combinations between the signal of the second type output from the second pyroelectric cell  102  and the signal of the first type output from the first cell  502  of the device for counting and determining the direction of passage of a living being  500 , are represented by the curves in  FIGS. 6   a ,  6   b ,  6   c  and  6   d.    
     Thus knowledge of the temperature of the living being  114 , compared with that of the device for counting and determining the direction of passage  500 , makes it possible to determine precisely the direction of passage of the living being  114 . 
     As described above, the processing unit is adapted to count the number of living beings  114  who have passed in front of the device  500 . According to a particular embodiment, the processing unit counts, in a first register, the number of living beings  114  who have passed in the direction of the arrows  300   a  and  400   a  and, in a second register, the number of living beings  114  who have passed in the direction of the arrows  300   b  and  400   b.    
     For  FIGS. 6   a ,  6   b ,  6   c  and  6   d , the first cell  502  and the second cell  102  are disposed one above the other, and the first detection window  504  of the first cell  502  is disposed substantially on the same vertical axis as the first detection window  104  of the second cell  102 . 
       FIG. 6   a  depicts the passage of a living being  114  whose external temperature is less than that of the device for counting and determining the direction of passage  500 , and which passes in front of the said device  500  in the direction represented by the arrow  300   a.    
     The living being  114  thus first of all passes in front of the first detection window  504 ,  104  of each cell  502 ,  102  generating a first maximum  702  on the curve  602  and the second maximum  302  on the curve  310   a . During the forward movement of the living being  114 , the influence of it is felt at the second detection window  106  of the second cell  102 , represented here by the drop between the maximum  302  and the minimum  304 . The minimum  304  then represents the moment when the living being  114  influences mainly the second detection window  106  of the second cell  102 . During this passage from the maximum  302  to the minimum  304 , the living being  114  leaves the cone of influence  506  of the first detection window  504 , which generates a rapid variation (here a drop) in the signal delivered by the first cell  502 . At the end of the rapid variation, the curve  310   a , representing the signal of the second type, is at the minimum  304 , that is to say the living being  114  is situated in front of the second detection window  106  of the second cell  102 . Thus the determination of the direction of passage of the living being  114  passing in front of the device  500  can be determined by analysing the level of the electrical signal of the second type, at the moment when the living being  114  leaves the cone of influence  506  of the first detection window  504  of the first cell  502 . 
       FIG. 6   b  represents the passage of a living being  114  whose external temperature is less than that of the device for counting and determining the direction of passage  500  and that passes in front of the said device  500  in the direction represented by the arrow  300   b.    
       FIG. 6   c  represents the passage of a living being  114  whose external temperature is greater than that of the device for counting and determining the direction of passage  500  and passes in front of the said device  500  in the direction represented by the arrow  400   a.    
       FIG. 6   d  represents the passage of a living being  114  whose external temperature is greater than that of the device for counting and determining the direction of passage  500  and who passes in front of the said device  500  in the direction represented by the arrow  400   b.    
       FIGS. 6   b ,  6   c  and  6   d  are equivalent to  FIG. 6   a , and each shows the variations in the electrical signal of the second type which are coordinated with those of the electrical signal of the first type. In particular, when the living being  114  leaves the cone of influence  506  of the first detection window  504 , this generates a rapid variation (a drop or rise) in the signal delivered by the first cell  502  and, at the end of this rapid variation, the curve representing the electrical signal of the second type  310   b ,  310   c  and  310   d  is at the minimum  402  or maximum  302 ,  404 , that is to say the living being  114  is situated in front of the second detection window  106  of the second cell  102  or in front of the first detection window  104  of the second cell  102 . 
     Thus, in general terms, the determination of the direction of passage of the living being  114  passing in front of the device  500  consists of analysing the level of the electrical signal of the second type at the moment when the living being  114  leaves the cone of influence  506  of the first detection window  504  of the first cell  502 . In other words, when the thermal mass represented by the living being  114  leaves the cone of influence  506  of the first detection window  504  of the first cell  502 , the signal of the first type and also its representative curve  602  or  604  have a rising or falling edge that is sharp and very short in time. This instant then represents a remarkable event. Analysis of the signal of the second type of this instant makes it possible to determine the direction of passage of the living being  114 . 
     Naturally the present invention is not limited to the example and embodiment described and depicted but is capable of many variants accessible to persons skilled in the art. 
     For example, the various curves may be different according to the characteristics of the cells used and the characteristics of the electronic components constituting the processing unit. In particular the directions of variation may be reversed. 
     The curves may also be different if the first detection window of the first cell is aligned vertically with the second detection window of the second cell. However, there always exists a correspondence between the moment when the living being  114  no longer influences the first detection window of the first cell and the level of the electrical signal of the second type. 
     Although the invention is more particularly described in the case where the first detection window  504  of the first cell  502  is vertical, the invention can also function in the case where this detection window  504  is oriented horizontally.