1.  Field of the Invention
The present invention relates to a traffic monitoring device for monitoring the number of objects such as, for example, passers-by then moving through a supervised sector defined at, for example, a doorway provided with a revolving door. 
2.  Description of Related Art
As a security technology for curbing the flow of information from a corporate building, it has become a recent wide spreading trend to install the authenticating device at an important doorway of the corporate building so that the door at the doorway can be opened only when the authenticating device identifies the bearer of an ID card or fingerprint by the ID card or fingerprint of the bearer. 
According to the conventional security technology of the kind referred to above, precaution is needed to avoid the unauthorized entry of someone other than the bearer of the ID card or fingerprint, who attempts to sneak through the doorway together with the bearer who has been authorized by the authenticating device at the doorway to pass through the doorway.  In view of this, the patent document 1 listed below, for example, suggests a traffic monitoring device for monitoring the number of passers-by then gathering in crowds by analyzing the area of an image to be analyzed, which area is a showing of passers-by appearing in a plurality of sliced images, in reference to the benchmark representing the position of the peak point in the three dimensional image data for each of selected closed regions. 
On the other hand, the patent document 2 listed below, for example, suggests, as a different monitoring means, a method of determining the number of objects based on the volume of those objects in reference to three dimensional object information representing the objects appearing in the supervised sector.