Method and apparatus for automatic optical recognition of road signs

DETAILED DESCRIPTION Consequently, an object of this invention is to overcome such problems by providing an automatic recognition process and device consisting of a detection system reacting very quickly to the signal corresponding to the received information, such that there is practically no delay--which could be dangerous for the vehicle--between the time the received information is captured and detected, even when the vehicle is traveling very fast.
To this end, an object of this invention is to provide a process for automatic recognition of an object, such as a road sign, which comprises the steps of: displaying on a screen an input image containing an image of the sign to be recognized as well as images of reference signs; passing a laser beam through that screen and an initial lens and then focusing the laser beam on a modulator or similar device capable of recording an intensity spectrum; lighting up the modulator with a laser beam; causing said laser beam leaving the modulator to pass through a second lens in order to produce another spectrum supplied to a detection system; and determining whether the sign to be recognized is identical to one of the reference signs based on said spectrum; wherein the determining step involves detecting correlation peaks within the focal plane of the second lens between the various signs contained in the input image, in such a way that the presence of intensity peaks exceeding a given threshold and offset with respect to the optical center of the image indicates that the sign to be recognized is identical to one of the reference signs.
Another feature of this process is that a landscape image containing the sign to be recognized undergoes a contour detection process in order to adapt the landscape image to the input screen and decrease the spectral range.
According to yet another feature of this process, with the input image containing only two reference signs, only a portion of the landscape image containing the sign to be recognized is captured so that the sign is located within the input image on a line running between the two references