Abstract: A process and device for automatic recognition of an object such as a road sign includes a laser beam source providing a laser beam capable of passing through a modulator on which an intensity spectrum of reference signs and a sign to be recognized has been pre-recorded. A converging lens positioned downstream of the modulator, as well as devices for observing and/or analyzing the spectrum occurring at the focal plane of the lens. These devices include apparatus for detecting peaks indicating that a reference sign is identical to a sign to be recognized, as well as apparatus to separate those peaks from spurious peaks. As an example, this device can automatically recognize speed limit signs on roads or freeways.