Patent ID: 7214930

Claim:
A pulse generator comprising: a first plate having regions of optical characteristics that vary with a first periodicity (P 1 ); a second plate having regions of optical characteristics that vary with a second periodicity (P 2 ) juxtaposed with said first plate so that at least in a superimposition zone of the regions with said first and second periodicity, a region is formed with optical characteristics that vary with a third periodicity (P 3 ) that is a function of said first and second periodicities, said third periodicity being a Moiré pattern that is varied by a manual relative shifting of said first and second plates, the optical characteristics being selected from optical density, reflectivity, and transmissivity; and an optical sensor positioned to detect the periodically different optical characteristics of said third periodicity and to generate an electric signal corresponding to the detected periodically different optical characteristics of said third periodicity.