Optical scanning unit for mark sensing

Claim 1

Optical-scanning apparatus comprising laser means for producing a beam of monochromatic light, means for lineally deflecting said beam through a predetermined distance transversely across the surface of a record to be scanned, means to displace said record in a direction perpendicular to the path of travel of said beam, a light confining hood assembly extending over the path of travel of said beam and containing means selectively responsive only to light intensity variations induced by the passage of said beam over intelligence representing indicia located on said record surface for providing first discrete electrical signals representative thereof, clocking grid means disposed adjacent said record surface including a masking element defining a multiplicity of discrete apertures separated by light impervious wall members for incrementally subdividing said predetermined distance into a predetermined number of discrete segments prepatterned in accord with the intelligence being scanned, beam splitting means disposed adjacent to said record surface and extending over the path of travel of said lineally deflected beam for directing a portion of said beam through the masking element of said clocking grid during the lineal deflection thereof through said predetermined distance, and means responsive to the light intensity variations induced by the sequential blockage and passage of said portion of said beam through said masking element during its traverse thereof for providing a sequence of second discrete electrical signals selectively representative of the location of said beam at all times during the traverse of said record whereby correlation of said first electrical signals with the complemental signals in said sequence of second discrete signals defines the location and nature of said intelligence representing indicia on said record.