Method and means for reading electronic signal patterns stored on a

Abstract

A scanning system for optoelectronically recorded signal patterns stored in a plural layer medium consisting of inorganic materials throughout and featuring a dielectric storage layer at the surface which faces an electron beam source. The source beam first searches for a position mark associated with an image frame on the medium in order to establish a precise home position of the beam and associated coordinate axes prior to commencing the scan operation on that medium frame. Then the beam scans a raster on the medium spending a certain dwell time at each resolution element of the raster. Each time a frame is reached, the system is capable of altering the beam current in response to a pre-recorded exposure code in order to achieve the optimal retrieval of all information stored image-wise within said frame. The system then collects electrons emitted from the medium due to the scanning beam in a collector, which incorporates a highly sensitive amplifier, for further processing, with the medium being movable frame by frame as desired. In another system version, the electronic image on the medium as read using a sensing needle array that scans close to the medium surface making it possible to extract tunnelling electrons through the natural electron surface cloud as a result of an external electrical field applied between the needle and the medium. The 'tunnelling current' is modulated by internal, image-wise electrical field domains and the amplitude of the current is representative of the electronic image stored in the medium.