Method of recording wide-band signals on a thermoplastic film by use of a beam of electrons

Claim 1

A method of recording a wide-band signal on a master record medium in the form of a groove which is to determine the shape of a corresponding groove in a derived record medium which groove therein is to be tracked by a reproducing stylus, comprising the steps of: directing a beam of electrons at a thin film of electrically resistive thermoplastic material which is supported by a conductive substrate; moving said film relative to said beam so as to cause said beam to deposite a continuous track of electrical charge on the film; modulating the intensity of the beam in accordance with the said wide-band signal; focussing said beam to produce a focus having an effective diameter, in a sense along the direction of progression of the track, which is substantially less than the shortest wave-length in said wide-band signal; producing astigmatism in said beam to produce an elliptical focus which is elongate in a direction transverse the direction of progression of said track and has in the said transverse direction a second diameter which is a substantial fraction of the width of the track, so as thereby to cause said track to be of a width which is significantly wider than the effective diameter and has a charge density which is substantially greater in the middle of the track than at the edges thereof; and heating and cooling said film.

Claim 2

A method of recording a wide-band signal on a master record medium in the form of a groove which is to determine the shape of a corresponding groove in a derived record medium which groove therein is to be tracked by a reproducing stylus, comprising the steps of: directing a beam of electrons at a thin film of electrically resistive thermoplastic material which is supported by a conductive substrate; moving said film relative to said beam so as to cause said beam to deposite a continuous track of electrical charge on the film; modulating the intensity of the beam in accordance with the said wide-band signal; focussing said beam to produce a focus having an effective diameter, in a sense along the direction of progression of the track, which is substantially less than the shortest wave-length in said wide-band signal; producing astigmatism in said beam to produce an elliptical focus which is elongate in a direction transverse the direction of progression of said track and has in the said transverse direction a second diameter which is a substantial fraction of the width of the track, so as thereby to cause said track to be of a width which is significantly wider than the effective diameter and has a charge density which is substantially greater in the middle of the track than at the edges thereof; and heating and cooling said film.

Claim 5

A method of recording a wide-band signal on a master record medium in the form of a groove which is to determine the shape of a corresponding groove in a derived record medium which groove therein is to be tracked by a reproducing stylus, comprising the steps of: aiming an electron column so as to direct a beam of electrons at a thin film of electrically resistive thermoplastic material which is supported by a conductive substrate; rotating said film in its plane and simultaneously translating said film so as thereby to cause said beam to deposit a continuous spiral track of electric charge on the film; generating a control signal for modulating the intensity of the beam in accordance with the said wide-band signal; focussing said beam to produce a focus having an effective diameter in a sense along the direction of progression of the track, which is substantially less than the shortest wavelength in said wide-band signal; producing astigmatism in said beam to produce an elliptical focus which is elongate in a direction transverse the direction of progression of said track and has in the said transverse direction an effective diameter which is a substantial fraction of the width of the track; coupling said control signal to said electron column through a high voltage coupling, so as to modulate the intensity of said beam in accordance with the said wide-band signal; and heating and cooling said film.

Claim 6

A method of recording a wide-band signal on a master record medium in the form of a groove which is to determine the shape of a corresponding groove in a derived record medium which groove therein is to be tracked by a reproducing stylus, comprising the steps of: aiming an electron column so as to direct a beam of electrons at a thin film of electrically resistive thermoplastic material which is supported by a conductive substrate; rotating said film in its plane and simultaneously translating said film so as thereby to cause said beam to deposit a continuous spiral track of electric charge on the film; generating a control signal for modulating the intensity of the beam in accordance with the said wide-band signal; focussing said beam to produce a focus having an effective diameter in a sense along the direction of progression of the track, which is substantially less than the shortest wavelength in said wide-band signal; producing astigmatism in said beam to produce an elliptical focus which is elongate in a direction transverse the direction of progression of said track and has in the said transverse direction an effective diameter which is a substantial fraction of the width of the track; coupling said control signal to said electron column through a high voltage coupling, so as to modulate the intensity of said beam in accordance with the said wide-band signal; and heating and cooling said film.