Electron-image tube apparatus with improved acuteness of the image corners

Claim 1

ELECTRON IMAGE TUBE APPARTUS, COMPRISING AN ELECTRON IMAGE TUBE, SAID ELECTRON IMAGE TUBE INCLUDING AN ENVELOPE HAVING A PLANAR MEMBER, A FIRST PLANE ELECTRODE POSITIONED ON SAID PLANAR MEMBER IN SAIE ENVELOPE, A SECOND PLANE ELECTRODE IN SAID ENVELOPE, MEANS FOR PRODUCTING ELECTROSTATIC AND ELECTROMAGNETIC FIELDS IN SAID ENVELOPE, AND MEANS FOR TRANSFERRING ANE ELECTRON IMAGE HAVING A CENTRAL AREA AND PERIPHERAL CORNER AREAS FROM SAID FIRST PLANE ELECTRODE TO SAID SECOND PLANE ELECTRODE UNDER THE COMBINED EFFECT OF SAID ELECTROSTATIC AND ELECTROMAGNETIC FIELDS; AN ELONGATED MAIN MAGNETIC FOCUSING COIL SURROUNDING SAID ELECTRON IMAGE TUBE; AND AN AUXILIARY COIL POSITIONED IMMEDIATELY ADJACENT THE FIRST PLANE ELECTRODE OF SAID ELECTRON IMAGE TUBE, SAID AUXILIARY COIL BEING OF SUBSTANTIALLY ANNULAR CONFIGURATION AND HAVING AN INNER PERIPHERY, AN OUTER PERIPHERY AND A RADIAL WIDTH BETWEEN SAID INNER AND OUTER PERIPHERIES, THE INNER PERIPHERY OF SAID AUXILIARY COIL LYING ADJACENT THE CORNERS OF THE AREA OF SAID FIRST PLANE ELECTRODE OCCUPIED BY SAID IMAGE, THE OUTER PERIPHERY OF SAID AUXILIARY COIL BEING SPACED FROM SAID MAIN FOCUSING COIL BY A DISTANCE AT LEAST AS GREAT AS THE RADIAL WIDTH OF SAID AUXILIARY COIL, SAID AUXILIARY COIL BEING ADAPTED TO BE TRAVERSED BY A CURRENT FLOWING IN THE SAME DIRECTION AS A CURRENT FLOWING IN SAID MAIN FOCUSING COIL TO PROVIDE AN AUXILIARY ELECTROMAGNETIC FIELD INTERACTING WITH THE ELECTROMAGNETIC FIELD PRODUCED IN SAID ELECTRON IMAGE TUBE TO RESHAPE THE ELECTROMAGNETIC FIELD PRODUCED IN SAID ELECTRON IMAGE TUBE IN A DETERMINED MANNER IN THE CORNER AREAS OF SAID IMAGE TO SUBSTANTIALLY ELIMINATE FIELD CURVATURE AND TO SUBSTANTIALLY AVOID VARIATION OF THE ELECTROMAGNETIC FIELD PRODUCED IN SAID ELECTRON IMAGE TUBE IN THE CENTRAL AREA OF SAID IMAGE.