GB827222A - Improvements in or relating to electron beam deflecting systems - Google Patents

Abstract

827,222. Electron beam deflecting apparatus. GENERAL ELECTRIC CO. Ltd. Oct. 10, 1957 [Dec. 17, 1956], No. 38441/56. Class 39(1). An electron beam deflecting system of increased sensitivity includes primary deflecting means and secondary deflecting means which consisting of two pairs of plates which produce a further deflection of the beam, perpendicular to and proportional to the primary deflection. In one embodiment the plates 1, 2, Fig. 1, form the primary means, and plates 3, 4, 5, 6 form the secondary means. These plates are approximately triangular in shape and are placed so that the distance the beam travels between them is proportional to its primary deflection. Plates 3, 5 are connected together and maintained at a positive potential whilst 4, 6 are maintained at a negative potential, both with respect to the final anode of the electron accelerating system. The line PO indicates the position of the undeflected beam, whilst OX represents a deflection produced by a potential difference between plates 1, 2, and OY represents the resultant deflection produced by the entire system. When the beam is to be deflected in two mutually perpendicular directions it is preferable to apply the system to produce that deflection which occurs most frequently, for example the line scan in a television receiver. In a modification the secondary means comprises plates 7, 8, 9, 10, Fig. 2, of equal length and curved to present their convex surfaces to the beam. Plates 7, 9 are connected to a positive voltage source and plates 8, 10 are connected to a negative voltage source, both with respect to the final anode of the electron accelerating systems. The field between the plates increases with the distance from the centre of the system, thus the deflection produced by the secondary deflection system is again perpendicular to and proportional to the primary deflection. A further increase in sensitivity may be obtained by curving the secondary deflection plates to follow the path of the electron beam, thus reducing the necessary spacing between the plates. The primary deflecting means may be either magnetic or electrostatic.