GB695584A - Improvements in or relating to circuits for stabilizing cathode beams in alternativepositions - Google Patents

Abstract

695,584. Cathode-ray tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 9, 1951 [Feb. 14, 1950], No. 3193/51. Class 39(i) [Also in Groups XIX and XL(c)] The Figure shows a circuit in which a C.R. tube 1 comprises a cathode 2, control electrode 3, beam producing means 4, deflecting electrodes 5, 6 and collecting electrodes 7, 8, 12, 13. The electrode 7 has apertures 7<SP>1</SP> and collecting electrode 8 is connected to the deflection electrode 6 so that the electron beam may occupy any one of a number of stable positions. Negative pulses applied consecutively at point 16 cause the beam to move from a given stable position to the next one in a left-wise direction successively so that after six input pulses the beam will have been moved from its initial position to the extreme left-hand position in which it is incident on the left-hand edge of the left-hand end aperture 7<SP>1</SP> of collecting electrode 7. the secondary emissive electrode 12 and the adjacent further collecting electrode 13 are so biased that normally the potential of electrode 13 is greater than that of electrode 12. The seventh applied pulse at point 16 deflects the beam so that it strikes electrode 12 which emits secondary electrons which pass to electrode 13. Hence electrodes 12 and 13 become charged positively and negatively respectively, the negative pulse at electrode 13 being transmitted via capacitor 14 to deflecting electrode 6 so that the beam is deflected still further to the left. After a short time the potentials of electrodes 12 and 13 become substantially constant and capacitor C at point 16 tends to discharge thus the beam moves to the right until it leaves electrode 12 when electrode 13 rises rapidly in potential. This positive pulse is transmitted via capacitor 14 to electrode 6 to deflect the beam rapidly back to its initial right hand position, the negative pulse produced at electrode 12 is applied via capacitor 17 to the control electrode 3 to cut-off the beam during the fly-back period. The fly-back may be accelerated by connecting electrode 12 via a capacitor to the deflection electrode 5. In a modification the electrode 12 may be coupled to the beam producing means 4 instead of to control electrode 3.