GB756551A - Improvements in or relating to electron-image apparatus - Google Patents

Abstract

756,551. Cathode-ray tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. March 6, 1953 [March 10, 1952], No. 6287/53. Class 39 (1). The magnetic electron lens of an image converter tube consists of three windings so designed that the overall magnification may be varied by a single control while maintaining a sharp image. With an arrangement of given geometry the number of ampere-turns i, n necessary for each value of magnification V, is determined, Fig. 1, preferably for the same rotation of the image. The number of turns for each winding n1, n2, n3 is then chosen so that within a certain range the sum of the currents through the windings is constant. In the series arrangement of coils 9, 12, 15, Fig. 3, the settings of ganged rheostats 11, 14 are so chosen that at every setting the sum of the currents through the windings 12, 15 is equal to the difference between the constant current i and the current in the winding 9. One rheostat may be a linear resistor and the other graded in the required manner. It may be composed of a series of linear resistances of graded magnitude. The two stabilizing tubes 3, 4 and the resistance 5 keep the voltage between terminals 6 and 7 constant. In another arrangement, Fig. 4, with the windings 9, 12, 15 in parallel, the currents in the windings 12, 15 are controlled by triodes 22, 23. The control voltages are derived from ganged potentiometers 24, 25 in series with the three parallel impedance arms. One of the potentiometers is linear while the other has a graded resistance which is such that the sum of the currents in the windings is constant. The overall current is kept constant by the current regulator 20. Winding 9 surrounds the photo-cathode, second winding 12 chiefly controls the magnification and third winding 15 serves mainly for correcting the image rotation. Specification 506,825, [Group XL], is referred to.