GB455736A - Improvements in cathode ray tubes - Google Patents

Abstract

455,736. Cathode - ray tubes. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, Emmasingel, Eindhoven, Holland. Oct. 22, 1935, No. 29179. Convention date, Jan. 31. [Class 39 (i)] In a cathode-ray tube, the electrons at the entry of the region in which the beam may be laterally deflected are directed to a point P on the axis of the beam whose distance from the entry Q of the deflection region is between one quarter and one half of the length of the deflection region, and the current intensity and speed of the electrons, and consequently the dispersion, are given such a value that the electrons do not cross the axis of the beam and that the point R of the axis of the beam at which the beam has its smallest diameter is located beyond the " direction point" P and at least half-way along the deflection region, means being provided for focusing the electrons after leaving the deflection region. The arrangement relates to tubes such as oscillographs and oscillation generators and amplifiers in which a large dispersion is tolerated for the sake of increased sensitivity, and the limits prescribed prevent undue spreading of the beam in the deflection region. Preferably the ratio of RQ to PQ is made as large as possible, the theoretical maximum being 2. In the form shown in Fig. 1, the point P is one quarter and the " middle point" R is one half of the distance along the region bounded by the deflection plates 4, 5. The beam is symmetrical about the deflection region and the sensitivity is a maximum. The beam is produced by the cathode 1, control electrode 2 and anode 3, and after deflection the beam is focused by known means on the fluorescent screen or output electrode 10. The plates may be shaped to approach the beam more closely as shown by the dotted lines 11, 12. In Fig. 2, the beam is still symmetrical but the distance PQ is greater than one half RQ and the sensitivity is less than in Fig. 1. In a further modification, P is at the same point as in Fig. 2, but R is at the maximum distance. The beam is not symmetrical and the sensitivity is further reduced. The Specification as open to inspection under Sect. 91 comprises a modification, Fig. 4 (Cancelled), in which the direction point P is further than half-way along the deflection region and the middle point R is at the point of impact on the screen or plate 10. A further arrangement is described in which the middle point of the beam is beyond the point of impact and is thus virtual. In both cases the ratio of RQ to PQ has the maximum value 2. This subject-matter does not appear in the Specification as accepted.