| 摘要 |
<p>840,079. Electron lenses. PHILIPS ELECTRICAL INDUSTRIES Ltd. Dec. 9, 1958 [Dec. 11, 1957], No. 39670/58. Class 39(1). In a 3-colour television picture tube comprising three guns arranged at the corners of a triangle, astigmatism and coma are reduced by making the meridional image plane for the direction of deflection which is parallel to the plane containing two of the guns, and the sagittal image plane for the other direction of deflection, both coincident with the screen. The tube referred to is of the mask type. The coils of the Y and X deflection systems are pairs of asymmetrical half coils, as shown in Figs. 2 and 4, producing the variation of the magnetic field HI2 and HII2 in the Z direction shown in Figs. 3 and 5 respectively. The theory for the correction of the errors and the design of the coils is given in the Specification. In Fig. 6, the deflection system consists of two ferromagnetic cores 11, 12 each with eight toroidal coils. The X deflection system consists of four coils on core 11 (only two, 13 and 14 shown), and four coils on core 12 (only two, 17 and 18 shown), coil 21 and 22 are two of the four Y deflection coils on core 11 and coils 25 and 26 are two of the four Y deflections coils on core 12. The angles subtended by the coil pairs are 25 degrees and 43 degrees for the X coils and 33 degrees and 20 degrees for the Y coils. The eight coils in each set may be connected as shown in Fig. 9 or Fig. 10, the circuit including a variable inductance 30, Fig. 9, or 34, Fig. 10. Dynamic convergency is exerted on the beam produced by the gun outside the plane containing the other two guns to ensure that this beam is superimposed on the other two beams throughout the deflection. For this purpose currents proportional to the squares of the currents for producing the X and Y deflections are passed through an additional set of deflections. Where the X and Y deflection currents are sawtooth, these additional currents may be parabolic currents of line and raster frequencies. Dynamic convergency may also be applied to the beams from the two guns in the same plane for complete correction of the deflection errors.</p> |
