GB1418033A - Correcting colour television display errors - Google Patents

Abstract

1418033 Cathode-ray tube circuits PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 14 Nov 1972 [17 Nov 1971] 52507/72 Addition to 1230162 Heading H4T In colour television display apparatus a transductor 1 (Fig. 1) the windings 2<SP>1</SP>, 211 of which are supplied with opposite polarity line fly-back pulses acts as a modulator to provide a correction current i K <SP>1</SP>, i K <SP>11</SP>, comprising a line frequency current amplitude modulated at field frequency (Fig. 3C), which flows in opposite directions in the two halves 6<SP>1</SP>, 6<SP>11</SP> of the field deflection coils which are supplied with deflection energy from field deflection generator 7. This provides, in known manner, a quadripolar field which corrects for astigmatic deflection errors and in accordance with the characterizing feature of the present invention a known kind NORTH-SOUTH raster correction circuit comprising capacitors 10, 11 and inductance 12 utilizes the voltage across the windings 3<SP>1</SP>, 3<SP>11</SP> to provide a correction current i N (Fig. 3b) which flows in the same direction in both deflection coil halves 6<SP>1</SP>, 6<SP>11</SP>. Fig. 4 shows a modification in which the current i K <SP>1</SP>, i K <SP>11</SP> producing quadripolar field is generated in the line deflection coils 19<SP>1</SP>, 19<SP>11</SP>, Fig. 5 shows a modification of Fig. 4 in which the windings 3<SP>1</SP>, 3<SP>11</SP> and 4<SP>1</SP>, 4<SP>11</SP> are formed a single tapped winding and Fig. 6 shows a modification in which the deflection coils 19<SP>1</SP>, 19<SP>11</SP> are fed in parallel instead of in series. In the embodiment of Fig. 1, the addition of coupled inductor 12<SP>1</SP>, capacitor 17 and resistor 18 allows correction to be effected for residual corner errors which may occur even when the deflection coils are substantially without anisotropic astignation. The convergence winding for dynamic blue lateral convergence, the errors in which are larger than for red and green in tubes having large deflection angles, may be connected between a source of line fly-back pulses and a tap on the inductor 5 (Figs. 7 and 8, not shown). A typical "E"-shaped core which may be employed for the transductor 1 is described with reference to Fig. 9 (not shown).