US2224587A - Method of operating cathode ray tubes - Google Patents

Description

DCC. 10, 1940. H BHRlNG I 2,224,587

METHOD OF OPERATING CATHODE RAY TUBES Filed July 16, 1937 Paetec D... 1o, 194g. g l 2,224,587"

" UNIT-'ED STTES OFFICE r Herlrlrtr zhring, Berlin-Zehlendorf, Germany;

assigner to the firm of Fernseh Aktien-Gesellschaft, Zehlendorf, near Berlin, Germany Application July 16, 1937, serial No. 154,093 In Germany July 13, 1336 solaims. (o1. 25o-127) This invention relates to an arrangement for occur in oscillographs whereby incorrect curves operating cathode ray tubes in which the deare obtained. l` ecting field and a magnetic focusing field per- According to the invention all these disad-4 r l meate each other. Such tubes are used, for invantages are eliminated by such an arrangement 2 A' 5 stance, as picture analyzers for television purof the circuit that variations of the deflecting and poses. Y l focusing fields'. caused by variations' of voltages If a magnetic focusing field for electron opare of the same phase and equal in percentage tical reproduction of,y for instance, a photo- The simplest way to realizev this idea consists in cathode in a Farnsworth'mage Dissector, persupplying all fields from 'one common voltage meates the deflecting fields, a rotation of v'the source, as, for instance,l a common power pack. direction occurs which depends upon the inten- It hasbeen found that a perfect compensation sity of the focusing field. This rotation which of Vall variations 'and interferences can be olo-v occurs in electrostatic as well as magneticdeflectained in this manner. The compensation is tionis caused by the fact that the electrons are based upon thefact that the angleof defiection l5 always influenced by the focusing field if they increases with increasing intensity of the de- 15l y have a component of -velocity transverse to the fleeting field, and that it decreases with increasaxis of the tube. Such a component-however, ing intensity of the focusing field. If the rotais generated in'deection and thus has an addition of the picture is 90 degrees, both effects comtional secondary deflection as a-consequencc. pensate each other. Forelectrostatic deflection.

'20 The rotation of the deflection direction vcauses perfect compensationisialso obtained lfor peri- .a rotation of the entire image which approaches odical intermediate values; f

a limit of 90 degrees with increasing intensity This invention has the advantage that `only of the focusing field, one. power pack with little filtering is required, When using magnetic deflection, the influence whereas so far each one of the power packs had y of the focusing field upon the direction of the to be extremely carefully filtered.

deflection furthermore causes av distortion of the Different circuits may be used for the realizaimage because the secondary deection does tion of the invention. The choice is partly de-Y not occur linearly. The distortion is made nopendent on whether the amplitude of the Kipp ticeable bythe fact that the coordinates of the oscillations depends upon the voltage applied to scanning field are no longer straight. the corresponding Kipp circuit or on the current. 30

Only if the intensity of the focusing field is of In the first case the Kipp circuit and the focusing such value that the rotation of the image is apcoil are connected in parallel, whereas in the proximately 90 degrees, does this distortion dissecond case a parallel as well as series connecappear. Thus, this is a requirement for a good tion is possible. In the case of parallel connecv image, because the intensity of the focusing field tion it is advisable to make the time constants of 35 is also, on the other hand, determined by the all branches equal.

dimensions of the tubefand by the accelerating The variations of the vfocusing field will natvoltage for the photoelectrons, these -values must urally also influence the sharpness of the image. also be adjusted to meet the above requirement. However, it has been found that this inuence is 4c Such arrangements have a certain disadvanslight and does not disturb the reproduced image 40 tage, in fact, the sensitivity depends upon the in any mannerintensity of the focusing field; thus, if the cur- The object of the invention may be more clearrent in the focusing coil varies, the angle of -de- 1y understood from the drawing, of which Figs-` flection also varies so that the image becomes 1 to 3 show several embodiments.

distorted.v Non-linear variations of the deflect- In Fig. 1 a power pack 2 is connected tojthe 45 ing fields also cause a distortion when the focuspower supply I. Direct current is taken from ing field' remains constant. If variations exist the points 4 and 5 of the power pack. A Farnsthey are harmonics or`sub-harmonics of the worth image dissector, indicated at 9, conscanning frequencies and standing distortion of tains a photocathode l2 and an anode I3. A

the image occurs. Other variations cause a focusing coil 6 covers the entire length of the l50` momentary flicker. In television transmission tube and secures electron optical reproduction.. these variations may, for instance, cause the Deflecting coils I0 and Il are provided through scanning lines to be sinusoidal instead of straight, which saw-tooth currents flow which are taken which considerably impairs the qualityv of the from the Kipp circuits 1 and 8 and which proimage. Corresponding interference may also duce deecting fields perpendicular tov each 55 other. According to the invention the focusing coil 6 as well as the Kipp circuits 1 and 8 are all connected to the .output of the same power pack 2.

Fig. 2 shows a similar circuit. The branches indicated by I and II each contain a Kipp circuit. The insuiciently filtered direct-current voltage is applied to the circuit I at the points I5 and I6. The Kipp condenser I8 is slowly charged through a resistor I I so that only a very small current flows. Block I9 schematically indicates an arrangement which consists of a discharge device for the condenser I8 and of an amplifier, the .output of which is connected with the picture frequency deflecting coil 2E). The arrangement IS corresponds to a very high resistance during the charge period, which is long compared with the discharge period and can thus be omitted for this time in the consideration. The time constant of this branch is thus equal to the product CR of the condenser I8 and the resistor I'I. The branch indicated by II represents an equivalent circuit for the line scanning arrangement in which the amplitude may be proportional to the current through the branch. The branch indicated by III is an equivalent circuit for the focusing coil. In both cases, the ohmic resistance of the branch is indicated by 22 and 23, respectively, and the inductance by ZI and 24, respectively. In order to accomplish the compensation of variations or interferences completely and especially independently of the frequency, it is advisable to make the time constants of the three branches equal; that means that L2 La lfl whereby L2, R2, and so forth, indicate the inductance and resistance, respectively, of the corresponding branches II and III.

Fig. 3 shows a third embodiment in which the Kipp circuits I and II, which are indicated by equivalent circuits, are connected in parallel and then in series with the focusing coil circuit III, which is also indicated by an vequivalent circuit. In this case the operation of both Kipp circuits is dependent on the passing current. A similar arrangement is also possible in which, however, one of the two Kipp circuits operates according to the applied Voltage.

In al1 cases the deflection can be produced by electrostatic as well as electromagnetic means. The invention is, of course, applicable also to television receiver tubes and oscillograph tubes.

Having thus described my invention, I claim:

1. In combination with a cathode ray tube, an electromagnetic focusing circuit, a deflecting circuit operable to influence an electron in directions normal to each other, and a common power supply for said focusing and deflecting circuits, said circuits having approximately equal time constants.

2. Apparatus substantially as set forth in claim l, wherein said focussing circuit and said deiecting circuit are connected in parallel.

3. Apparatus substantially as set forth in claim 1, wherein said focusing circuit and said deecting circuit are connected in parallel.

4. Apparatus substantially as described in claim 1 having a series connection between said focusing circuit, said deecting circuit and said common power supply.

5. In combination with a cathode ray tube, a cathode ray beam focusing circuit and a pair of deiecting circuits, all operable to influence an electron in directions normal to each other, said focusing circuit and said deecting circuits having time constants approximately equal to each other and being energized from a single power supply source.

HERBERT BHRING.

Images