US2096985A - Television - Google Patents

Description

@c&. 26, 13.937. M. VON ARDENNE 2096985 TELEVISION Filed April 27, 1932 1 ;IF m W Q Patented Oct. 26, 1937 UNITED STATES PATENT OFFICE TELEVISION Manfred von Ardenne, Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe, Berlin- Steglitz, Germany, a company o! Germany Appllcation April 27, 1932, Serial N0. 607,720 In Germany April 29, 1931 2 Claims.

1 scanning is varied, viz. dependent on certain properties of the picture element to be transmitted, and preferably the light intensity thereof. II; is,

for example, possible when scanning an image line by line to regulate the rate of scanning by the intensi-ty.

An arrangement of this natura is illustrated in Fig. 1, while Figs. 2, 3 and 4 illustrate further modifications described in detail hereafter. In Fig. l, l is a film, which it is assumed is advanced line by line in a direction vertical 110 the plane of the drawing. 011 thls film there is reproduced through the medium of a lens 2 the fluorescent spot moving on the screen 3 of a cathode ray tube 4. This tube possesses a cathode 5, a Wehnelt cylinder 6, an anode I and a pair of deflecting plates 8. Behind the film I there may be provided a mal; screen 9, so that the ray of light passing dlfiusely through the same controlsa photo-cell III. The photo-cell current is amplified by an amplifier II, and controls the valve I 2, through the medium of which the condenser I3 situated in parallel with the pair of deflecting plates 8 is charged by the potential source I I. In parallel with the condenser I3 there is a glow lamp I5, through the medium of which, when its ignition potential has been reached, the condenser I3 is discharged, whereby the scanning of the line commences afresh. In this manner the same image appears on the screen 3 of the valve 4 which was scanned on the film I, either as positive 01' negative dependent on the polarity.

II: is now of considerable importance to employ a modulation resistance, o1 a modulation resistance in a circuit, in which the reslstance of the modulated element is independent of the conditions of the circuit to be modulated. The circuit described above possesses, for example, the disadvantage that for the purpose of maintaimng the characteristic of the charging tube I2 the alternating charging potentlal requires to be increased artificially. According now to the invention, the condenser I3, in order to avoid this, is charged through the medium of the relatively constant internal resistance of a tilting apparatus supplying a saw-tooth potential, whereby the charging operation is retarded by a photo-modulated multiple electrode valve situated in parallel with the condenser I3. By employing a parallel tube of this nature the maximum potential occurring in the system is equal to the deflectingpoten- 5 tial at the edge of the line. A n arrangement of I;his natura is illustrated in Fig. 2. Although in thls case the resistance of the modulating element depends on the conditions of the circuit I;o be 'modulated, the influence exerted is nevertheless a much smaller one. In this case ii: is of particular advantage to employ valves having a small reciprocal of the amplification factor, for instance screening grid. valves. Although in this case there is also the possibility cf compensating the potential Variation, an approxlmate solution (v alve with small reciprocal of the amplification factor) is nevertheless more simple and therefore to be preferred. As more clearly set forth in the following, a modulation of this nature is preferably obtained by intensity-modulated Braun tubes in which the pairs of plates to be employed as the modulated resistance result in a resistance, which from a practical standpoint, is independent of the conditions of the circult be modulated.

In Fig. 2 similar elerhents are furnished. with like reference charactersto Flg. 1. In this case the condenser I3 is charged by the battery I4 through the medium of a saturated. diode IG especially with ionic discharge. II; is necessary to employ a saturated ionic valve in orcler I;o obtain a linear charging cu1ve of the condenser. The charging of the condenser is retarded by the parallel tube I! controlled by the amplifier I I.

In the case of television apparatus such as described up to now lt is necessary to link the Image defiection with the line deflection by means of a line counting mechanism. The device hitherto 'employed for thls purpose is of a relatively complicated Kind. It hs been found that it is 40 sufiicient to allow two generators for the line and Image frequency, which are independent in themselves, 1:0 be acted upon by the same line modulator. Gare merely requires 1:0 'be taken that the image potential is modulated 130 a smaller 45 degree than the line potential.

A modulation of imageyand line slmilar to this is performed in the case of the arrangement according to Fig. 3. This figure corresponds with Fig. 2, whereby, however, there is added the con- 50 trol of the image potential. This is effected by means of the tilting apparatus I8, which in slmilar fashion to that for the line potential, may consist of a potentlal source, a saturated diode, a charging condenser and a glow discharge space. 55

The saw-tooth tilting potentlal o! this tlltlr'1g apparatus Is located at the lmage-deflecting plates I9. Intermediate line-by-line actuatlon of the .tllm l Is now omitted. In plane of this the film Is aclvanced Image by Image. The Image potentlal is modulated by the tube located in parallel with the charging condenser.

structed In the form of screening grid valves, In order 1:0 reduce the Influence of fluctuatlng anode potential to a minimum.

ThIs, however, is to be accomplished with the greatest advantage II. the llne and Image potentials are modulated by a Braun tube. The method of carrying this Into practlceis Illustrated In Fig. 4. In this case 2l and 22 are 1Ine or Image tilting apparatus, the potentlals of whlch are applled to the deflecting plates of the Braun transmission or receiving taube. The irmrease in potential Is modulated by an additional Braun tube 24, the deflecting plates of which a.re parallel 120 those of the first Braun tube. The modulatlon occurs by reason of the intenslty controlled flow of electrons between the pairs of deflectlng plates 25 and 2G, for instance by varlation 015 the potential o1 the Wehnelt cylinder 21 of thls tube. For the purpose of obtaining an efi'ective modulation the pairs of deflecting plates 25 and 26 are Set so close together that the fluctuating flow of electrons through the pairs of plates provides the modulation of the Image and line potentials. The degree of-modulation ls adjusted by sultable internal resistances of the Image and line tilting apparatus. The use 015 the Braun tube as couductlvity modulator has the appreclable advan tage that the conductivitles between its pairs of plates are, from a practical standpoint, wholly indepenclent of the conditions of the clrcult to be controlled.

I clalm:

1. In a televislon transmisslon device compris-- Ing a Braun taube hsiving cathode, anode, deflect- Ing means and a fluorescent screen, means for developing a cathode ray, a generator for produc- As already stated above, the valves I1 and 20 are preferably con- Ing deflectlng voltages 02 saw tooth wave form connected to seid deflecting means, a photo cell, a modulator resistance connected to sald photooell and In parallel to said generator, said reslstance serging for modulatlng said deflectlng voltages proportional to the photo cell voltages VaryIng with the llght falllng upon said photo cell, sald reslstance being approxlmately independent 015 the working condltions of said deflect- Ing voltage generator and said deflectlng means, sa.id resistance being constituted by the shunt resistance of two plates o1 a second Braun tube, comprising cathode, anode, two condenser plates and light Intensity control means connected to sald photo cell, the varying value o! sald resistance be1ng determined by the strength of the cathode ray passing through said plates of sald second Braun tube.

2. In a television transmission device comprls- Ing a Braun tube having cathode, anode, deflect- Ing means and a fluorescent screen, means for developing a cathode ray, two generators 1or pro- -duclng deflectlng voltages 015 saw tooth wave form, one for llne deflection and. the other one for Image deflection, connected to sald deflectlng means, a photo cell, two modulator resistances, each connected to said photo cell and in parallel 1:0 each of seid generators, said resistances servlng for modulatlng each sald dellectlng voltages proportional to the photo cell voltages varylng with the llght falllng upon said photo cell, said resistances being approximately Independent cf the working conditions 015 sald deflectlng voltage generators and said deflectlng means, said resista;n ces being constituted by the shunt reslstances of two palrs of plates of a second Braun tube, comprisixig cathode, anode, two pairs of condenser plates and light intensity control means connected to Sald photo cell, the varylng value of said resistance being determined by the strength of the cathode ray passing through sald plates of said second Braun tube.

MANFRED vor: ARDENNE.

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