US2224113A - Television apparatus - Google Patents

Description

Dec. 3, 1940. K. SCHLESINGER IYELEVISION APPARATUS Filed June 3, 1935 Una/anger:

" Patented Dec. 3, 1940 I TELEVISION PA TUS v .1 [Kurt Schlesinger, Berlin, Germany, assignor, by

i mesneassignmentato Lo eweRadio,Inc., acorv poration of'New York Application June s, 1933'; Serial No. 6741208 In G ermany June 7, 1932' 10 Claims. 01; it's-17.5)

. It is known for the urpo or simplifying the receiving arrangementtotransmitby the sender at the endof each line a short synchronising impulse, and at the end of each image along,

'5 synchronising impulse, theamplitude of which is greater than the maximum amplitude of the image potential; r

It has been proposed to separate this synchronising impulse at the 'receiving' end from the l image potential with-the assistance of a compensating potential supplied by-a counter-battery; which compensating potential acts' in opposition to the voltage mixture picked up and amplified by the receiving apparatus,- and which has at least to be equal to the' maxinmm image'potential andsmaller than the synchronising potential.

The use of a compensating potential of 'thi's na- 'ture for separatingthe synchronising- -impulse from the image potential isjdifflcultifthe fluc- 0- tuations in intensity" of the strength of" field at the receiver are considerable. 1

Further difiiculties arise; owing to the' fact that the absolute value ofthe"pctentials'receive'd 'va ries very greatlyat the receiver upon manipula V tion when means are provided forreg'ulating the"! contrast in the picture. The variable nature of the potentials rendersit necessary to make the H compensating potential-correspcndin j I The methods hitherto proposedem'ploy for'this 30 purpose the derivation of a mean-value, from the,

"rectified synchronising impulses it e, insuch a manner that to the-grid'of a special valve a nega' tive potential is given} which is proportional to the'average intensity'of the reception-and allows 35 only the amplitude-peaks; 1'; e. the 'synchroni'sing impulses to pass-to thesynchronising means.

Since; howeveryithe synchronising impulses in" a meanvalue is not 's'ufii'cient in allcases-to en 45 from the received voltages by theuse ofa variable regulating device, which-'is controlled by all the received voltages, and generatesa counter-poten tial, which allowsthe' passage merely of am'plitude" peaks,' i. e';,- the synchronising potentials.

. 50 Thesaid device consistsflof aseparatingfilter comprising a thermionic'valve'a'nda resistance in parallel therewith,,'inf connection with a condenser.

' V For carrying fo'utithemethod according to' the i 55 inventionipreferably an apparatusfor controlling v the movement-of the light rayis'fexnployed, for

the'control of which ver'ylow control potentials' (-upto approximatelyfi volt). are sufficient. An arrangement of this kind is described, forexample, in-application for Letters Patent of the 5 United: States, Ser. No 668,940,-fi1ed May 3, 1933;

' -The' invention will be more fully understood by reference to the appendeddrawing. "which in Fig;- 1 shows by-way' ofexample an arrangement for; carrying out the method accordingto, the invention, while Fig.2 is a detail; view-illustrating Y a modification and Fig.3 is a 'diagramhereinafter referred tofin explaining the operaticnof my:improved-televisionapp'aratus.- InFig. 1, I.

is thereceivingand arnplifying arrangement with apparatus 2 for regulating the contrast 'onthe' received picture By the said receiver and'amplifier, the potential mixture is conductedon the one hand-over the line '3 direct to the light controlapparatufsuor image reproducing deViceQpreL V I I er'ably a' Braun' tube, and o'n'the other handis passed o'n via the condenser 5 (of, for example, 7 v

10% pi), to thefcontrolling means. 6 is a diode with the hot cathode and theiano'de 241 ln'st'ead ofthe diode'an'y suitabletype o'f; 'electron 25 device, for instanc'e'amulti-electrode vaitemay glow-dischargej-tnbes';prefrably of that type in" Which'the starting of the c'u'rrent i s determined the grid p t'ential, butsi which the u rent- 7 interrupted On'IyYbyt ipl e oltage below its'criticalvalues The t'ubes Iii-and l'l'are provided With-the grids"?! an'd itfl; the] cathodes Z8 and 3| and the anodes--26 and 29'.- The anodes 26 and 29 are'jlinked up with the grounded positive" pole'of'the anode battery 8.

The cathodes are connected with the condensers 'M and l5; which are charged withthe assistance of the chargingtubes l8 andl'9. "During the charging the-potential of the cathodes is shifted 40 into negative. The gridofthe image'control tube l lis'v connected'through the'medium of the resistmice :1 z'and the condenser |3','-which are selected in such fashion-(for example attl-megohim and 1 niicrofa'radl thatthe highfrequency parts of the'po'tential mixturevincluding' the line synchronising' impulses ar'e' withheldfromthe grid, and through 'theim'e'dium' of-the resistance 9, which ln-iaybeselected" at approximately 5X10? ohms; with: a t'apping point of 'the battery 8,;which tap:

ping-point; of course, is'negative in relation tolthe positive pole-of 'saidbattery. To the same tapf ping' 'point there is connected over theline fliand theresistance 9 throughfthe resistance Ill and high frequency parts of the potential mixture and ingly, the synchronisation is wholly independent may be selected at approximately .1 megohm and 10 ,uf., the grid 2'! of the glow tube 16 of the line-control apparatus. The line-control potential is taken from the terminal 20, the imagecontrol potential from the terminal 2|. The value of the resistances l and I2 and the condensers l I and I3 may, generally speaking, preferably be such that the time constants r of the circuit I0, I! and 1- of the circuit I2, l3 are approximately -r 1O and 7 :10

In Fig. 1, I have shown heating filaments immediately below the cathodes of the tubes or valves 6, H5, l1, l8, and I9, and I have also indicated a heating battery, that is, a battery for supplying the heating current to the filament located below the cathode 25 of the tube or valve 6. It will be understood that the heating filaments of the other tubes or valves are similarly connected with a source of current.

The operation of the apparatus is as follows:

Whilst the anodes 26, 29 are at a constant positive potential the grids 21, 30 of the glow tubes l6, I! receive a strong negative bias in relation to the respective cathodes. The extent of the bias is determined by the tapping at the battery 8. Upon the charging of the condensers l4 and I5 by the charging tubes 18 and 19 the potential of the cathode 28 or 3| respectively is shifted into negative until the hot cathode has become negative to such extent that the blocking effect of the grid ceases and the discharge occurs. As described in detail below, the synchronising potential is conducted to the grid. By suitable selection of the grid bias it is possible to adjust the defleeting potential apparatus in such fashion that the same is capable of producing either both free as well as enforced relaxation oscillations, or merely enforced, i. e. synchronised relaxation oscillations. The latter case occurs when the negative grid bias is selected to be so high that the cathode is unable to reach the potential necessary for discharge. In this case discharge is only possible when the potential of the grid hasbeen shifted to the requisite extent into positive by means of additional potential (synchronising potential). According to the invention, the grid bias is preferably so adjusted that a very small variation in potential of the grid (approximately .1 to .5 volt) is quite sufilcient to produce a discharge. This additional synchronising potential is taken from the amplitude mixture with the assistance of the regulator B. The diode 6 acting as a variable regulator produces a counter-acting 1 direct potentiaLby which the negative parts ,of

the amplitude mixture are allowed to pass and the positive parts with the exception of the amplitude peaks of the synchronising impulses are cut off. A complete elimination of the peak potentials cannot take place, as the condenser charge flows off slowly overthe large leak resistance 9, so that the counter-potential produced by the variable regulator is at no time able to reach completely the value of the peak potential. The potential of the grid 30 upon the arrival of a long synchronising impulse, and the potential of the grid 21 upon the arrival of every (i. e., both a long as well as a short) impulse, will be shifted to a relatively small extent into positive. This slight displacement of the grid potential is suflicient, when using grid-controlled glow tubes, to control the tube and to synchronise the relaxation oscillations. The synchronisation is accordingly controlled by the peak potential independently of the absolute value of the same. Accordof the absolute value of the image or synchronising potential.

The leak resistance 9 must be sufficiently large to prevent the condenser charge from flowing off too rapidly. The condenser 5 on the other hand requires to be selected in such fashion that the variation in the absolute value of the potentials (contrast regulation or variation in the strength of field) is able to take place with sufficient rapidity.

The deflecting frequency may be varied in the manner known per se by variation of the condenser and of the charging current. This is easily accomplished when the valves [8 and I9 employed for the purpose of charging the condensers I4 and I5 respectively are screen grid valves as indicated in the drawing; I might, however, dispense with the screen grids and their connections, in which case the valves [8 and I9 would be diode valves of the same character as the valve 6.

As set forth in detail in the above, it is possible to adjust the grid bias in such fashion that the deflecting apparatus does not produce any free relaxation oscillations at all, and scanning is initiated only by the synchronising impulses. In many cases, however, it may also be desirable to select the potentials in such fashion that the apparatus is able to generate free relaxation oscillations, and that by reason of the synchronising impulses solely synchronisation of the apparatus takes place.

In further explanation of the principles of my invention, I will now refer to the diagram Fig. 3. It will have been understood from the foregoing description that the impulses reaching the receiver and amplifier I from the transmittter are a mixture of frequencies containing the frequency band of the image potentials and also the synchronizing voltages. In Fig. 3, the curve A represents a control potential of maximum amplitude, while curve B corresponds to about the minimum potential required for synchronizing purposes. For initiating the operation of the glow-discharge tubes I6, I! on the Braun tube or other image-reproducing device, the amplitude peaks of the curve must extend to a certain amount beyond (above) the'initiating line indicated at I in Fig. 3.

Under especially favorable reception conditions, the carrier wave may produce potentials such as represented by curve A, which lies en tirely above the initiating line and therefore would completely compensate the blocking efiect produced by the strongly'negativebias potential normally applied to the grid 21, 30 of the glowdischarge tubes l6 and I! respectively. This undesirable condition is remedied by my invention, according to which adjustments are made which will shift the position of the potential curveA into the negative region, that is to say, belowthe zero line indicated in'Fig. 3. The means employed by me for this'purpose, in the embodiments illustrated, consists of the regulating device comprising the condenser 5 and the valve 6 or 6, in conjunction with the resistance 9. This device operates as follows:

Whenghjghly positive impulses are received, as indicated by themaximum curve A,electrons are emitted from the cathode 25 of the regulating valve 6 or'6', which cathode is capable of emitting electrons abundantly. The result of such electron emission is to cause the anode 24 to receive a negative'charge of increasing strength. This negative charge-serves for varying the bias on the curve; B,'. located below the zero line. and. just reaching it; attheQamplitude peaks, although it is not essential that; such peaks should reach the zeroline, as: long; as they'exceed the. initiating line-I. The necessarybiasis thus obtained at the grids 215,530. Int'this,.:manner I: have provided a self-regulating device which controls the amplitude' of the synchronizing. frequency to such an; extent that at every i moment the initiating impulse will be determined exactly as to time and 9-mplitude.-,

. It has .beenascertained: that. when, employing glow tubesjoikthe grid type; it is necessary to screen off-,completelythe entire deflecting device. It'has-beenfound desirable to again .screen off separately within the, screening container all leadsconductingfluctuatingpotentials.

As; regardsgthe method accordingv to the invention,it-'is particularly convenient .toemployglow lamps of-thegrid type. in accordance with the alcove -application No.1 668,940, having indirectly heated, metallic-vapounf high-emission cathode, argon or nitrogen filling of approximately .1 to 10 ,mmgpressure, extremely, low reciprocal of the amplification factor, and. tungsten electrodes. Naturally, the method according to the invention may also be performed with other suitable discharge tubes.

The arrangement according to the invention may be employed'in connection with all known control frequency methods. Since when making use of glow lamps of the grid type currents may be produced of almost any desired value, the arrangement may naturally also be employed for the operation of mechanical systems, for example Y those systems which operate with synchronising motors or the like. I

As I have stated above, a'multi-electrode valve might beemployed instead of the diode 6. Such an arrangement is indicated in Fig. 2 showing a valve 6' which inaddition to the anode24 and the hot cathode 25 includes a grid 6". In this case the condenser 5 is connected with the, grid 5'', the other connections being the same as in Fig. 1. I

I claim: p

1. In a television reception apparatuscomprising areceiving amplifierhaving an output terminal adapted for connection with an image reproducing device, a gaseous discharge relaxation oscillation generator having means adapted forconnection with said image reproducing device, a voltage source and means to connect said high voltage source with said generator, a condenser, a hot-cathode valve, the one electrode of said condenser being connected to the output terminal of said amplifier and'the other electrode to an electrode of said valve other than ing a receiving amplifier having an output terminal adapted for connection with an image reproducing device, a gaseous discharge relaxation oscillation generator having. means adapted for connection withs'aid imagesreproducing.device, a voltage source andim'eanstoconnect said voltage sourcewith said. generator; a condenser, a" hotcathode valve including a. plate and a grid, the oneelectrode of said'condenser being connected to the output terminal ofsaid amplifier and the other electrode tothe grid of said-valve, aconnection from the plate of said valve to the input terminal of said generator, a connection between the plate andthe.cathode oifisaid valve, a resistan'ce included in the last-mentioned connection, and a directcurrentconnection from said' cathode tov a negative. point'tofsaid voltage source.

3. In a television reception apparatus-comprising. areceiving amplifier having'anoutput terminal adapted .for. connection Withan imagereproducing. device, la-relaxation oscillation. generator having: means adapted. for connection with said image reproducing device, a voltage source and means to connectsaid voltage source with saidgenerator, at condenser; a hot-cathode two-electrode-valve comprising 'aplate and'a cathode,

the one electrode. of said condenser being'connected to the. outputyterminal of said; receiving amplifier and the other electrode to said plate of said valve. and to the input terminal of said generator and to said cathode, a resistance included in the connectionbetween saidother condenser electrode and saidcathodaand a connection from said cathode to a negative 'point of said voltage source.

4. In a television reception apparatus comprising a receiving amplifier having a terminal adapted for connection with animage reproducing device, an anode voltage source, a relaxation oscillation generator comprising a grid-controlled v glow tube, a condenser connected with 'saidtube and meansconnected with said tube and said condenser, for chargingsuch condenser and producing the relaxation oscillation voltage, means for connecting the cathode of said glow tube with said reproducing device, the plate of said glow tube being connected to said anode, voltage source, the one electrode of said condenser being connected to said plate and the other electrode being connected to the cathode of said glow tube and to said relaxation oscillation voltage producing means, a further condenser, a valve having a hot cathode and a plate, a resistance, theone electrode of said last-mentioned condenser being connected to the output terminal of said receiving amplifier and the other electrode to the plate of said valve, a connection from said plate to the grid of said glow tube, another connection from said plate to one point of said resistance, a connection from another point of said resistance to the cathode of said valve, and'a connection from said cathode to a negative point of said anode voltage source.

5. apparatus according to claim 4, in which the capacity of the condenser connected with the valve is of the order of 10- microfarads,

. and in which the resistance connectedwith said valve is of the order of 5x10 ohms.

6. An apparatus according to-claim 4, in which a screen grid valve is employed as the means for charging the condenser connected with the grid-controlled glow tube.

7. In a television reception apparatus comprising a receiving amplifier having a terminal adapted for connection with an image reproducing device, an anode voltage source, a relaxation oscillation generator, comprising two grid-controlled glow tubes for producing line and image deflecting voltages respectively, a condenser for each of said tubes, a valve associated with each of said tubes and condensers for producing the relaxation oscillation voltages, the plates of said tubes being connected to said anode voltage source, the one electrode of each said condensers being connected to said plates and the other electrode of each being connected to the cathode of the respective tube and to the plate of the respective Valves, 2. further condenser, a hotcathode valve and a resistance, the one electrode of said further condenser being connected to the output terminal of said receiving amplifier and the other electrode tothe input of said hot-cathode valve, a connection from the plate of said valve to the grids of said tubes, another connection from said plate to one point of said resistance, a connection from another point of said resistance to the cathode of said hot-cathode valve, and a connection from said cathode to a negative point of said anode voltage source, and means for connecting the cathodes of said tubes with said reproducing device.

8. An apparatus according to claim 7, in which screen grid tubes are employed as the tubes associated with each of the grid-controlled glowtubes and their condensers for producing the relaxation oscillation voltages.

9. In a television apparatus comprising a receiving amplifier and a relaxation oscillation generator for producing the cathode-ray deflecting currents, said generator including an electronic tube provided with a grid, a source of electricity connected with said generator and having a tap connected with said grid to supply a biasing voltage, and a regulating device comprising another electronic tube, such last-mentioned tube having an anode and a cathode, said cathode being connected to the above-mentioned tap, and said anode being connected to the grid of the generator tube, the tube of the regulating device being also connected with the output of said amplifier.

10. In a television apparatus comprising a receiving amplifier and a relaxation oscillation generator for producing the cathode-ray deflecting currents, said generator including anelectronic tube provided with a grid, a source of electricity connected with said generator and having a biasing tap connected with said grid, and a regulating device comprising another electronic tube, such last mentioned tube having an anode, a cathode, and a third electrode, a condenser the terminals of which are connected with said third electrode and with'the output of said amplifier respectively, the cathode of the last-mentioned tube being connected to the above-mentioned tap, and the anode of said tube being connected with the grid of the generator tube.

KURT SCHLESINGER.

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