Патент USA US2404173код для вставки
July 16, 1946. J. A. HANSEN 2,404,173 , TELEVISION SIGNAL GENERATOR Filed July‘ 5, 1941 VIDEO FREQUENCY AMPLIFIER TELEVISION TRANSMITTING APPARATUS 0.. VIVS\NA L v I? <5 523 FIELD SCANNING GENERATOR TIMING GENERATOR GENERATOR ' INVENTOR JOHN A. HANSEN BY ATTORNEY I; of Patented July 16, 1946’ 2,404,173 ; UNITED‘ STATES PATEN '1" OFFICE . 2,404,173 , TELEVISION SIGNAL GENERATOR John A. Hansen, Bayside, N. Y., 'assignor, by'mesn'e assignments, to Hazeltine Research, Inc., Chi cago, 111., a corporation of Illinois Application July 5, 1941, Serial No.‘401,'080 8 Claims. 1 (C1. 178-172) This invention relates to television signal gen erators and, particularly, to television signal gen craters of the type including a cathode-ray tele vision signal-generating'tube. - The operating characteristics of television signal generators of the type which includes a cathode-ray signal-generating tube vary rather critically with the value of the tube 2 pl’itude of. these spurious pulses varies with the magnitude of the beam current of the tube and that a suitable control effect can be derived therefrom to control the beam current in the de ' sired manner mentioned above. It is an object of the present invention, there fore, to provide an improved television signal gen erator vof the type including a cathode-ray sig beam current. Speci?cally, the shading e?ect nal-generating tube which is not subject to one characteristic of tubes of ‘this type and the 10 or more of the above-mentioned disadvantages sensitivity of such a, signal-generating tube of television signal generators of the prior art. vary with variations of the beam current of It is another object of the invention to provide the tube. Many factors, such as a variation an improved television signal generator includ of the unidirectionalv supply potential, changes ing acathode-raysi‘gnal-generating tube in which in temperature, etc., may cause. the beam ‘cur-' 15 the beam current of th'etube-is maintained sub rent of the‘ tube to vary. In‘. a conventional television transmitter which includes a tube of stantially constant'during trace scanning periods the type under consideration; it ‘is customary to In ‘accordance with the invention, a television‘ signal generator comprises a cathode-ray tele provide a manual control for the beam current ’ of the signal generator. ' of the signal-generating tube and it. is necessary 20 visiorr signal-generating tube including a source for the operator to vary the adjustment from of beam current and a beam-control electrode time-to-time to maintain a value of beam current and means for‘ deriving. a signal output from the which provides most satisfactory operation. tube which includes video-frequency television Since the value of beam current for optimum signal components and spurious periodic pulses sensitivity does not usually correspond to that of larger amplitudethan the television signal giving minimum shading effect-sin practice, it is components, which pulses vary in amplitude with customary to adjust the beam. current to that variations. of. the beam current. The signal gen~ value which provides a reasonable compromise erator of the invention also comprises means re‘ between the shading e?ectfln the signaioutput sponsivev primarily to the periodic pulsesfor de and maximum sensitivity. However; in some 30' riving a unidirectional control effect and means television signal transmitter installations it is for utilizing .the control effect to maintain the‘ necessary to leave the transmitters unattended. beam. current of the signal-generating tubesub It is particularly desirable, therefore, to provide stantiallyv constant during trace periods of the an arrangement for automatically maintaining signal generator.‘ I a predetermined optimum'value of beam current For a better. understanding of the invention, in a cathode -ray television ‘signal-generating tube together with otherwand further objects thereof, independent of variations in operating conditions. reference is had- to the following description. It is well known that the output signal of a taken ‘in connection with the accompanying draw~> television signal-generating tube vof the type un— ing and. its scope will be pointed out in the ap der consideration includes spurious pulses which 40 pended claims. are generated due to any sudden changes in the ' The single ‘?gure of‘ the drawing is a schematic beam current, which changes may be caused, for diagram. of a complete television transmitting example, by spot-translation velocity changes or by the fact that the beamtravels from the pho'-“ tosensitive target to the nonphotosensitive mar gin or backing plate‘ of the target‘, as weilas the desired video-frequency television signal. com ponents developed by light from the object't'o be, televised and incident on the photosensitive ele ments of the mosaic. The spurious pulses in't'hev output signal of the tube have an amplitude which is many times that of the desired video-frequency‘ television signal components and frequencies cor~ responding to the line-scanning and ?eld-scam ning frequencies. It has been found-that. the am 55 > . system including a television signal generator in accordance with the invention. . Referring now more particularly to the draw ing, the television transmitting system repre sented. includes a‘ conventional camera or pro jector 1'0" and a cathode-ray tube II. This tube comprises ‘an elongated envelope l2 including a cylindrical end portion or neck and an enlarged end portion. ’ In the neck of the tube l I there are disposed a source of beam current such as a cath ode IS,‘ a beam-control electrode I 6, a ?rst anode H, a second anode“! and a collector electrode “3a. in‘ the order named, these electrodes c0n~ 2,404,173 3 , . l, : ' . ‘1 ‘J- \ Ti 4 I ~ . antenna system 32, 33 in a conventional manner. ; stituting what is conventionally referred to in l Line-synchronizing pulses and ?eld-synchroniz I‘ the art as an electron gun. The collector anode 18a preferably comprises a metallic ?lm or coat ing pulses developed in timinggenerator 23 and applied to transmitting apparatus 3|’ are also modulated upon the. carrier signal for transla tion with the video-frequency signal generated ‘ ing on the inner ‘surface of the envelope l2; as 5 shown. A photosensitive target I9 is disposed in i the enlarged end portion of, the tube. The target in tube ||. ' » may be constructed in a conventional manner and ' i ,Co'ming now'tq-the portion of the system con _ ‘ include athin sheet .of dielectricirnaterial‘, such‘. i stitutin'g the- present invention-‘,iin order to derive as mica, having atransparent metallic coatin'g'ror'i ' signal :plate facing the camera Ill, and a photo . ~ 10 a normal operating bias 'for signal-generating sensitive mosaic front surface of suitable ma-fi ' tube H, there is provided a duplex recti?er 39 including cathode 40 and anode 4| for rectifying a'signal ‘output ‘from line-scanning ‘generator 2|. l-terial, such as a silver-caesium-oxygen mixture ‘ Q‘ or compound, thereby providing, in effect, a mull" The signal input for diode 4|], 4| derived from titude. of minute“"éondensers,having the signal _. _ plate as a common electrode. Suitable operating ‘1.5". line-scanning generator 2| is' applied thereto throughrcondenserllt and load resistors 43 and potentials are supplied to the several electrodes ‘ of tube H from a source of-unidirectional oper --44 connected in. series. Resistor 44 is by-passed " by a condenser 45 while resistors 43 and 44 in. series are by-passed by a condenser 38. The di the drawing a line-scanning generator 2| and 20 rect current path for diode 4|), 4| is completed by means of a resistor 46 connected between cath a ?eld-scanning generator 22 which are timed by ating potential, such' as a battery '20; ' ‘ " " ‘ There are also provided'i'n the transmitter‘. of ‘ ode 40 and ground. The voltage developed across resistor 44 is applied as an operating bias to the control electrode I6 of tube I! through a resistor l a timing generator 23 and whichhave their out put circuits connected to de?ecting plates 25 and 25hr tube II, respectively. "The output circuit ' of tube || include'sa load resistor28 connected 25 Hand .a resistor 48 in series. In order to, derive a control e?ect which varies to. the signal plate of target .|9 through'a cou primarily with the spurious periodic pulses gen pling condenser j29 and to a conventional video-n erated inv tube ||,Itube 39 includes a diode 50, 5| frequency ampli?er 3B’ of one or, more stages,‘ coupledrto the output circuit of video-frequency which, in turn, is coupled to a conventional tele ampli?er 3|! through‘ av coupling condenser 52, a ' vision ‘transmitting apparatus, indicated gen erally at 3|, andterminated in an antenna sys condenser 53 coupled in‘ parallel with resistor 41,. chronizingr signals‘ are also applied from timing vided for diode 50, 5| which includes resistor 41 and a resistor 55; the. inclusion of resistor 41. in and a condenser 54., A direct current path is pro tern33, 33. Line-synchronizing and'?eld-syn generator 237 to the television transmitting ,appag ratus 3| for transmission with,_the video-free , the. load circuit of diode 50, 5|.provides a means for utilizing the control effect derived from diode so, 5| to maintainithe beam currentof'tube || substantially constant during .Ytrace periods of quency :signalgenerated intube |,|._. Y ‘ The apparatus just describedjn general, rep resents _a conventional television transmitting systemrand, the'construction and operation of such apparatus, being well known in the .art, _a detailed description thereof is unnecessary here: the signal-generating tube ll. 40, in., In brief,’ however,’ inrthe operation, of. the ‘ apparatus described,.imagesjof ,theisceneto'be; transmittedare projected by the camera It on. . , In ordertocutoff the beam current of tube H, during ?eld-retrace scanning periods, periodic, .‘ pulses are derived/from ?eld-scanning generator 2.2 and. applied through a condenser 51 to beam-V, control-electrode |6.‘_ . . . , I‘ the mosaic surface of target T|9 effectingphotoj-z 4.5.; .In consideringthe operation of the circuit just emission by ‘the various mosaic elements in 3.01‘, cordanoe. withthe light intensity at. theVcorre spending elements of the, image'being transmit-: ted; __Electrons are generated, vaccelerated/and developed into abeam bythe electron gun come‘; prising elements |5-+-| 8, inclusive, the beam being‘, focused on the target l9 and causingsecondarye. electron emission byv the elementary mosaic ele-. described, it wilLbeseen. that an output from lineescanning.generatorll’ is recti?ed by diode > 4.8, 4| to provide across the load circuit thereof ‘ includingresistors 43, '44, a sourceof unidirec tional voltage which is negative. with respect to ground. The :portion of this voltage across resis tor.44.is applied through resistor 41 and isolating resistor48, tothe- beam-control electrode l6 of tube. »| Lto provide a. suitable normal negative op ments of a value varying in accordance .withits. potential as determined byits photoemission dur 55: erating bias for the. beam-control electrode l6 of the tube. However, this bias voltage is substan ing the preceding scanning. cycle. Potentials of tially, constant and, unless other precautions were saw-tooth wave form, generated by the.genera-. taken, thebeam current of tube || would. vary tors 2| and 22, are applied to the scanning plates with variations. in operating conditions, as. de 25 and 26, respectively, thereby producing electro-. static ?elds which de?ect the beam in two direc-j 60 scribed above, thereby necessitating a manual adjustment ..of1the beamcurrent to an optimum tions'normal to each other, causing it to ,scan‘ valuesuch that satisfactory sensitivity and min ‘?elds or series of parallel lines on'the targetQin imum. shading characteristics areimparted to the usual manner. , The secondary. electrons which are emitted from the mosaic elements are the tube,.||. .. ‘ _. I. . ' L ; collected by the collector electrode |Ba.v Voltages 65 ~ Inasmuch as .the signal output from tube | I which is. amplified by ‘video-frequency ampli?er‘ are thereby developed at the backing plate ‘of 3|!- includes, .in addition to, the‘. desired video-fre quency television components, spurious periodic signals. of. larger amplitude than the television resistor 28, a video-frequency voltage which varies. with variations in light and shade in the succes-g -7-0 signal.;components, as mentioned abovewhich spurious signals vary in amplitudeywith variations sive incremental areas of the scene to be trans: of the beam current of the tube, these spurious mitted. This video-frequency voltage is ampliy. ?edin the video-frequencyvampli?er 3iirand is. pulses can beutilized to control the beam current utilized in the transmitting apparatus 3| tomod-H of tube |l_ to; maintain it at‘ any preselectedop target 19 which,’ in turn, cause to be developed in'the output circuit of tube H, which includes ulate, a carrierwave. fvhieh is broadcast iron; the‘ 75 tirnum operating value. __ The. circuit 4]., 5.3. of . 2,404,173" 5 > ,6 recti?er 50, 5| is given such a time constant that and modi?cations as fall within-the true spirit it operates as a peak recti?er for developing in the load circuit 41, 55 a voltage or control effect and scope of the invention. What is claimed is: 1. A‘television signalgenerator comprising, a which varies with the peak value of these spurious pulses and, inasmuch as'the resistor 41' is in cathode-ray television signal-generating tube in‘ > cluding a source of beam current and arbeam- v eluded in series in the'grid-cathode path of tube ~ II, the portion of this voltage developed across control electrode, means for deriving a’ signal resistor 4'! serves to control the beam‘ current output from saidv tube including video-frequency‘ of tube H. By proper selection of circuit con-v television signal components and. spurious peri stants, this control voltage may be made effective 10 odic pulses of larger amplitude than said televi to maintain the beam current substantially con sion signal components which pulses vary in am stant during trace periods of tube lil. rlJhe time plitude with variations of said beam current, constant of the circuit is preferably not apprea means responsive primarily to said periodic pulses ciably shorter than the ?eld-scanning period of for deriving a unidirectional control effect, and the systemand may be, for example, only slightly 15 means for utilizing said control effect to main greater than the ?eld period; tainr'sa'id beam current substantially constant dur ing' trace periods of said signal generator. ' The pulses derived from ?eld-scanning genera tor-2,2 and applied through condenser 5'! to the 2. A television signal generator comprising, a cathode-ray television signal-generating tube in beam-control electrode l6 serve to cut off the beam current during the ?eld-retrace periods, in 20 cluding a source of beam current and a beam a manner which is well understood by those skilled in the, art, to avoid the appearance of control electrode, means for deriving a signal output from said tube including video-frequency spurious lines in they reproduced image. If the television signal components and spurious peri tube beam current is not cut oil during ?eld~ odic pulses of larger amplitude than said televi retrace periods the charge pat-tern on the mosaic 25 sion signal components which pulses vary in am is ‘disturbed in such fashion that a record of the plitude with variations of said beam current, a spot path during retrace remains on the mosaic recti?er responsive primarily to said periodic for some portion of the ensuing traceperiod. pulses for deriving a control potential, and means During the ensuing trace period this disturbed for utilizing said control potential to maintain said beam current substantially constant. during condition of the mosaic is translated into a nor mal television signal which is then reproduced by the picture of the system. It will be under ' trace periods of said signal generator. 3. A television signal generator comprising, a stood that this feature of the circuit can be omitted, if desired. While applicant doesnot intend to be limited to any particular circuit design, there follows a tabulation of design information which has been cathode-ray television signal-generating tube in- ‘ cluding a source of beam current and a beam 35 television signal components and spurious peri odic pulses of larger amplitude than said televi sion signal components which pulses vary in am plitude with variations of said beam current, a peak recti?er responsive primarily to said peri odic pulses for deriving a control potential, and found to be particularly useful in practicing the invention: Tube ll __________________________ __ Type 1847 Tube 39 __________________________ __ Type 6H6 Resistor l3 _________________ __megohms__ Resistor 28 _____________________ __do_____ Resistor 43 ___________________ __kilohms__ Resistor 44 _________________ __megohms__ 10 2.2 100 means for utilizing said control potential to main tain said beam current substantially constant dur ing trace periods of said signal generator. 1.5 45 4. A television signal generator comprising, a Resistor 46 ___________________ __kilohms__ Resistor 41 __________________ __megohm__ Resistor 48 _____________________ __do____ 250 1 1 Resistor 55 ___________________ _gkilohms" 220 Condenser Condenser Condenser Condenser Condenser Condenser 250 50 29 38 42 45 52 53 control electrode, means for deriving a signal output from said tube including video-frequency cathode-ray television signal-generating tube in cluding a source of beam current and a beam control electrode, means for deriving a signal output from said tube including video-frequency television signal components and blacker-than black spurious periodic pulses of larger amplitude than said television signal components which pulses vary in amplitude with variations of said beam current, a peak recti?er responsive primarily to said periodic pulses for deriving a unidirectional control potential, and means for "utilizing said control potential to maintain said beam current substantially constant during trace ______ __micro-microfarads__ _____________ __microfarad__ 0.01 ______ __micro-microfarads__ 500 _____________ __microfarad__ 0.1 _________________ __do__‘____ 0.002 _________________ __do______ 0.1 55 Condenser 54 _________________ __do ____ __ 0.25 Condenser 51 ______ __micro-microfarads__ 500 Line-scanning frequency _______________ __ Field-scanning frequency ______________ __ 2000 10 It will be understood that an average recti?er can be used in place of the peak recti?er 50, 5| and that, if a peak recti?er is used, it can be 60 periods of said signal generator. 4 5. A television signal generator comprising, a cathode-ray television signal-generating tube in cluding a source of beam current and a beam caused to be responsive to the peaks of the signal control electrode, a ?eld-scanning means for said of either polarity although the recti?er is pref 65 signal-generating tube, means for deriving a sig erably made to be responsive to peaks of the sig nal output from said tube including video nals which correspond to light values which are frequency television signal components and blacker than black. spurious periodic pulses of larger amplitude than While there has been described what is at said television signal components which pulses present considered to be the preferred embodi 70 vary in amplitude’ with variations of said beam ment of this invention, it will be obvious to those current, means responsive primarily to said skilled in the art that various changes and modi periodic pulses for deriving a unidirectional con ?cations may be made therein without departing trol effect and including means for eliminating from the invention, and it is, therefore, aimed variations in said control effect at the frequency in the appended claims to cover all such changes 75 of said ?eld-scanning means, and means for 2,404,173 7 ‘ utilizing said control e?ect to maintain said beam current substantially constant during trace 1 periods of said signal generator. 6. A television signal generator comprising, a cathode-ray television signal-generating tube in cluding a source of beam current and a beam control electrode, a ?eld-scanning means for said 3 signal-generating tube; means for deriving a sig nal output , from said tube including video 'frequency television signal ''components- and spurious periodic pulses of larger amplitude than 3 said television signal components which pulses vary in amplitude with variations of said beam current, means responsive primarily to said periodic pulses for deriving a unidirectional con trol e?ect and including a recti?er and a load circuit having a time constant not appreciably 1 shorter than the period ‘of said ?eld-scanning‘ means for eliminating variations in said control e?ect, and means for utilizing said'control effect to maintain said beam current substantially con 8 spurious periodic pulses of larger amplitudethan saidrtelevision signal components which pulses ‘vary in amplitude with variations of said beam current; means responsive primarily to said periodic pulses for deriving a unidirectional con trol potentiaLand means for applying said con trol potential to said electrode in series with said bias potential to maintain said beam current sub stantially constant during trace periods of said signal generator. " 8. A television signal generator comprising, a cathode-ray television signal-generating tube in cluding a source of beam current and a beam-, control electrode, a ?eld-scanning generator for said tube, means for deriving a signal output from said tube including video-frequency television sig nal components and spurious periodic pulsesof larger amplitude than said television signal com ponents which pulses vary in amplitude jwith variations of said beam current, means responsive primarily to said periodic pulses for deriving a unidirectional control e?ect, means for utilizing stant during trace periods of said signal genera said control effect to maintain said beam current tor. ‘ substantially constant during trace periods of said ,7. A television signal generator comprising, a cathode-ray signal-generating tube including a 25 signal generator, and means for deriving blocking pulses from said ?eld-scanning generator and source of beam currentand a beam-control elec applying them to said beam-control electrode to ' trode, means for applying a unidirectional op cut off the beam current of said tube during ?eld; erating bias potential to said electrode, means for retrace periods of said scanning generator. deriving a signal output from said tube including ' video-frequency television signal components and 30 JOHN A. HANSEN.