US2166712A - Television system - Google Patents

Television system Download PDF

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Publication number
US2166712A
US2166712A US750055A US75005534A US2166712A US 2166712 A US2166712 A US 2166712A US 750055 A US750055 A US 750055A US 75005534 A US75005534 A US 75005534A US 2166712 A US2166712 A US 2166712A
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United States
Prior art keywords
picture
signals
cathode
ray
tube
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Expired - Lifetime
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US750055A
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English (en)
Inventor
Alda V Bedford
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RCA Corp
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RCA Corp
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Filing date
Publication date
Priority to BE411923D priority Critical patent/BE411923A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US750055A priority patent/US2166712A/en
Priority to FR793594D priority patent/FR793594A/fr
Priority to GB27805/35A priority patent/GB463967A/en
Priority to DER94572D priority patent/DE767558C/de
Application granted granted Critical
Publication of US2166712A publication Critical patent/US2166712A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/80—Camera processing pipelines; Components thereof
    • H04N23/81—Camera processing pipelines; Components thereof for suppressing or minimising disturbance in the image signal generation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/40—Circuit details for pick-up tubes

Definitions

  • My invention relates to television systems and particularly to television systems of the type in which a cathode-ray transmitter tube is em-
  • a picture appearing at the receiver usually is too dark in certain areas and too light in other areas.
  • one corner of the picture may be of a very dark shade while the corner diagonally opposite may be of a very light shade. This is commonly referred to as black spot.
  • black spot This is commonly referred to as black spot.
  • An investigation has shown that this is mainly the result of a characteristic of the cathode-ray transmitter tube.
  • the use of alternating current lighting for illuminating the object to be transmitted causes a hum component to be superimposed on the picture signal which causes uneven shading of the picture.
  • the above-mentioned characteristic of the transmitter tube made it diiiicult to eliminate transients or otherv undesired signals from the output thereof while obtaining maximum signal output.
  • an object of my invention to provide a method of and means for correcting, or otherwise controlling, the shading of a television picture.
  • I provide means for mixing with the picture signal saw-tooth and sine waves at the horizontal deecting frequency and harmonics thereof and saw-tooth and sine waves at the vertical deecting frequency and harmonics thereof. I have found that by mixing such correcting waves or signals in the proper phase and amplitude with the picture signal, a signal may be sent out from the transmitter which will produce a properly shaded picture at the receiver.
  • I provide a circuit including a clipping tube for removing undesired transients or the like from the output of the cathode-ray transmitter tube and, to facilitate their removal, I mix the above-mentioned correcting signals with the transmitter tube output at a point preceding the clipping tube.
  • FIG. 1 is a circuit and block diagram of a television transmitter embodying my invention
  • Fig. 2 is a circuit diagram of the shading amplier shown in Fig. l,
  • Fig. 3 is a circuit diagram of one of the ampliiers shown in Fig. l.,
  • Fig. 5 is a schematic diagram of a television receiver
  • Figs. 6 and 7 are views representing the possible shading of a picture appearing on the fluores cent screen of the cathode-ray tube receiver.
  • Figs. 8 to 17 inclusive are curves Which are referred to in explaining the invention.
  • the transmitter includes a cathode-ray transmitter tube l of the type described in an article by V. K. Zworykin published in the January, 1934, issue of the Proceedings ot the Institute of Radio Engineers.
  • a cathode-ray transmitter tube l of the type described in an article by V. K. Zworykin published in the January, 1934, issue of the Proceedings ot the Institute of Radio Engineers.
  • a second anode it consisting of a metallic coating on the inner surface of the enevelope 3 is provided for accelerating the electrons in the electron beam and for aiding in the focusing of the beam.
  • .lmosaic i3 of light-senstive elements is so positioned inside the envelope 3 that an optical image, formed by a suitable lens system l2, may be projected thereon whereby capacity elements which are associated with elements of the mosaic are charged in accordance with the intensity of light striking them.
  • This forms on the mosaic what may be referred to as an electrical image.
  • the mosaic is so positioned that it may be scanned by the electron beam.
  • incandescent lamps such as the lamp i6, which are supplied with current from the 60 cycle power line 25. While the light from such a source varies periodically in intensity whereby the light striking the mosaic I3 causes a hum component in the picture signal, this eiect may be compensated for in my system.
  • the mosaic may be constructed in various ways.
  • a mica sheet l5 has a metallic coating or signal plate Il formed on the back side and the mosaic I3 formed on the front side which consists of a very large number of minute silver globules each of which is photo- The tube l sensitized by means of caesium.
  • the light-sensitive silver globules are insulated from each other and each globule has a certain amount of capacity to the metallic coating I1.
  • Il In order to scan the mosaic with the electron beam deilecting coils Il may be provided for deiiecting the electron beam vertically and deilecting plates 2I provided for defiecting the beam horizontally.
  • a high voltage power supply unit 2l is provided for supplying the various electrodes oi the cathode-ray tube I with the proper voltage.
  • 'I'he input circuit of the power supply unit 2l is connected to a suitable power source, such as a 60- cycle power line 25, while the output circuit is connected to a voltage divider 21.
  • 'I'he cathode 5 is connected to a suitable point on the voltage divider 21 near its negative end, while the control grid 1 is connected to a point on the voltage divider 21 which is negative with respect to the cathode 5.
  • the first and second anodes 9 and II, respectively, are connected to points on the voltage divider which are positive with respect to the cathode l.
  • a voltage impulse generator 29 is provided which may be the same as that described and claimed in my copending application Serial No. 728,147, filed May 29, 1934, and assigned to the Radio Corporation of America.
  • the impulses are generated by means of a rotatable disc having suitable openings therein through which light may pass to strike a photoelectric cell, the disc being driven by a synchronous motor.
  • the synchronous motor (not shown) is supplied through conductors Il with current from the 60cycle line 25.
  • the generator 29 supplies vvertical detlecting impulses through a conductor 33 to a vertical deilecting circuit 35 which supplies a saw-tooth current to the deflecting coils I9.
  • Horizontal defiecting impulses are supplied through a conductor 31 to a horizontal deflecting circuit l! which supplies saw-tooth voltage waves to the deilectin'g plates 2
  • the vertical deflecting impulses occur 60 times per second, while the horizontal deilecting impulses occur '1290 times per second to lprovide 121% lines per picture, whereby the so-called interlaced scanning is produced.
  • picture signals will appear across a resistor 4I which is connected be- ⁇ tween the signal plate I1 and ground.
  • the frequency of the vertical deflecting impulses it is desirable that they occur at the same frequency as that of the power line 25 so that the uneven shading of the picture, due to the use ⁇ of the alternating current light source I8, will remain stationary on the picture.
  • the vimpulse generator 29 also supplies blanking impulses which are transmitted through a conductor 49 and a buil'er resistor 5I to a suitable point in the amplifier l5. It also supplies synchronizing impulses 5l through a conductor and a butler resistor to the output circuit of the Afrom the other bus bar.
  • buffer resistor is used in the preceding paragraph and will be used in the following paragraphs with reference to a resistor which is employed for the purpose of preventing one circuit from short-circuiting another circuit or otherwise rendering it ineective.
  • the buer resistors are employed largely for the purpose of causing voltages of different wave shapes and frequencies to add to give a composite wave of the desired shape.
  • Fig. 1 it has been found that usually the appearance of the picture at the receiver'is similar to the view in Fig. 6. That is, one corner of the picture will be darker than the rest of the picture.
  • I provide a shading circuit by means of which the picture at the receiver may be given a substantially uniform shading.
  • the main portion of the shading circuit is shown enclosed by the dotted rectangle.
  • This portion of the shading circuit supplies to a shading amplifier 51 saw-tooth waves occurring at' the horizontal and vertical deiiectingfrequencies, sine waves of the horizontal and vertical deflecting frequencies, and the second harmonics of these sine waves.
  • the output of the shading amplifier 51 is impressed through a buffer resistor I! upon the input circuitv of the ampliiler I5 where the saw-tooth waves and the sine waves are mined with the picture signal.
  • the saw-tooth waves of the horizontal de- 'iiecting frequency are supplied from the horizontal deilecting circuit 39 through a conductor IIv and through a coupling condenser 63 and buil'er resistor 65 to a potentiometer resistor l1 which is grounded at one end.
  • 'Ihe saw-tooth voltage wave is taken oil' the potentiometer 81 through a slideable contact 89 and transmitted through a resistor 1I to a switch arm 1I which may be connected either to a bus bar 15 or to a bus bar 11.
  • the shading amplifier 51 comprises three vacuum tubes 1s, II and 83 which maybe' of the suppressor grid type. These ampliiler tubes are connected in cascade in a conventional manner by means of resistance coupling,
  • each tube being provided with the ⁇ proper bias from a self-biasing resistor.
  • the plate circuit of the tube 209 also includes a peaking resistor 2
  • This impulse causes the control grid of the tube 204 to become more positive whereby the condenser 2
  • the voltage appearing across the condenser 2 I 5 and the peaking resistor 2 I3 is a sum ofthe sawtooth voltage appearing across the condenser 2li and a square top voltage appearing across the peaking resistor 2
  • 3 is provided because an impulse component must be added to the sawtooth wave to produce a flow of saw-tooth current in the deflecting coils, this being necessary because of the inductive reactance oi' the deiiecting coils. Since it is generally desirable to round of! the top of the saw-tooth wave for varying the i velocity of the vertical deflection, the input circuit of the amplifier tube 225 includes a resistor 221 and a condenser 229 connected in series whereby the impedance of the input circuit is greater for low frequencies than for high frequencies. The condenser 229 is shunted by a variable resistor 23
  • a television receiver for receiving pictures sent out from the transmitter illustrated in Fig. 1.
  • the television receiver comprises a radio receiver 233 and a separating circuit 235 which separates the picture signals (including the shading signals) from the vertical and horizontal synchronizing impulses and which also separates the vertical synchronizing impulses from the horizontal synchronizing
  • the picture and shading signals areimpulses. passed through a picture amplier 231 and impressed upon the control grid 220 oi' a cathoderay receiver tube 24
  • which ⁇ is illustrated is of a well known type comprising an evacuated envelope 242 having an electron gun therein consisting of an indirectly heated cathode 245, the
  • a second anode 249 consisting of a metallic coating on the inner surface oi' the envelope 24S is provided for accelerating the electrons in the electron beam and for aiding in the focusing of the beam.
  • is provided at theend of the tube where it may be scanned by the electron beam for producing a picture.
  • deilecting coils 252 and255. respectively may be provided.
  • the horizontal synchronizing impulses are impressed upon a horizontal deecting circuit 251 which supplies to the horizontal deecting coils 252 a saw-tooth current under the control of the synchronizing impulses.
  • a horizontal deecting circuit 251 which supplies to the horizontal deecting coils 252 a saw-tooth current under the control of the synchronizing impulses.
  • 'I'he vertical synchronizing impulses are supplied to a vertical deflecting lcircuit 258 which supplies saw-tooth current to the vvertical deilecting coils 255, this current being under the control of the vertical synchronizing impulses whereby the electron beam in the cathode-ray tube is caused to scan the uorescent screen in synchronism with the scanning of the mosaic I2 at the transmitter.
  • FIGs. 6 and "I are views of the end of the tube 24
  • a monitor receiver is provided as indicated at 258 in Fig. 1.
  • the end of the receiver tube is indicated at 260, the shading on the fluorescent screen being the same as shown in Fig. 6. Except that the radio receiver is omitted. the monitor receiver is the 'same as the receiver illustrated in Fig. 5.
  • Fig. 6 has the characteristic illustrated by the curve 269A in Fig. 8.
  • the picture signals for each horizontal scanning line are represented by the portions z, while the portions y of the curve, located between successive horizontal line signals, are undesired transient signals which are produced during the horizontal return line period.
  • the cathode-ray is being returned to begin the next scanning of the picture.
  • the sawtooth voltage waves shown in Figs. 9 and 1l are mixed with the picture signal, the saw-tooth waves shown in Fig. 9 occurring at the horizontal scanning frequency and the saw-tooth waves shown in Fig. l1 occurring at the frame frequency.
  • the lirst saw-tooth voltage corrects the picture signal to produce a signal such as shown in Fig. 10, while the other saw-tooth voltage further corrects the picture signal to produce the signal shown in Fig. 12. this curve having a zero axis which is horizontal.
  • the signal appears in reversed phase in the output circuit of the ainplier E65 as indicated. by the curve ZlS (Fig. 3) and is then impressed upon the last ampliier 25'?. pulses and superimposed transients are of considarable magnitude and are in a negative direction, they drive the tube Edi beyond the cut-oli point, indicated by the dotted line 2id, and the transients are clipped ou to produce a signal in the output the amplier which is represented by the curve fll shown in Fig. 3 and in Fig. l5.
  • the procedure is as follows: .An operator at the transmitting station so adjusts the monitor that the picture appearing on the tubeit is rather dim whereby any irregularities in shading will be readily apparent. He then closes such bus bar switches, 13,
  • a cathode-ray transmitter tube may be operated at its maximum sensitivity or eiliciency and, at the same time, a properly shaded picture obtained at the receiver. Also, the signals impressed upon the receiver will be free from transient signals and the like which would impair the quality of the picture.
  • a cathode-ray picture transmitter tube of the type comprising a mosaic of electron emissive capacity elements which are to be scanned by an electron beam to produce pic'- ture signals and undesired spurious signals'which unevenly shade the picture, means for producing shading signals of a. predetermined wave shape, and means for mixing said shading signals with said picture signals for balancing out said spurious signals, said shading signals having the characteristic that they affect the relative illumination in different parts of the picture.
  • a cathode-ray picture transmitter tube of the type comprising a mosaic of electron emssive capacity elements which are to be scanned by an electron beam to produce picture signals and undesired spurious signals which unevenly shade the picture, means for producing signalsroi saw-tooth wave shape and signals o sine Wave shape with said picture signals. and means for mixing all of said signals for balancing out said spurious signals to produce a correctly shaded picture.
  • means for generating picture signals and undesired spurious signals which unevenly shade a picture reproduced by said picture signals means for generating saw-tooth wave signals and sine wave signals which occur simultaneously with said picture signals, means for so adding all of said signals as to balance out said spurious signals, and
  • a cathode-ray transmitter tube which generates picture signals of a character which produce .a picture of uneven shading at the receiver due to spurious signals which unevenly shade the picture, and means located at the transmitter for balancing out at least part of said spurious signals to correct said uneven shading, said means comprising means for generating sawtooth and sine wave voltages which occur simultaneously with said picture signals and for adding them to said picture signals.
  • a cathode-ray transmitter tube of the type including a mosaic of electron-emissive capacity elements, means for sweeping the cathode-ray horizontally across said mosaic at a horizontal deilecting frequency, means for deilecting said cathode-ray simultaneously in a vertical direction at a vertical deflecting frequency whereby said mosaic is scanned periodically by said cathode-ray to produce picture signals and undesired spurious signals which unevenly shade the picture, means for producing a correcting signal which occurs simultaneously with said picture signals, said correcting signal having a fundamental frequency equal to one of said deflecting frequencies, and means for so ad- :ling said correcting signal to said picture signals as to balance out said spurious signals.
  • a cathode-ray transmitter tube of the type including a mosaic of electron emissive capacity elements, means for sweeping the cathode-ray horizontally across said mosaic at a horizontal deflecting frequency, means for deflecting said-cathode-ray simultaneously in a vertical direction at a vertical deecting frequency whereby said mosaic is scanned periodically by said cathode-ray to produce picture signals and undesired spurious signals whichl unevenly shade the picture, and means for adding at least two correcting signals to said picture signals for balancing; out said spurious signals.
  • one of said correcting signals having a fundamental frequency equal to said horizontal deflecting frequency
  • the other of said correcting signalsv having a fundamental frequency equal to said vertical deecting frequency, said two correcting signals having substantially a sawtooth wave form.
  • a cathode-ray transmitter tube of the type including a mosaic of electron emissive capacity elements, means for sweeping the cathode-ray horizontallyacross said mosaic at a horizontal deflecting frequency,-
  • a cathode-ray transmitter tube of the type including a mosaic of electron emissive capacity elements, means for sweeping the cathode-ray horizontally across said mosaic at a horizontal deilecting frequency, means for deilectingsaid cathode-ray'sixnultaneously in a vertical direction at a vertical deecting frequency whereby said mosaic is scanned periodically by said cathode-ray to produce picture signals and undesired spurious signals which unevenly shade the picture, and means for adding a plurality of correcting signals to said picture signals for balancing out said spurious signals, two of said correcting signals having a sawtooth wave form and two of them having a sine wave form, one saw-tooth signal and one sine wave signal having a fundamental frequency equal to said vertical denecting frequency, and another saw-tooth signal and a sine wave signal having a vfundamental frequency equal to said horizontal deflecting frequency.
  • Apparatus according to claim characterized in that means is provided for shifting the phase of said correcting Signal.
  • a cathode-ray amavis transmitter tube having an output circuit and including means for producing an electrical image of the picture to be transmitted, said tube having a vertical deecting device and a horizontal defiecting device whereby the cathoderay may be deflected vertically and horizontally simultaneously to produce picture signals and undesired spurious signals which unevenly shade the picture, said spurious signals having one sawtooth component occurring at the vertical deecting frequency and having another saw-tooth component occurring at the horizontal deiecting frequency, means for supplying a saw-tooth electrical wave occurring at the vertical deilecting frequency to said vertical deilecting device, means for supplying a saw-tooth electrical wave occurring at the horizontal deecting frequency to said horizontal defiecting device, and means for adding signals derived from said last two means to the signals appearing in said output circuit for balancing out said spurious signals.
  • a cathode-ray transmitter tube having an output circuit and including means for producing an electrical image of the picture to be transmitted, said tube having a vertical deflecting device and a horizontal deiiecting device whereby the cathoderay may be deflected vertically and horizontally simultaneously to produce picture signals and undesired spurious signals which unevenly shade the picture, said spurious signals having a sawtooth component occurring at the vertical deflecting frequency and having another sawtooth compcnent occurring at the horizontal deflecting frequency and also having sine wave components, means for supplying a saw-tooth electrical wave occurring at the vertical deilecting frequency to said vertical deilecting device, means for supplying a saw-tooth electrical wave occurring at the horizontal deflecting frequency to said horizontal deflecting device, and means for adding saw-tooth and sine wave signals derivedfrom said last two means to the signals appearing in said output circuit for balancing out said spurious signals.
  • a cathode-ray tube generates an output signal which includes picture signals and transients and in which the zero axis of said signals varies as the signals are generated due to undesired spurious signals which unevenly shade the picture
  • the method of eliminating said transients which consists in mixing correcting signals with said output signal, said correcting signals having a. wave shape such as to balance out said spurious signals and correct for the said variation in the zero axis, mixing electrical impulses with said output signal, said impulses occurring at the same time as said transients and being of suicient magnitude to remove the transients from the region of said picture signals. and clipping said transients from the resulting signal.
  • a cathode-ray transmitter tube of the type including a mosaic ci' electron emissive capacity elements, means for sweeping the cathode-ray horizontally across said mosaic at a horizontal deecting frequency, means for deflecting said cathode-ray simultaneously in a vertical direction at a vertical deflecting frequency whereby said mosaic is scanned periodically by said cathode-ray to produce picture signals and undesired spurious signals which unevenly shade the picture, means for producing simultaneously with said picture signals a sine wave signal which has a frequency equal to the second harmonic of one of said deilecting frequencies, and means for adding said sine wave signal to said picture signal for balancingout said spurious signals.
  • Apparatus according to claim 16 characterized in that means is provided 'for shifting the phase of said sine wave.
  • Apparatus according to claim 5 characterized in that means is provided for reversing the polarity of said correcting signal.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Details Of Television Scanning (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
US750055A 1934-10-26 1934-10-26 Television system Expired - Lifetime US2166712A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
BE411923D BE411923A (enrdf_load_stackoverflow) 1934-10-26
US750055A US2166712A (en) 1934-10-26 1934-10-26 Television system
FR793594D FR793594A (fr) 1934-10-26 1935-08-09 Perfectionnements aux systèmes de télévision
GB27805/35A GB463967A (en) 1934-10-26 1935-10-08 Improvements in or relating to television transmitters
DER94572D DE767558C (de) 1934-10-26 1935-10-27 Schaltungsanordnung fuer speichernde Kathodenstrahl-Bildabtaster

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US750055A US2166712A (en) 1934-10-26 1934-10-26 Television system

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US2166712A true US2166712A (en) 1939-07-18

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US750055A Expired - Lifetime US2166712A (en) 1934-10-26 1934-10-26 Television system

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US (1) US2166712A (enrdf_load_stackoverflow)
BE (1) BE411923A (enrdf_load_stackoverflow)
DE (1) DE767558C (enrdf_load_stackoverflow)
FR (1) FR793594A (enrdf_load_stackoverflow)
GB (1) GB463967A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2445040A (en) * 1943-05-13 1948-07-13 Rca Corp Dark spot corrector
US2532063A (en) * 1946-09-07 1950-11-28 Rca Corp Position indicating system
US2552060A (en) * 1945-07-26 1951-05-08 Rca Corp Television circuits
US2581589A (en) * 1946-12-12 1952-01-08 Rca Corp Position indicating system
US2658104A (en) * 1949-12-30 1953-11-03 Du Mont Allen B Lab Inc Television shading signal and clamping circuit
US2753394A (en) * 1949-05-19 1956-07-03 Emi Ltd Television transmission systems
US2764698A (en) * 1942-11-23 1956-09-25 Arthur R Knight Control system
US2775644A (en) * 1950-10-14 1956-12-25 Soc Nouvelle Outil Rbv Radio Picture analysis and recording devices
US2890276A (en) * 1953-07-01 1959-06-09 Rca Corp Television control system
US4970598A (en) * 1989-05-30 1990-11-13 Eastman Kodak Company Method for correcting shading effects in video images
US4979042A (en) * 1989-05-30 1990-12-18 Eastman Kodak Company Apparatus for correcting shading effects in video images

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1271160B (de) * 1960-06-30 1968-06-27 Fernseh Gmbh Schaltungsanordnung zur ortsabhaengigen Veraenderung des Kontrastes eines Fernsehbildes
DE1247384B (de) * 1963-03-14 1967-08-17 Ibm Schaltung zum Ausfiltern von Impulsen

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE330275C (de) * 1919-05-07 1920-12-11 Hans Georg Moeller Dr Einrichtung zur Kompensation von Spannungsschwankungen einer Gleichtromquelle
DE475330C (de) * 1921-10-12 1929-04-22 Procedes W A Loth Soc Ind Des Einrichtung zur Beseitigung der bei drahtlosem Signalempfang durch den Zuendfunken oder das veraenderliche magnetische Feld des Zuendmagneten bei Verbrennungsmotoren entstehenden Stoerungen
GB268887A (en) * 1926-01-09 1927-04-11 Edward Herbert Trump Improvements in or relating to thermionic amplifiers
GB280645A (en) * 1926-08-19 1927-11-21 Willoughby Statham Smith Improvements in or relating to means for supplying electric current to thermionic valves
GB379552A (en) * 1931-10-23 1932-09-01 George William Walton Improvements in and relating to television, electrical transmission of pictures and the like
BE403568A (enrdf_load_stackoverflow) * 1933-01-28
BE401713A (enrdf_load_stackoverflow) * 1933-02-28

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2764698A (en) * 1942-11-23 1956-09-25 Arthur R Knight Control system
US2445040A (en) * 1943-05-13 1948-07-13 Rca Corp Dark spot corrector
US2552060A (en) * 1945-07-26 1951-05-08 Rca Corp Television circuits
US2532063A (en) * 1946-09-07 1950-11-28 Rca Corp Position indicating system
US2581589A (en) * 1946-12-12 1952-01-08 Rca Corp Position indicating system
US2753394A (en) * 1949-05-19 1956-07-03 Emi Ltd Television transmission systems
US2658104A (en) * 1949-12-30 1953-11-03 Du Mont Allen B Lab Inc Television shading signal and clamping circuit
US2775644A (en) * 1950-10-14 1956-12-25 Soc Nouvelle Outil Rbv Radio Picture analysis and recording devices
US2890276A (en) * 1953-07-01 1959-06-09 Rca Corp Television control system
US4970598A (en) * 1989-05-30 1990-11-13 Eastman Kodak Company Method for correcting shading effects in video images
US4979042A (en) * 1989-05-30 1990-12-18 Eastman Kodak Company Apparatus for correcting shading effects in video images

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DE767558C (de) 1952-12-08
BE411923A (enrdf_load_stackoverflow)
GB463967A (en) 1937-04-08
FR793594A (fr) 1936-01-27

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