US2247512A - Television video-frequency signaltranslating system - Google Patents

Television video-frequency signaltranslating system Download PDF

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Publication number
US2247512A
US2247512A US227629A US22762938A US2247512A US 2247512 A US2247512 A US 2247512A US 227629 A US227629 A US 227629A US 22762938 A US22762938 A US 22762938A US 2247512 A US2247512 A US 2247512A
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US
United States
Prior art keywords
signal
repeating
tube
amplitude range
channel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US227629A
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English (en)
Inventor
Harold M Lewis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems Aerospace Inc
Original Assignee
Hazeltine Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL65998D priority Critical patent/NL65998C/xx
Application filed by Hazeltine Corp filed Critical Hazeltine Corp
Priority to US227629A priority patent/US2247512A/en
Priority to GB22870/39A priority patent/GB535413A/en
Priority to FR859813D priority patent/FR859813A/fr
Application granted granted Critical
Publication of US2247512A publication Critical patent/US2247512A/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
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/20—Circuitry for controlling amplitude response
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G7/00—Volume compression or expansion in amplifiers
    • H03G7/02—Volume compression or expansion in amplifiers having discharge tubes
    • H03G7/04—Volume compression or expansion in amplifiers having discharge tubes incorporating negative feedback
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/20—Circuitry for controlling amplitude response
    • H04N5/202—Gamma control

Definitions

  • a film In photography a film is said to have a "gamma which deviates from unity in accordance with differences in the relative detail in the film for the brighter 'anddarker portions of the scene compared to other portions thereof- The same concept arises in television.
  • the gamma" of any reproduction is defined as the tangent of the stimulus-response curve plotted on a logarithmic scale. Obviously only where gamma is unity is there a linear relationship between the stimulus and response over the entire response range of the system.
  • a television video-frequency signal-translating channel comprising, signal repeating means having an adjustable repeating characteristic with respect to a part only of the amplitude range 01' a signal translated by the channel, a second signal-repeating means having anadjustable repeating ratio with respect to the total 0! the amplitude range.
  • signal repeating means having an adjustable repeating characteristic with respect to a part only of the amplitude range 01' a signal translated by the channel
  • a second signal-repeating means having anadjustable repeating ratio with respect to the total 0! the amplitude range.
  • Fig. 1 is a schematic diagram of a complete television signal-receiving system including a video-frequency amplifier embodying the present invention
  • Fig. 2 is a group of curves illustrating certain operating characteristics of the system of Fig. 1, to aid in the understanding of the invention
  • Fig. 3 is a circuit diagram of a modified form of the video-frequency amplifier of the present invention
  • Fig. 4 is a group of curves illustrating th operating characteristics of the circuit of Fig. 3.
  • the system there illustrated comprises a television receiver of the superheterodyne type including an antenna system in, II connected to a radiofrequency amplifier l2 to which there is connected in cascade, in the order named, an oscillator-modulator I3, an intermediate-frequency amplifier I4, a detector and A. V. C. supply It, a video-frequency amplifier indicated generally at l6 and embodying the present invention and a signal-reproducing device H, such as a cathode-ray reproducing tube.
  • a line-frequency scanning-wave generator [8 and a field-frequency scanning-wave generator l9 are also coupled to the output of th detector [5 and to the scanning elements of the signal-reproducing device.
  • the stages l2-l9, inclusive, excepting the videofrequency amplifier I6, may all be of conventional well-known construction so that detailed illustrations and descriptions thereof are unnecessary herein.
  • television signals intercepted by the antenna circuit Ill, ii are selected and amplified in the radio-frequency amplifier l2 and supplied to the oscillatormodulator l3, wherein they are converted to intermediate-frequency signals which, in turn, are selectively amplified in the intermediate-frequency amplifier l4 and delivered to the detector I.
  • the modulation components oi the signal are derived by the detector I and are supplied to the video-frequency amplifier l8, wherein they are amplified and translated by the apparatus of the present invention, as will be presently further described, and from which they are applied to a brilllancy-control element of the reproducing device II.
  • the intensity of the scanning beam of device I1 is modulated or controlled in accordance with the video-frequency voltages impressed upon the control elements in the usual manner.
  • a control-bias voltage developed by the A. V. C. supply i5 and proportional to the average carrier amplitude, independent of its light modulation, is supplied in the usual manner to control grids of tubes in the stages l2-ll, inclusive, for maintaining the signal-output amplitude of the amplifier I4 within a relatively narrow range for a wide range of received signal intensities.
  • the modulation si nal is also applied to the generators. l8 and I9 and the synchronizing components of the signal are utilized therein to synchronize the operations of these generators with the corresponding scanning apparatus at the transmitter.
  • Saw-tooth current or voltage scanning waves are generated by the generators I8 and I8 and these waves are applied to the scanning elements of the device I! to produce scanning fields, thereby to deflect the scanning beam in two directions normal to each other so as to trace successive series oi parallel lines or fields on the target of the reproducing device to reconstruct the image.
  • the video-frequency amplifier i6 is designed according to the present invention and comprises a signal-translating channel including repeating means, for example, a pair of vacuum-tube amplifiers and 2
  • the wntrol grid of the tube 20 is connected directly to the output circuit of the detector l5, while an adjustable unbypassed resistor 22 is included in its cathode circuit.
  • the control grid-cathode circuit of the tube 2] is connected across resistor 22, while an adjustable-bias battery 23 is included in its cathode circuit.
  • a common anode circuit is provided for the tubes 20 and 2
  • the input circuit of the reproducing device i1 is connected across the load circuit 24, 25 by way of a suitable coupling condenser 26. Operating potentials are supplied to the screen and anodes of the tubes from suitable sources indicated at +80 and +3.
  • the operation of the amplifier or video-frequency translating channel l6 may best be described with reference to the curves of Fig. 2, in which the curves B represent the plate current grid-voltage characteristics of the tubes 20 and 2i.
  • Tube 20 has a substantially linear gridvoltage plate current characteristic as represented by the curve Ipi which corresponds to the condition that the value of resistor 22. is reduced to zero. Therefore, with an applied signal having a wave form such as indicated at V the output voltage of the tube 2! alone is of a substantially undistorted wave form, as indicated at V0.
  • Curve I' i illustrates the corresponding characteristic of tube 2
  • Curve In represents the eilective gridvoltage plate current characteristic of the tube 2] and is similar to curve 191 of tube 20 except that its cathode-bias battery 22 is normally adjusted to set the cutoi! point at a predetermined value of signal voltage greater than that oi the tube 20 so that only a predetermined desired upper portion oi the amplitude range or an applied signal is repeated by the tube 2i.
  • emitting grid-voltage plate current characteristic is used to denote the characteristic with respect to a given reference signal-input voltage V taking into consideration the fact that the actual amplitude 01 the signal input to tube 2
  • the value of resistor 22 is adjusted to impart to the tube 20 the characteristic I' i and to impress on tube 2
  • a signal proportional to the value of the resistor 22 the eflective composite inputvoltage plate current characteristic for the two tubes operating in parallel is illustrated by the curve I i-i-I i, while the curve V'o illustrates the resultant output voltage of the channel with the tubes adjusted to have the characteristics illustrated.
  • the portion of the signal voltage corresponding to white will be expanded. While the character-' istics of both of the tubes 20 and 2
  • the unit I 6 of Fig. 1 comprises a signal-repeating means including vacuum-tube amplifier 2
  • comprises the adjustable tap on resistor 22 for adjusting the signal-input amplitude to the tube 2i and the amplifier 2
  • the vacuum-tube amplifier 20 comprises a second signal-repeating means effectively having an adjustable repeating ratio, by virtue of adjustable cathode resistor 22, with respect to the total of the amplitude range of the translated signal, as represented by curves Ipl and P 1 of Fig. 2.
  • the adjustable tap of resistor 22, therefore, comprises a single control means for simultaneously effecting the two above-mentioned adjustments in opposite senses.
  • Resistor 24 is included in the output circuits of both of tubes 2
  • the relatively high repeating ratios for the two tubes output of the channel is aflected by both of the adjustments.
  • an amplifier or signal-translating channel Ilia which may be substituted for the amplifier i6 oi! Fig. 1.
  • the modified arrangement includes tubes 20a and 2ia having a common output circult 24a, 25a and a biasing battery 23a for tube 2Ia, all of which are similar to the corresponding' elements of the amplifier i6.
  • no resistor is included in the cathode circuit of the tube 20a; the control grid of the tube 2la being connected directly with the control grid of the tube 20a to the output circuit of the preceding stage of the system.
  • an adjustable voltage source such as a battery 21
  • a suitable unicontrolled device indicated at U is provided connected, for example, to the adjustable tap on the batteries.
  • Curve V0 represents the composite out,- put voltage of the amplifier
  • the curve Ip1+Ip2 shown at B in Fig. 4 has an intermediate portion, corresponding to the middle of the amplitude range of the translated voltage, which has a very gradual slope while the end portions have a very steep slope corresponding to a high repeating ratio.
  • both end portions of the amplitude range of the translated signal in other words, both the black and the white portions, are expanded, while the intermediate portion is contracted.
  • the curves Ipl and Ipz may be shifted, as indicated in Fig. 4 by the dot-dash lines, so that the portion of gradual slope in the resultant or composite curve is correspondingly adjusted, as indicated in Fig. 4, while the output voltage over-all amplitude range remains unchanged.
  • the curve V'o represents the wave form of the over-all output voltage when such adjustments have been made.
  • a television video-frequency signal-translating channel comprising, a pair of vacuumtube amplifiers, an input circuit for one of said amplifiers including an unbiased. cathode resistor, an input circuit for the other of said tubes connected across said resistor, said tubes having mutual conductance characteristics and being so biased that said one tube repeats the signal input thereto over its entire amplitude range and said other tube repeats the signal input thereto over only a part of its amplitude range, means for adjusting said resistor simultaneously to adjust the negative regeneration of the first of said tubes and the signal input of the second of said tubes, and a common anode circuit for said amplifiers.
  • a television video-frequency signal-translating channel comprising, signal-repeating means having an adjustable repeating characteristic with respect to a part only of the amplitude range of a signal translated by said channel. a second signal-repeating means having an adjustable repeating ratio with respect to the total 01' said amplitude range, a single control means for simultaneously eil'ecting adjustments of said two signal-translating means in opposite senses, and an output circuit so coupled to said repeating means that the signal output 01 said channel is aflectcd by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a signal-repeating means including means for adjusting the signal-input amplitude thereto for adjusting a repeating characteristic with respect to a part only of the amplitude range of the signal translated by said channel, a second signal-repeating means having an adjustable repeating ratio with respect to the total of said amplitude range, a single control means for simultaneously effecting adjustments of said two signal-repeating means in opposite senses, and an output circuit so coupled to said repeating means that the signal output of said channel is afiected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a vacuum-tube amplifier having an adjustable repeating characteristic with respct to a part only of the amplitude range oi the signal translated by said channel, a second 'vacuum-tube amplifier having an adjustable repeating ratio with respect to the total of said amplitude range, a single control means for simultaneously effecting adjustments of said two amplifiers in opposite senses, and an output circuit so coupled to said amplifiers that the signal output of said channel is afl'ected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a vacuum-tube amplifier having such a mutual conductance characteristic and so biased as to have an adjustable repeating characteristic with respect to a part only of the amplitude range of a signal translated by said channel, a second vacuumtube amplifier having such a mutual conductance characteristic and so biased as to have an adjustable repeating ratio with respect to the total of said amplitude range, a single control means for simultaneously eifecting adjustments of said two vacuum-tube amplifiers in opposite senses. and an output circuit so coupled to said amplifiers that the signal output of said channel is affected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, signal-repeating means having an adjustable repeating characteristic with respect to apart only of the amplitude range of a signal translated by said channel, a second signal-repeating means having an adjustable repeating ratio with respect to the total of said amplitude range, a single control means for simultaneously efiecting adjustments of said two signal-translating means in opposite senses, and an output circuit coupled to said amplifiers, said adjustments being so proportioned that the maximum signal output of said channel remains substantially constant for all said adjustments.
  • a television video-frequency signal-translating channel comprising, a signal-repeating means having an adjustable repeating characteristic with respect to a part only of the amplitude range of the signal translated by said channel and having a relatively high repeating ratio for one predetermined portion 01 the total signal-amplitude range with respect to the remainder of said range, a second repeating means having a relatively high repeating ratio for a dverent predetermined portion of the total of. said amplitude range, a single control means for simultaneously effecting adjustments of said two signal-translating means in opposite senses, and an output circuit so coupled with said repeating means that the signal output of said channel is affected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a signal-repeating means having an adjustable repeating characteristic with respect to a part only of the amplitude range 01 the signal translated by said channel and having a relatively high repeating ratio for one predetermined portion oi! the total signal-amplitude range with respect to the remainder of said range, a second repeating means having an adjustable repeating ratio for a different predetermined portion of the total of said amplitude range, said signal-repeating means having relatively high repeating ratios at opposite ends of the total amplitude range, a single control means for simultaneously efiecting adjustments of said two signal-repeating means in opposite senses, and an output circuit so coupled with said repeating means that the signal output of said channel is affected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a vacuum-tube amplifier having an adjustable repeating characteristic with respect to a part only of the amplitude range of the signal translated by said channel, a second vacuum-tube amplifier having an adjustablerepeating ratio with respect to the total of said amplitude range, a single control means for simultaneously effecting adjust ments of said two signal-translating means in opposite senses, and an output circuit so coupled to said repeating means that the output circuits of said amplifiers are in parallel and the signal output of said channel is affected by both said adjustments.
  • a television video-frequency signal-translating channel comprising, a vacuum-tube amplifier having an adjustable repeating ratio with respect to a part only of the amplitude range of the signal translated by said channel and so biased that said amplifier is cut off for input voltages below a predetermined amplitude value, a second vacuum-tube amplifier having an adjustable repeating ratio with respect to the total amplitude range and so biased that said second amplifier is saturated for input voltages above a predetermined value, a single control means for simultaneously effecting adjustments of said two amplifiers in opposite senses, and an output circuit so coupled to said amplifiers that the signal output of said channel is affected by both said adjustments.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Picture Signal Circuits (AREA)
  • Television Receiver Circuits (AREA)
US227629A 1938-08-31 1938-08-31 Television video-frequency signaltranslating system Expired - Lifetime US2247512A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL65998D NL65998C (enrdf_load_stackoverflow) 1938-08-31
US227629A US2247512A (en) 1938-08-31 1938-08-31 Television video-frequency signaltranslating system
GB22870/39A GB535413A (en) 1938-08-31 1939-08-08 Television video-frequency signal-translating system
FR859813D FR859813A (fr) 1938-08-31 1939-08-31 Amplificateur de fréquence de vision

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US227629A US2247512A (en) 1938-08-31 1938-08-31 Television video-frequency signaltranslating system

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US2247512A true US2247512A (en) 1941-07-01

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US227629A Expired - Lifetime US2247512A (en) 1938-08-31 1938-08-31 Television video-frequency signaltranslating system

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US (1) US2247512A (enrdf_load_stackoverflow)
FR (1) FR859813A (enrdf_load_stackoverflow)
GB (1) GB535413A (enrdf_load_stackoverflow)
NL (1) NL65998C (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2552588A (en) * 1947-04-26 1951-05-15 Columbia Broadeasting System I Gamma control circuit
US2594870A (en) * 1945-11-29 1952-04-29 Us Navy Indicator
US2668188A (en) * 1949-12-19 1954-02-02 Rubert S Naslund Television gamma test method and apparatus
US2692299A (en) * 1948-12-11 1954-10-19 Westinghouse Electric Corp Image contrast intensifier

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE956587C (de) * 1953-06-26 1957-01-24 Fernseh Gmbh Anordnung zur Gradationsentzerrung bei Fernsehsendeanlagen
DE1011784B (de) * 1954-12-08 1957-07-04 Eisenwerke Muelheim Meiderich Verfahren zum Beobachten, UEberwachen und Regeln der Schmelzvorgaenge in metallurgischen Schmelz- oder Sinteroefen
DE1088534B (de) * 1956-10-20 1960-09-08 Grundig Max Gradationsregler fuer Fernsehempfaenger

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2594870A (en) * 1945-11-29 1952-04-29 Us Navy Indicator
US2552588A (en) * 1947-04-26 1951-05-15 Columbia Broadeasting System I Gamma control circuit
US2692299A (en) * 1948-12-11 1954-10-19 Westinghouse Electric Corp Image contrast intensifier
US2668188A (en) * 1949-12-19 1954-02-02 Rubert S Naslund Television gamma test method and apparatus

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Publication number Publication date
FR859813A (fr) 1940-12-30
NL65998C (enrdf_load_stackoverflow)
GB535413A (en) 1941-04-09

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